Hello, This series is a continuation of the conversion of the i_mmap_mutex to rwsem, following what we have for the anon memory counterpart. With Hugh's feedback from the first iteration (sorry about leaving this fall behind for so long, but I've just finally had time to re-look at this -- see https://lkml.org/lkml/2014/5/22/797), several additional opportunities for sharing the lock are proposed. Ultimately, the most obvious paths that require exclusive ownership of the lock is when we modify the VMA interval tree, via vma_interval_tree_insert() and vma_interval_tree_remove() families. Cases such as unmapping, where the ptes content is changed but the tree remains untouched should make it safe to share the i_mmap_rwsem. As such, the code of course is straightforward, however the devil is very much in the details. While its been tested on a number of workloads without anything exploding, I would not be surprised if there are some less documented/known assumptions about the lock that could suffer from these changes. Or maybe I'm just missing something, but either way I believe its at the point where it could use more eyes and hopefully some time in linux-next. Because the lock type conversion is the heart of this patchset, its worth noting a few comparisons between mutex vs rwsem (xadd): (i) Same size, no extra footprint. (ii) Both have CONFIG_XXX_SPIN_ON_OWNER capabilities for exclusive lock ownership. (iii) Both can be slightly unfair wrt exclusive ownership, with writer lock stealing properties, not necessarily respecting FIFO order for granting the lock when contended. (iv) Mutexes can be slightly faster than rwsems when the lock is non-contended. (v) Both suck at performance for debug (slowpaths), which shouldn't matter anyway. Sharing the lock is obviously beneficial, and sem writer ownership is close enough to mutexes. The biggest winner of these changes is migration. As for concrete numbers, the following performance results are for a 4-socket 60-core IvyBridge-EX with 130Gb of RAM. Both alltests and disk (xfs+ramdisk) workloads of aim7 suite do quite well with this set, with a steady ~60% throughput (jpm) increase for alltests and up to ~30% for disk for high amounts of concurrency. Lower counts of workload users (< 100) does not show much difference at all, so at least no regressions. 3.18-rc1 3.18-rc1-i_mmap_rwsem alltests-100 17918.72 ( 0.00%) 28417.97 ( 58.59%) alltests-200 16529.39 ( 0.00%) 26807.92 ( 62.18%) alltests-300 16591.17 ( 0.00%) 26878.08 ( 62.00%) alltests-400 16490.37 ( 0.00%) 26664.63 ( 61.70%) alltests-500 16593.17 ( 0.00%) 26433.72 ( 59.30%) alltests-600 16508.56 ( 0.00%) 26409.20 ( 59.97%) alltests-700 16508.19 ( 0.00%) 26298.58 ( 59.31%) alltests-800 16437.58 ( 0.00%) 26433.02 ( 60.81%) alltests-900 16418.35 ( 0.00%) 26241.61 ( 59.83%) alltests-1000 16369.00 ( 0.00%) 26195.76 ( 60.03%) alltests-1100 16330.11 ( 0.00%) 26133.46 ( 60.03%) alltests-1200 16341.30 ( 0.00%) 26084.03 ( 59.62%) alltests-1300 16304.75 ( 0.00%) 26024.74 ( 59.61%) alltests-1400 16231.08 ( 0.00%) 25952.35 ( 59.89%) alltests-1500 16168.06 ( 0.00%) 25850.58 ( 59.89%) alltests-1600 16142.56 ( 0.00%) 25767.42 ( 59.62%) alltests-1700 16118.91 ( 0.00%) 25689.58 ( 59.38%) alltests-1800 16068.06 ( 0.00%) 25599.71 ( 59.32%) alltests-1900 16046.94 ( 0.00%) 25525.92 ( 59.07%) alltests-2000 16007.26 ( 0.00%) 25513.07 ( 59.38%) disk-100 7582.14 ( 0.00%) 7257.48 ( -4.28%) disk-200 6962.44 ( 0.00%) 7109.15 ( 2.11%) disk-300 6435.93 ( 0.00%) 6904.75 ( 7.28%) disk-400 6370.84 ( 0.00%) 6861.26 ( 7.70%) disk-500 6353.42 ( 0.00%) 6846.71 ( 7.76%) disk-600 6368.82 ( 0.00%) 6806.75 ( 6.88%) disk-700 6331.37 ( 0.00%) 6796.01 ( 7.34%) disk-800 6324.22 ( 0.00%) 6788.00 ( 7.33%) disk-900 6253.52 ( 0.00%) 6750.43 ( 7.95%) disk-1000 6242.53 ( 0.00%) 6855.11 ( 9.81%) disk-1100 6234.75 ( 0.00%) 6858.47 ( 10.00%) disk-1200 6312.76 ( 0.00%) 6845.13 ( 8.43%) disk-1300 6309.95 ( 0.00%) 6834.51 ( 8.31%) disk-1400 6171.76 ( 0.00%) 6787.09 ( 9.97%) disk-1500 6139.81 ( 0.00%) 6761.09 ( 10.12%) disk-1600 4807.12 ( 0.00%) 6725.33 ( 39.90%) disk-1700 4669.50 ( 0.00%) 5985.38 ( 28.18%) disk-1800 4663.51 ( 0.00%) 5972.99 ( 28.08%) disk-1900 4674.31 ( 0.00%) 5949.94 ( 27.29%) disk-2000 4668.36 ( 0.00%) 5834.93 ( 24.99%) In addition, a 67.5% increase in successfully migrated NUMA pages, thus improving node locality. The patch layout is simple but designed for bisection (in case reversion is needed if the changes break upstream) and easier review: o Patches 1-4 convert the i_mmap lock from mutex to rwsem. o Patches 5-10 share the lock in specific paths, each patch details the rationale behind why it should be safe. This patchset has been tested with: postgres 9.4 (with brand new hugetlb support), hugetlbfs test suite (all tests pass, in fact more tests pass with these changes than with an upstream kernel), ltp, aim7 benchmarks, memcached and iozone with the -B option for mmap'ing. *Untested* paths are nommu, memory-failure, uprobes and xip. Applies on top of Linus' latest (3.18-rc1+c3351dfabf5c). Thanks! Davidlohr Bueso (10): mm,fs: introduce helpers around the i_mmap_mutex mm: use new helper functions around the i_mmap_mutex mm: convert i_mmap_mutex to rwsem mm/rmap: share the i_mmap_rwsem uprobes: share the i_mmap_rwsem mm/xip: share the i_mmap_rwsem mm/memory-failure: share the i_mmap_rwsem mm/mremap: share the i_mmap_rwsem mm/nommu: share the i_mmap_rwsem mm/hugetlb: share the i_mmap_rwsem fs/hugetlbfs/inode.c | 14 +++++++------- fs/inode.c | 2 +- include/linux/fs.h | 23 ++++++++++++++++++++++- include/linux/mmu_notifier.h | 2 +- kernel/events/uprobes.c | 6 +++--- kernel/fork.c | 4 ++-- mm/filemap.c | 10 +++++----- mm/filemap_xip.c | 23 +++++++++-------------- mm/fremap.c | 4 ++-- mm/hugetlb.c | 22 +++++++++++----------- mm/memory-failure.c | 4 ++-- mm/memory.c | 8 ++++---- mm/mmap.c | 22 +++++++++++----------- mm/mremap.c | 6 +++--- mm/nommu.c | 17 ++++++++--------- mm/rmap.c | 12 ++++++------ 16 files changed, 97 insertions(+), 82 deletions(-) -- 1.8.4.5 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. 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