forked from luck/tmp_suning_uos_patched
bb4aa39676
In anon_vma_clone() we traverse the vma->anon_vma_chain of the source vma, locking the anon_vma for each entry. But they are all going to have the same root entry, which means that we're locking and unlocking the same lock over and over again. Which is expensive in locked operations, but can get _really_ expensive when that root entry sees any kind of lock contention. In fact, Tim Chen reports a big performance regression due to this: when we switched to use a mutex instead of a spinlock, the contention case gets much worse. So to alleviate this all, this commit creates a small helper function (lock_anon_vma_root()) that can be used to take the lock just once rather than taking and releasing it over and over again. We still have the same "take the lock and release" it behavior in the exit path (in unlink_anon_vmas()), but that one is a bit harder to fix since we're actually freeing the anon_vma entries as we go, and that will touch the lock too. Reported-and-tested-by: Tim Chen <tim.c.chen@linux.intel.com> Tested-by: Hugh Dickins <hughd@google.com> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Andi Kleen <ak@linux.intel.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> |
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| .. | ||
| backing-dev.c | ||
| bootmem.c | ||
| bounce.c | ||
| cleancache.c | ||
| compaction.c | ||
| debug-pagealloc.c | ||
| dmapool.c | ||
| fadvise.c | ||
| failslab.c | ||
| filemap_xip.c | ||
| filemap.c | ||
| fremap.c | ||
| highmem.c | ||
| huge_memory.c | ||
| hugetlb.c | ||
| hwpoison-inject.c | ||
| init-mm.c | ||
| internal.h | ||
| Kconfig | ||
| Kconfig.debug | ||
| kmemcheck.c | ||
| kmemleak-test.c | ||
| kmemleak.c | ||
| ksm.c | ||
| maccess.c | ||
| madvise.c | ||
| Makefile | ||
| memblock.c | ||
| memcontrol.c | ||
| memory_hotplug.c | ||
| memory-failure.c | ||
| memory.c | ||
| mempolicy.c | ||
| mempool.c | ||
| migrate.c | ||
| mincore.c | ||
| mlock.c | ||
| mm_init.c | ||
| mmap.c | ||
| mmu_context.c | ||
| mmu_notifier.c | ||
| mmzone.c | ||
| mprotect.c | ||
| mremap.c | ||
| msync.c | ||
| nobootmem.c | ||
| nommu.c | ||
| oom_kill.c | ||
| page_alloc.c | ||
| page_cgroup.c | ||
| page_io.c | ||
| page_isolation.c | ||
| page-writeback.c | ||
| pagewalk.c | ||
| percpu-km.c | ||
| percpu-vm.c | ||
| percpu.c | ||
| pgtable-generic.c | ||
| prio_tree.c | ||
| quicklist.c | ||
| readahead.c | ||
| rmap.c | ||
| shmem.c | ||
| slab.c | ||
| slob.c | ||
| slub.c | ||
| sparse-vmemmap.c | ||
| sparse.c | ||
| swap_state.c | ||
| swap.c | ||
| swapfile.c | ||
| thrash.c | ||
| truncate.c | ||
| util.c | ||
| vmalloc.c | ||
| vmscan.c | ||
| vmstat.c | ||