Kevin Elphinstone, Stephen Russell, Gernot Heiser, and Jochen Liedtke, Supporting Persistent Object Systems in a Single Address Space, In 7th International Workshop on Persistent Object Systems (POS7), Cape May, NJ, USA, May 1996.  Home/Search   Document Details and Download   Summary   Related Articles   Check

....to implement its own persistence policy by exposing all in kernel meta data to the application. The application has to ensure persistence itself by storing the data. As such, no specific persistence model is enforced. There are also persistent single address space operating systems like Mungi [21], Opal and many other. In these systems protection and security is not implemented by address space boundaries but by capabilities or strong language environments. Orthogonal persistence in these systems is just the extension of the systems paging mechanism to store the main memory on a storage ....

Kevin Elphinstone, Stephen Russell, Gernot Heiser, and Jochen Liedtke, Supporting Persistent Object Systems in a Single Address Space, In 7th International Workshop on Persistent Object Systems (POS7), Cape May, NJ, USA, May 1996.

....of the single address space. This is achieved by omitting from the model anything which would introduce any other forms of name spaces. For example, there is no I O model; clients which require explicit control over I O, such as database systems, can achieve this via virtual memory operations [ERHL96] as devices are memory mapped. The control registers of devices, as well as the contents of disk drives and physical memory, are mapped into the virtual memory. The device driver is given the capability to read and write the appropriate memory regions, and users can then safely request ....

....port driver currently only exports read, write and initialise operations, with the users only having access to the read and write operations. 5. 5 User level page fault handlers User level pagers (ULPs) are essential for efficiently supporting databases and implementing persistence in Mungi [ERHL96] A ULP is a PDX procedure which is invoked by the kernel when a page fault occurs on an object for which that ULP had been registered. ULP invocation uses an zero npd parameter. Hence, the ULP runs within just the protection domain which was registered for it. As the ULP has no access to either ....

Kevin Elphinstone, Stephen Russell, Gernot Heiser, and Jochen Liedtke. Supporting persistent object systems in a single address space. In Proceedings of the 7th International Workshop on Persistent Object Systems, pages 111--119, Cape May, NJ, USA, May 1996. Morgan Kaufmann.

....without redesign and reimplementation of the programming language if one is prepared instead to layer support for persistence into the operating system. Several experimental projects have taken this approach: support for persistence is targeted explicitly in Grasshopper [29, 71] and Mungi [34, 37], but the rudiments are there in other experimental operating systems such as Opal [24, 25] among others. Our interest here focuses on efficient support for orthogonal persistence on stock operating systems. 4 Mostly copying garbage collection Mostly copying garbage collection [12, 13] is a ....

ELPHINSTONE,K.,RUSSELL,S.,HEISER,G.,AND LIEDTKE,J. Supporting persistent object systems in a single address space. In Connor and Nettles [27], pp. 111--119.

....Arias is persistent which means that regions of shared memory survives the termination of the process that allocated the memory. The advantages of SASA s for building distributed object support systems has been proven by existing Single Address Space Operating Systems (SASOS) like Opal [3] Mungi [4]. or Angel [8] Two of the major advantages are naming and management of persistence. Virtual addresses can be used as global object identi ers. There is no need to convert objects between an internal representation and an external le format (typically a byte stream) when objects are loaded from ....

K. Elphinstone, S. Russell, G. Heiser, and J. Liedtke. Supporting persistent object systems in a single address space. In 7th Conference on Persistent Object Systems (POS), Cape May, NJ, USA, May 1996.

....the single address space concept seriously, by keeping out of the model anything which would introduce other forms of address space. For example, there is no disk model; clients, such as database systems, which require explicit control over I O, can achieve this via virtual memory operations [ERHL96] Similarly, other devices are mapped into VM. The device driver is given capability to the appropriate memory region. Users can then safely perform operations on the device by invoking the driver via a PDX call. 5.2. Services Object oriented systems traditionally implement services using ....

....domains, by specifying a reduced protection domain in the PDX call, if they do not trust the called PDX library function . 5.3. User level page fault handlers User level page fault handlers (ULPs) are essential for efficiently supporting databases and implementing persistence in Mungi [ERHL96] A ULP is a PDX procedure which is invoked by the kernel when a page fault occurs on an object for which that ULP had been registered. ULP invocation uses an empty clist parameter, hence the ULP runs just within the protection domain which was registered for it. As the ULP has no access to ....

Kevin Elphinstone, Stephen Russell, Gernot Heiser, and Jochen Liedtke. Supporting persistent object systems in a single address space. In Proceedings of the 7th International Workshop on Persistent Object Systems, Cape May, NJ, USA, May 1996. To be published.

....object. As there is no I O model in the system, a pager cannot use I O operations to handle a residency fault. Instead, the pager uses another virtual memory object to page to. To support such forwarding of page faults, Mungi provides mapping operations between different regions of virtual memory [30]. Pages belonging to an object O 1 may be mapped to another object O 2 , which causes O 2 s pager to be 13 invoked when necessary. Page faults may be forwarded several times until they reach the default pager (and thus physical memory) Figure 3 shows how a page fault is handled by a user level ....

....as virtual caches would not require physical tags. The addition of virtual memory mapping operations has made it possible to incorporate into the single address space model user level pagers and I O, and leave, for example, the implementation of stability and fault tolerance to the user level [30]. This allowed us to build a pure SASOS, where virtual memory is the only communication medium between processes. Since we had to implement the microkernel as well as the higher layers of the system, the question naturally arises whether it was a good idea to base the implementation of Mungi on ....

K. Elphinstone, S. Russell, G. Heiser, and J. Liedtke. Supporting persistent object systems in a single address space. In Proceedings of the 7th International Workshop on Persistent Object Systems, pages 111--119, Cape May, NJ, USA, May 1996. Morgan Kaufmann.

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