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1418 results about "Virtual address space" patented technology

In computing, a virtual address space (VAS) or address space is the set of ranges of virtual addresses that an operating system makes available to a process. The range of virtual addresses usually starts at a low address and can extend to the highest address allowed by the computer's instruction set architecture and supported by the operating system's pointer size implementation, which can be 4 bytes for 32-bit or 8 bytes for 64-bit OS versions. This provides several benefits, one of which is security through process isolation assuming each process is given a separate address space.

Efficient write-watch mechanism useful for garbage collection in a computer system

An efficient write-watch mechanism and process. A bitmap is associated with the virtual address descriptor (VAD) for a process, one bit for each virtual page address allocated to a process having write-watch enabled. As part of the write-watch mechanism, if a virtual address is trimmed to disk and that virtual address page is marked as modified, then the corresponding bit in the VAD is set for that virtual address page. In response to an API call (e.g., from a garbage collection mechanism) seeking to know which virtual addresses in a process have been modified since last checked, the memory manager walks the bitmap in the relevant VAD for the specified virtual address range for the requested process. If a bit is set, then the page corresponding to that bit is known to have been modified since last asked. If specified by the API, the bit is cleared in the VAD bitmap so that it will reflect the state since this time of asking. If the bit is not set, to determine if the page was modified, the page table entry (PTE) is checked for that page, and if the PTE indicates the page was modified, the page is known to be modified, otherwise that page is known to be unmodified since the last call. One enhancement uses page directory tables to locate a series of trimmed pages, sometimes avoiding the need to access the PTE.
Owner:MICROSOFT TECH LICENSING LLC

Providing global translations with address space numbers

A processor provides a register for storing an address space number (ASN). Operating system software may assign different ASNs to different processes. The processor may include a TLB to cache translations, and the TLB may record the ASN from the ASN register in a TLB entry being loaded. Thus, translations may be associated with processes through the ASNs. Generally, a TLB hit will be detected in an entry if the virtual address to be translated matches the virtual address tag and the ASN matches the ASN stored in the register. Additionally, the processor may use an indication from the translation table entries to indicate whether or not a translation is global. If a translation is global, then the ASN comparison is not included in detecting a hit in the TLB. Thus, translations which are used by more than one process may not occupy multiple TLB entries. Instead, a hit may be detected on the TLB entry storing the global translation even though the recorded ASN may not match the current ASN. In one embodiment, if ASNs are disabled, the TLB may be flushed on context switches. However, the indication from the translation table entries used to indicate that the translation is global may be used (when ASNs are disabled) by the TLB to selectively invalidate non-global translations on a context switch while not invalidating global translations.
Owner:GLOBALFOUNDRIES US INC

Garbage collector for a virtual heap

A method and system for performing generational garbage collection on a virtual heap in a virtual machine is provided. The garbage collection method is suited for use with small consumer and appliance devices that have a small amount of memory and may be using flash devices as persistent storage. The garbage collection method may provide good performance where only a portion of the virtual heap may be cached in the physical heap. The virtual heap may use a single address space for both objects in the store and the in-memory heap. In one embodiment, a single garbage collector is run on the virtual heap address space. The garbage collection method may remove non-referenced objects from the virtual heap. The garbage collection method may also include a compaction phase to reduce or eliminate fragmentation, and to improve locality of objects within the virtual heap. In one embodiment, the garbage collector for the virtual heap may be implemented as a generational garbage collector using working sets in the virtual heap, where each generation is confined to a working set of the heap. The generational garbage collector may allow the flushing of changes after each garbage collection cycle for each working set region. Heap regions with different flushing policies may be used. An object nursery region without flushing where objects are initially created may be used. When a garbage collection cycle is run, objects truly referenced in the object nursery may be copied back into heap regions to be flushed, while short-lived objects no longer referenced may be deleted without flushing.
Owner:ORACLE INT CORP +1
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