[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [Xen-devel] [PATCH v3 0/9] Memory scrubbing from idle loop
When a domain is destroyed the hypervisor must scrub domain's pages before giving them to another guest in order to prevent leaking the deceased guest's data. Currently this is done during guest's destruction, possibly causing very lengthy cleanup process. This series adds support for scrubbing released pages from idle loop, making guest destruction significantly faster. For example, destroying a 1TB guest can now be completed in 40+ seconds as opposed to about 9 minutes using existing scrubbing algorithm. Briefly, the new algorithm places dirty pages at the end of heap's page list for each node/zone/order to avoid having to scan full list while searching for dirty pages. One processor form each node checks whether the node has any dirty pages and, if such pages are found, scrubs them. Scrubbing itself happens without holding heap lock so other users may access heap in the meantime. If while idle loop is scrubbing a particular chunk of pages this chunk is requested by the heap allocator, scrubbing is immediately stopped. On the allocation side, alloc_heap_pages() first tries to satisfy allocation request using only clean pages. If this is not possible, the search is repeated and dirty pages are scrubbed by the allocator. This series is somewhat based on earlier work by Bob Liu. V1: * Only set PGC_need_scrub bit for the buddy head, thus making it unnecessary to scan whole buddy * Fix spin_lock_cb() * Scrub CPU-less nodes * ARM support. Note that I have not been able to test this, only built the binary * Added scrub test patch (last one). Not sure whether it should be considered for committing but I have been running with it. V2: * merge_chunks() returns new buddy head * scrub_free_pages() returns softirq pending status in addition to (factored out) status of unscrubbed memory * spin_lock uses inlined spin_lock_cb() * scrub debugging code checks whole page, not just the first word. V3: * Keep dirty bit per page * Simplify merge_chunks() (now merge_and_free_buddy()) * When scrubbing memmory-only nodes try to find the closest node. Deferred: * Per-node heap locks. In addition to (presumably) improving performance in general, once they are available we can parallelize scrubbing further by allowing more than one core per node to do idle loop scrubbing. * AVX-based scrubbing * Use idle loop scrubbing during boot. Boris Ostrovsky (9): mm: Separate free page chunk merging into its own routine mm: Place unscrubbed pages at the end of pagelist mm: Scrub pages in alloc_heap_pages() if needed mm: Scrub memory from idle loop mm: Do not discard already-scrubbed pages if softirqs are pending spinlock: Introduce spin_lock_cb() mm: Keep pages available for allocation while scrubbing mm: Print number of unscrubbed pages in 'H' debug handler mm: Make sure pages are scrubbed xen/Kconfig.debug | 7 + xen/arch/arm/domain.c | 13 +- xen/arch/x86/domain.c | 3 +- xen/common/page_alloc.c | 529 ++++++++++++++++++++++++++++++++++++++------ xen/common/spinlock.c | 9 +- xen/include/asm-arm/mm.h | 10 + xen/include/asm-x86/mm.h | 10 + xen/include/xen/mm.h | 1 + xen/include/xen/spinlock.h | 8 + 9 files changed, 513 insertions(+), 77 deletions(-) _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx https://lists.xen.org/xen-devel
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