S. Irani, "Page Replacement with Multi-Size Pages and Applications to Web Caching," Proc. 29th Ann. ACM Symp. Theory of Computing (STOC '97), pp. 701-710, 1997.  Home/Search   Document Not in Database   Summary   Related Articles   Check

....of our ongoing work in Section V. II. RELATED WORK File size has long been used as a metric in a wide range of policies and algorithms used to efficiently deliver WWW content. Irani was first to observe that caching policies which do not take file size into account do not work well in practice [9]. Modern streaming media caching algorithms such as Resource Based Caching consider both the impact of file size and required delivery bandwidth in making cache insertion and replacement decisions [15] Size based scheduling policies at Web servers use the size of the requested file to prioritize ....

S. Irani. Page Replacement with Multi-size Pages and Applications to Web Caching. In Proceedings of the 29th Annual ACM Symposium on Theory of Computing, May 1997.

....not only its next occurrence, but also the amount of area that the task will free up upon removal from the chip. This problem has direct applications in web caching where pages have different sizes and request frequencies. A complete discussion along with effective algorithms can be found in [15]. Moreover, although we suppose to have the complete information about the application DFG, many real life applications do not conform to this assumption (the online version of the problems) For instance, a web caching policy has almost no information about the next page that a user might ....

S. Irani. "Page Replacement with Multi-Size Pages and Applications to Web Caching". Algorithmica, 33(3):384--409, 2002.

....marking algorithms. Deterministic Marking Algorithms Randomized Marking Algorithms Type 1 2k 1 2(2H k 1) Type 2 2k 1 4H k Type 3 k k Table 1: Upper bounds on the competitive ratios of all deterministic or randomized marking algorithms. Recent related work. As in the case of a single cache [15, 28, 29], the connection caching model can be generalized by allowing connections to have varying sizes and fetching costs. In the HTTP over TCP context, sizes may correspond to number of socket bu ers allocated. Establishment costs may capture the user perceived latency caused by ....

S. Irani. Page replacement with multi-size pages and applications to web caching. In Proc. 29th Annual ACM Symposium on Theory of Computing. ACM, 1997.

....problems The plain LRU, LFU, and LRFU algorithms are designed for pages with equal sizes and miss costs. Web objects, however, vary significantly in both size and cost of a miss. This motivated the development of cache replacement algorithms that account for varying page sizes and fetching costs [5, 8, 3, 4]. Experiments showed that the optimally competitive Landlord algorithm performs well on Web caching sequences [8, 3] Other experiments, however, show that it can be outperformed by perfect LFU [2] A natural open problem is thus to extend our results to this more general model. That is, develop ....

S. Irani. Page replacement with multi-size pages and applications to web caching. In Proc. 29th Annual ACM Symposium on Theory of Computing. ACM, 1997.

....web environment exhibit di erent characteristics than in traditional operating systems caches. One well recognized di erence is the variability in sizes and fetching costs of di erent resources (pages) and indeed, replacement policies that incorporate these parameters were suggested and evaluated [7, 15, 23, 22]. As is the case in traditional paging, individual requests remain hard to predict. We focus on two separate predictable aspects of the trac in the web environment. The rst is the usage levels experienced by large proxy and (typically) web servers. The second is distinct per page characteristic ....

....next request time of the requested page is provided. When page sizes and fetching costs are uniform, this information suces to perform optimally, by simply evicting the page to be requested furthest in the future [4] However, when fetching costs and sizes vary, this information is insucient [15]. Intuitively, with uniform costs there is a total order on the value of all cached pages (according to their next request time) With varying costs, the relative value of cached pages depends on future requests for pages not yet seen. As a simple example, suppose that the replacement algorithm ....

[Article contains additional citation context not shown here]

S. Irani. Page replacement with multi-size pages and applications to web caching. In Proc. 29th Annual ACM Symposium on Theory of Computing. ACM, 1997.

....time the cache contains a set of pages of total size no greater than k. When a page is requested, if it is cached then the request is a hit. Otherwise it is a miss and the caching algorithm may evict a subset of pages in order to make room for caching the currently requested page. Similar to Irani [7], we charge the algorithm by the respective fetching cost f(p) upon each decision to evict or not to cache a page p. This cost measure differs by an additive constant (incurred by all algorithms) from charging for the fetching cost upon each miss. The goal of a caching algorithm is to minimize ....

....does not necessarily force p into the cache. Forcing a page into the cache is a realistic model of operating system caches but the actual scenario in most web caches is that the page does not have to enter the cache in order to serve the request. This assumption is consistent with that of Irani [7] and is the only detail in which our variant differs from the one considered by Young [15] We prove the following: Theorem 1 The cost of greedy dual size is at most times the cost of the optimal strategy that uses a cache of size h for every h k. We prove this theorem in the next section. ....

[Article contains additional citation context not shown here]

S. Irani. Page replacement with multi-size pages and applications to web caching. In Proc. 29th Annual ACM Symposium on Theory of Computing. ACM, 1997.

....that may occur when requests and their responses are routed within the network. We also remark that cost models have been adopted in uniprocessor caching systems to model scenarios in which the costs incurred in the retrieval of objects on cache misses may vary from one object to another [10, 19, 33]. With regard to uniprocessor caching schemes, recent research has addressed the challenge of designing cache replacement policies that take into account the di ering costs incurred in the retrieval of objects on cache misses. This has led to studies formulating generalizations of the traditional ....

....addressed the challenge of designing cache replacement policies that take into account the di ering costs incurred in the retrieval of objects on cache misses. This has led to studies formulating generalizations of the traditional uniprocessor caching problems that account for the di ering costs [10, 19, 33]. In a recent experimental study [21] Korupolu and Dahlin evaluate the practical performance of several placement and replacement algorithms for cooperative caching. Their simulation experiments demonstrate that, in practice, both our greedy placement algorithm as well as our amortizing ....

S. Irani. Page replacement with multi-size pages and applications to Web caching. In Proceedings of the 29th Annual ACM Symposium on Theory of Computing, pages 701-710, May 1997.

.... (see comment below) Irani considered two special cases of le caching: when the costs are either all equal (the goal is to minimize the number of retrievals) and when each cost equals the le size (the goal is to minimize the total number of bytes retrieved) For these two cases, Irani [7] gave O(log 2 k) competitive randomized on line algorithms. Comment: the importance of sizes and costs. File caching is important for world wide web applications. For instance, in browsers and proxy servers remote les are cached locally to avoid remote retrieval. In web servers, disk les are ....

....the importance of sizes and costs. File caching is important for world wide web applications. For instance, in browsers and proxy servers remote les are cached locally to avoid remote retrieval. In web servers, disk les are cached in fast memory to speed response time. As Irani points out (see [7] and references therein) le size is an important consideration; caching policies adapted from memory management applications that don t take size into account do not work well in practice. Allowing arbitrary costs is likely to be important as well. In many cases, the cost (e.g. latency, total ....

Sandy Irani. Page replacement with multi-size pages and applications to Web caching. Proceedings of the Twenty-Ninth Annual ACM Symposium on Theory of Computing, pages 701-710, El Paso, Texas, 4-6 May 1997.

.... these methodologies and have evaluated several designs in comparison with conventional cache management algorithms (Williams et al. 1996) It is sometimes possible to establish tight bounds on the performance of cache replacement policies independent of workload (client document request patterns (Irani 1997; Sleator and Tarjan 1985) This approach, however, yields performance guarantees far weaker and more pessimistic than the observed performance of most reasonable removal policies under real workloads. In order to evaluate the relative performance of practical caching schemes we must therefore ....

.... documents that are no longer requested (Kelly, Jamin, and MacKie Mason 1999) Extensive experiments have shown that weighted LFU with aging usually delivers more aggregate value to servers than best of breed algorithms from the Web caching literature, e.g. Greedy Dual Size (Cao and Irani 1997). Figure 2: In this trial, weighted LFU (wLFU) provided higher value than unweighted frequency or recency based policies (uLFU and pLRU) Whereas weighted LFU successfully exploits server valuation information to deliver high value to system users, it is not likely to obtain this private ....

Irani, Sandy. 1997. Page replacement with multi-size pages and applications to Web caching. In Twenty-Ninth ACM Symposium on the Theory of Computing, El Paso, TX.

....policies is important. Whereas, models of processor memory hierarchies typically assume mandatory placement (e.g. Sleator and Tarjan on paging policies [34] in Web caching we need not require that a requested document always be cached (as in Irani s discussion of variable page size caching [23]) Optional placement Perfect LFU is optimal for infinite sequences of independent references from a fixed distribution, if document sizes are uniform. Limited empirical evidence, however, suggests that optionalplacement variants of LFU perform worse than their mandatory placement counterparts on ....

S. Irani, Page replacement with multi-size pages and applications to Web caching, 29th ACM STOC, May 1997, pp. 701--710.

....is propagated. Otherwise, the communication cost is zero. Using Definition 3. 9, we have the following definition for meta update propagation: PCC tot(t) X u2U(t) PCC(u; t) 6) Note that our use of the size of a file for calculating the communication cost is identical to the work of Irani [12]. One could have used the size of deltas [15] for calculating the communication cost. We don t do so because it is not clear to us how easy it would be to maintain multiple versions of the documents to account for the different states at the different search engines. The cost function (Cost) ....

S. Irani. Page replacement with multi-size pages and applications to web caching. In Proceedings of the ACM Symposium on Theory of Computing, pages 701--710, 1997.

....(CC) Consider an update u to a le f at time t. Then CC(u) at a later time t 1 is CC(u) size f (w f ) 1) provided that u is propagated before t 1 . Note that our use of the size of a le (or the size of the delta) for calculating the communication cost is identical to the work of Irani [Ira97] 4.3 The cost function Finally, we are ready to provide the cost function. De nition 4.7 Cost: Given an update u to a le f at time t, its cost at a later time t 1 is given by Cost(u) CC(u) OC(u) 2) using the contexts of De nitions 4.3 and 4.6) 5 A competitive algorithm The algorithm ....

S. Irani. Page replacement with multi-size pages and applications to web caching. In Proceedings of the ACM Symposium on Theory of Computing, pages 701-710, 1997.

....p, let size(p) be the size and cost(p) be the cost of p. The total size of the pages in fast memory may never exceed K. The goal is to serve a sequence of requests so that the total loading cost is as small as possible. Various cost models have been proposed in the literature. 1. The Bit Model [38]: For each page p, we have cost(p) size(p) The delay in bringing the page into fast memory depends only upon its size. 2. The Fault Model [38] For each page p, we have cost(p) 1 while the sizes can be arbitrary. 3. The Cost Model: For each page p, we have size(p) 1 while the costs can ....

....of requests so that the total loading cost is as small as possible. Various cost models have been proposed in the literature. 1. The Bit Model [38] For each page p, we have cost(p) size(p) The delay in bringing the page into fast memory depends only upon its size. 2. The Fault Model [38]: For each page p, we have cost(p) 1 while the sizes can be arbitrary. 3. The Cost Model: For each page p, we have size(p) 1 while the costs can be arbitrary. 4. The General Model: For each page p, both the cost and size can be arbitrary. In the Bit Model, and hence in the General Model, ....

S. Irani. Page replacement with multi-size pages and applications to Web caching. Proc. 29th Annual ACM Symp. on Theory of Computing, 701--710, 1997.

....all algorithms. We explore variants of LFU in which reference counts persist across evictions ( Perfect LFU in the terminology of Breslau et al. 6] and in which they are defined only for cached items ( incache LFU ) While some theoretical investigations consider the case of optional placement [13], we find empirically that it never confers a substantial advantage over mandatory placement and often incurs a severe performance penalty, possibly because it ensures that a large fraction of the many twice requested documents in our traces never result in cache hits. Therefore we consider only ....

Sandy Irani. Page replacement with multi-size pages and applications to Web caching. In 29th ACM STOC, pages 701--710, May 1997.

....recent applications related to the web involve situations in which pages can be of di#erent sizes and costs. This general caching problem seems more intricate than the uniform version. In particular, the offline case itself is NP hard. Only a few results exist for the general caching problem [8, 17]. This paper seeks to develop good o#ine page replacement policies for the general caching problem, with the hope that any insight gained here may lead to good online algorithms. Our first main result is that by using only a small amount of additional memory, say O(1) times the largest page size, ....

....one can obtain an O(log(M C) approximation where M and C denote the cache size and the largest page fault cost, respectively. Our results use a new rounding technique for linear programs which may be of independent interest. We also present a randomized online algorithm for the Bit Model [8] which achieves a competitive ratio of O(ln(1 1 c) while using M(1 c) memory. 1 Introduction When a sequence of memory objects ( pages ) are to be retrieved from a slow or distant memory, one often uses a cache i.e. a fast memory of some small size, say M to retain some ....

[Article contains additional citation context not shown here]

S. Irani. Page replacement with multi-size pages and applications to Web caching. Proc. 29th Annual ACM Symp. on Theory of Computing, 701--710, 1997.

....not get such notifications. Our goal is to minimize the total activation cost incurred while servicing the sequence oe. We consider both on line and off line scenarios as well as distributed and centralized ones. 2. 1 Varying establishment costs and buffer sizes As in the case of a single cache [10, 21, 22], the connection caching model can be generalized by allowing varying sizes and fetching costs. In the TCP context, sizes may correspond to socket buffers allocations, but use of uniform sizes seems most reasonable. Establishment costs may capture the user perceived latency caused by ....

S. Irani. Page replacement with multi-size pages and applications to web caching. In Proc. 29th Annual ACM Symposium on Theory of Computing. ACM, 1997.

....environment exhibit different characteristics than in traditional operating systems paging. One wellrecognized difference is the variability in sizes and fetching costs of different resources (pages) and indeed, replacement policies that incorporate these parameters were suggested and evaluated [7, 13, 21, 20]. As is the case in traditional paging, individual requests remain hard to predict. We focus on two separate predictable aspects of the traffic in the web environment. The first is the usage levels experienced by large proxy and (typically) web servers. The second is distinct per page ....

....Future requests for new pages, however, are not provided apriori. When page sizes and fetching costs are uniform, this information suffices to do optimally, by simply evicting the page to be requested furthest in the future [4] When fetching costs vary, however, this information is insufficient [13]. Intuitively, with uniform costs there is a total order on the value of all cached pages (according to their next request time) With varying costs, the relative value of cached pages depends on future requests for pages not yet seen. As a simple example, suppose that the replacement algorithm ....

[Article contains additional citation context not shown here]

S. Irani. Page replacement with multi-size pages and applications to web caching. In Proc. 29th Annual ACM Symposium on Theory of Computing. ACM, 1997.

....that may occur when requests and their responses are routed within the network. We also remark that cost models have been adopted in uniprocessor caching systems to model scenarios in which the costs incurred in the retrieval of objects on cache misses may vary from one object to another [9, 17, 28]. 3 2 Preliminaries In this section, we formally define the placement problem and its restriction to hierarchical networks. 2.1 The placement problem. We adopt a standard model for arbitrary networks (see, e.g. 2, 13, 15, 27] in which we represent a network by a set M of machines and a ....

S. Irani. Page replacement with multi-size pages and applications to Web caching. In Proceedings of the 29th Annual ACM Symposium on the Theory of Computing, pages 701--710, May 1997.

....that may occur when requests and their responses are routed within the network. We also remark that cost models have been adopted in uniprocessor caching systems to model scenarios in which the costs incurred in the retrieval of objects on cache misses may vary from one object to another [10, 19, 33]. With regard to uniprocessor caching schemes, recent research has addressed the challenge of designing cache replacement policies that take into account the differing costs incurred in the retrieval of objects on cache misses. This has led to studies formulating generalizations of the ....

....addressed the challenge of designing cache replacement policies that take into account the differing costs incurred in the retrieval of objects on cache misses. This has led to studies formulating generalizations of the traditional uniprocessor caching problems that account for the differing costs [10, 19, 33]. In a recent experimental study [21] Korupolu and Dahlin evaluate the practical performance of several placement and replacement algorithms for cooperative caching. Their simulation experiments demonstrate that, in practice, both our greedy placement algorithm as well as our amortizing ....

S. Irani. Page replacement with multi-size pages and applications to Web caching. In Proceedings of the 29th Annual ACM Symposium on Theory of Computing, pages 701--710, May 1997.

....related to the performance of computer systems are online. Examples include: Deciding which variables to keep in the cache (fast memory) during the execution of a program so as to maximize cache utilization [56, 9, 21, 40, 30] Deciding which web pages to keep in the cache of a web browser [28, 59]; Deciding how to distribute data on a network so as to minimize network tra#c or response time [34, 58, 3, 13] 5 . Deciding how to schedule a job when future jobs are unknown so as to optimize a given criteria [1, 33, 5] In addition, many problems from other areas, such as ....

....fundamental and practical online problems in computer science. The advent of the world wide web has brought about a new wave of interest in such problems, as caching strategies have the potential to greatly decrease web page access times. Some initial research on online web caching has been done [28, 59], however, there are great number of problems left to be explored. Scheduling involves the assignment of tasks to resources. Scheduling problems are ubiquitous. The tasks could be the running of a computer program, the manufacture of a car part, the playing of a baseball game, et cetera. The ....

Irani, S. Page replacement with multi-size pages and applications to web caching. In Proceedings of the 29th ACM Symposium on the Theory of Computing (1997), pp. 701--710.

....we state an alternative proof to the performance guarantee of greedy dual size. Our proof provides additional insights into the algorithm. Our LP formulation has other applications. For example, along with randomized rounding [4] it can be used to obtain an approximate solution to the NP complete [3] offline problem, when page sizes are small with respect to the cache size. 2 Preliminaries Let s(p) be the size of a page p and let f(p) be the cost of fetching p at the time of its next request (the cost of a cache miss resulting from evicting p) In particular, if p is never requested again, ....

....with respect to the cache size. 2 Preliminaries Let s(p) be the size of a page p and let f(p) be the cost of fetching p at the time of its next request (the cost of a cache miss resulting from evicting p) In particular, if p is never requested again, we assume that f(p) 0. Similar to Irani [3], we charge the algorithm by the respective fetching costs upon each decision to evict or not to cache a page. This cost measure differs by an additive constant 1 (incured by all algorithms) from charging for the fetching cost upon each miss. Note that competitive ratio results that hold for the ....

[Article contains additional citation context not shown here]

S. Irani. Page replacement with multi-size pages and applications to web caching. In Proc. 29th Annual ACM Symposium on Theory of Computing. ACM, 1997.

....nodes are allocated in an N long array indexed by document ID, so locating a node requires O(1) time. All of the other operations require O(log N) time, for a total of O(M log N) time to process the entire input sequence. always be cached (as in Irani s discussion of variable page size caching [23]) Optional placement Perfect LFU is optimal for infinite sequences of independent references from a fixed distribution, if document sizes are uniform. Limited empirical evidence, however, suggests that optionalplacement variants of LFU perform worse than their mandatory placement counterparts on ....

Sandy Irani. Page replacement with multi-size pages and applications to Web caching. In 29th ACM STOC, pages 701--710, May 1997.

....strategies such as LFU. On the other hand, the temporal locality of reference in Web request streams suggest the use of short term residency information (e.g. time since last access) in replacement strategies for caching protocols. LRU cache replacement strategies and its generalization [12, 24] leverage on this property. The relationship and distinction between popularity and temporal locality properties in Web access patterns is often blured. This is partially the result of the causal relationship between these two properties highly popular documents tend to be referenced frequently, ....

Sandy Irani. Page replacement with multi-size pages and applications to Web caching. In Proceedings of the 12th annual ACM symposium on Theory of computing, 1997.

....of basic cache replacement algorithms. Hybrid policies: Several studies have generalized LRU to make it more sensitive to the variability in object size and retrieval delays. The GreedyDual algorithm [23] was proposed to deal with variable cost uniform size page caching problem. Cao and Irani [9, 15] generalized the GreedyDual algorithm to deal with variable size Web objects. The resulting algorithm, GreedyDual Size (GDS) enables a cache replacement strategy to be sensitive to both the variability in Web object sizes and retrieval costs (miss penalty) The GDS implementation described in [9] ....

Sandy Irani. Page replacement with multi-size pages and applications to Web caching. In Proceedings of the 12th annual ACM symposium on Theory of computing, May, 1997.

....A number of recent studies have examined the question of what to store in caches. There are several studies and prototypes (e.g. 3, 2, 17, 21] that employ purely local replacement strategies such as LRU or greedy dual at each cache. The greedy dual local replacement algorithm was evaluated in [2, 11, 23], but for single stand alone caches only. Here we study their performance in a cooperative caching scenario. The placement and replacement algorithms for local area networks were studied by Leff et al. 14] Dahlin et al. 5] and Feeley et al. 7] However the scenario of wide area networks is ....

S. Irani. Page replacement with multi-size pages and applications to Web caching. In Proceedings of the 29th Annual ACM Symposium on Theory of Computing, pages 701--710, May 1997.

....Web caching is the temporary local storage of WWW pages by a browser for later retrieval. From the user s point of view, the primary benefit of caching is reduced latency, as the time to access locally stored objects is minimal. We adopt the following standard general model of web caching [1, 5, 8, 14]: Web Caching Problem Statement: The browser is given an online sequence S of page requests, where each page p i 2 S has a size s(i) say, in bytes) and an access time t(i) that is required if p i is not cached. If the requested page p i is not in the cache (this is called a cache miss) then the ....

....for Web Caching on depth first tree traversal sequences S of T , the competitive ratio compares A(S) against the optimal offline cost. We will show that the optimal offline cost may be much higher than t(T ) There are three special cases of the caching models that have been studied previously [1, 8]. In the bit model the access time is assumed to equal the size of the page. This model would be appropriate if the pages are large and the delay in the network is small. In the cost model the size of each page is one, while the access times are allowed to be arbitrary. This is an appropriate ....

[Article contains additional citation context not shown here]

S. Irani, "Page replacement with multi-size pages and applications to web caching", ACM Symposium on Theory of Computing, 701--710, 1997.

....A number of recent studies have examined the question of what to store in caches. There are several studies and prototypes (e.g. 3, 2, 17, 21] that employ purely local replacement strategies such as LRU or GreedyDual at each cache. The GreedyDual local replacement algorithm was evaluated in [2, 11, 23], but for single stand alone caches only. Here we study their performance in a cooperative caching scenario. The placement and replacement algorithms for local area networks were studied by Leff et al. 14] Dahlin et al. 5] and Feeley et al. 7] However the scenario of wide area networks is ....

S. Irani. Page replacement with multi-size pages and applications to web caching. In Proceedings of the 29th Annual ACM Symposium on the Theory of Computing, pages 701-- 710, May 1997.

.... and the time for last access as the secondary key (e.g. the HyperG) 35] 5) the logarithm of object sizes as the primary key and the time for last access as the secondary key (LRU MIN) 36] 6) time for last access per object group where the logarithm of object sizes is used to group objects [68], and (7) the estimate of the average page loading delay and retrieval time [10, 126] Since most of the data accessed on the web today contains text and static images, the above described algorithms seem adequate. Recent studies, however, predict a shift towards continuous media data in the ....

S. Irani. Page Replacement with Multi-Size Pages and Applications to Web Caching. In Proceedings of the Twenty-ninth ACM Symposium on Theory of Computing, 1997.

....algorithms. We explore variants of LFU in which reference counts persist across evictions ( Perfect LFU in the terminology of Breslau et al. 17] and in which they are defined only for cached items ( in cache LFU ) While some theoretical investigations consider the case of optional placement [19], we find empirically that it never confers a substantial advantage over mandatory placement and often incurs a severe performance penalty. 2 Lee et al. 18] define a different continuum between LRU and LFU for the unweighted case (Wu = 1 for all u) Bahn et al. have very recently generalized ....

Sandy Irani, "Page replacement with multi-size pages and applications to Web caching," in 29th ACM STOC, May 1997, pp. 701--710.

....Fig. 5. Byte HR at cache sizes 1MB 8GB for LRU and four LFU variants, August 1998 NLANR SV trace. LFU in the terminology of Breslau et al. 17] and in which they are defined only for cached items ( in cache LFU ) While some theoretical investigations consider the case of optional placement [19], we find empirically that it never confers a substantial advantage over mandatory placement and often incurs a severe performance penalty. Therefore we consider only mandatory placement variants of LFU. From a large spectrum of algorithms with different prediction characteristics, we used our ....

Sandy Irani, "Page replacement with multi-size pages and applications to Web caching," in 29th ACM STOC, May 1997, pp. 701--710.

....basic cache replacement algorithms. Hybrid Policies: Several studies have generalized LRU to make it more sensitive to the variability in object size and retrieval delays. The GreedyDual algorithm [24] was proposed to deal with variable cost (but uniform size) page caching problem. Cao and Irani [9, 15] generalized the 1 Previous studies [7] indicate that the independent reference model [10] explains well the distribution properties of Web access, supporting the use of of frequency based policies. 2 This is in contrast to indirectly inferring popularity through locality of reference or ....

Sandy Irani. Page replacement with multi-size pages and applications to Web caching. In Proceedings of the 12th annual ACM symposium on Theory of computing, 1997.

....extensively in the context of processor architecture and file systems, the Web introduces more complicated challenges, since resources vary substantially in their sizes, fetching costs, and access patterns. Indeed, new replacement policies have been developed to incorporate these parameters [1, 2, 3, 4]. Although the Web exhibits high variability between the access patterns of different resources, individual resources have more regular acccess patterns. The most important factor for a good replacement policy remains predicting the next request time of a resource which depends on the ability to ....

S. Irani, "Page replacement with multi-size pages and applications to web caching," in Proc. 29th Annual ACM Symposium on Theory of Computing, 1997.

....recent applications related to the web involve situations in which pages can be of different sizes and costs. This general caching problem seems more intricate than the uniform version. In particular, the offline case itself is NP hard. Only a few results exist for the general caching problem [8, 17]. This paper seeks to develop good offline page replacement policies for the general caching problem, with the hope that any insight gained here may lead to good online algorithms. Our first main result is that by using only a small amount of additional memory, say O(1) times the largest page ....

....one can obtain an O(log(M C) approximation where M and C denote the cache size and the largest page fault cost, respectively. Our results use a new rounding technique for linear programs which may be of independent interest. We also present a randomized online algorithm for the Bit Model [8] which achieves a competitive ratio of O(ln(1 1=c) while using M(1 c) memory. 1 Introduction When a sequence of memory objects ( pages ) are to be retrieved from a slow or distant memory, one often uses a cache i.e. a fast memory of some small size, say M to retain some ....

[Article contains additional citation context not shown here]

S. Irani. Page replacement with multi-size pages and applications to Web caching. Proc. 29th Annual ACM Symp. on Theory of Computing, 701--710, 1997.

....and so adds little to server cache communication overheads. Note that we must explicitly account for URLs larger than the cache, and that in our algorithm a URL is always guaranteed to be in cache after it is requested. Many authors fail to specify whether placement is mandatory or optional; Irani [14] and Cao Irani [6] are among the rare exceptions. time of last access, and LFU sorts on number of references. We define server weighted LFU cache replacement (swLFU) as follows: For every cached URL u, let N u be the number of references to u since it entered the cache 1 and let weight W u ....

Sandy Irani. Page replacement with multi-size pages and applications to Web caching. In 29th ACM Symposium on the Theory of Computing, pages 701--710, May 1997.

.... (see comment below) Irani considered two special cases of file caching: when the costs are either all equal (the goal is to minimize the number of retrievals) and when each cost equals the file size (the goal is to minimize the total number of bytes retrieved) For these two cases, Irani [7] gave O(log 2 k) competitive randomized on line algorithms. Comment: the importance of sizes and costs. File caching is important for world wide web applications. For instance, in browsers and proxy servers remote files are cached locally to avoid remote retrieval. In web servers, disk files ....

....the importance of sizes and costs. File caching is important for world wide web applications. For instance, in browsers and proxy servers remote files are cached locally to avoid remote retrieval. In web servers, disk files are cached in fast memory to speed response time. As Irani points out (see [7] and references therein) file size is an important consideration; caching policies adapted from memory management applications that don t take size into account do not work well in practice. Allowing arbitrary costs is likely to be important as well. In many cases, the cost (e.g. latency, total ....

Sandy Irani. Page replacement with multi-size pages and applications to Web caching. In ACM [1], pages 701--710.

....extensively in the context of processor architecture and file systems, the Web introduces more complicated challenges, since resources vary substantially in their sizes, fetching costs, and access patterns. Indeed, new replacement policies have been developed to incorporate these parameters [1, 2, 3, 4]. Although the Web exhibits high variability between the 1 Revision of an ESA 98 paper access patterns of different resources, individual resources have more regular acccess patterns. The most important factor for a good replacement policy remains predicting the next request time of a ....

S. Irani, "Page replacement with multi-size pages and applications to web caching," in Proc. 29th Annual ACM Symposium on Theory of Computing, ACM, 1997.

....in the future will yield the optimal performance [Bel66] In the variable size case, no such offline algorithm is known. In fact, it is known that determining the optimal performance is NP hard [Ho97] although there is an algorithm which can approximate the optimal to within a logarithmic factor [Ir97]. The approximation factor is logarithmic in the maximum number of bytes that can fit in the cache, which we will call k. For the cost consideration, there have been several algorithms developed for the uniform size variablecost paging problem. GreedyDual [You91b] is actually a range of ....

S. Irani. Page replacement with multi-size pages and applications to web caching. In the Proceedings for the 29th Symposium on the Theory of Computing, 1997, pages 701-710.

....k off 1) competitive [You91b] where k on and k off are the sizes of the online and offline caches respectively. This class of algorithms include BALANCE as well as a generalization of LRU. 6. 2 Multi Size Pages The paging problem in which pages have varying sizes has been examined by Irani in [Ira97] This problem is motivated by cache management for World Wide Web documents where documents held in the cache can vary dramatically in size, depending largely on the type of information they contain (e.g. text, video, audio) Again, since this is a generalization of paging, the lower bound of ....

Sandy Irani. Page replacement with multi-size pages and applications to web caching. In Proc. 29rd ACM Symposium on Theory of Computing, pages 701--710, 1997.

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S. Irani, "Page Replacement with Multi-Size Pages and Applications to Web Caching," Proc. 29th Ann. ACM Symp. Theory of Computing (STOC '97), pp. 701-710, 1997.

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S. Irani. Page replacement with multi-size pages and applications to web caching. In 29th ACM Symposium on Theory of Computing, pages 701--710, May 1997.

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S. Irani. Page replacement with multi-size pages and applications to web caching. In Proc. 29th Annual ACM Symposium on Theory of Computing. ACM, 1997.

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S. Irani. "Page Replacement with Multi-Size Pages and Applications to Web Caching". Algorithmica, 33(3):384--409, 2002.

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S. Irani. Page replacement with multi-size pages and applications to web caching, Proc. 29th ACM Symposium on Theory of Computing pp 701-710, 1997.

No context found.

S. Irani. Page replacement with multi-size pages and applications to web caching. In 29th ACM Symposium on Theory of Computing, pages 701--710, May 1997.

No context found.

S. Irani. Page replacement with multi-size pages and applications to Web caching. In Proceedings of the 29th Annual ACM Symposium on Theory of Computing, pages 701--710, May 1997.

No context found.

S. Irani. Page replacement with multi-size pages and applications to web caching. In 29th ACM Symposium on Theory of Computing, pages 701--710, May 1997.

No context found.

S. Irani. Page replacement with multi-size pages and applications to web caching. In Proc. 29th Annual ACM Symposium on Theory of Computing. ACM, 1997.

No context found.

S. Irani. "Page Replacement with Multi-Size Pages and Applications to Web Caching". Algorithmica, 33(3):384--409, 2002.

No context found.

S. Irani. Page replacement with multi-size pages and applications to Web caching. Algorithmica, 33(1):384--409, 2002.

No context found.

S. Irani. Page replacement with multi-size pages and applications to web caching. In Proceedings of the Annual ACM Symposium on the Theorey of Computing, March 1997.

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