Messages in this thread | | | Date | Wed, 8 Apr 2009 13:02:23 -0700 | Subject | [PATCH][0/2]page_fault retry with NOPAGE_RETRY | From | Ying Han <> |
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changelog[v3]: - applied fixes and cleanups from Wu Fengguang. filemap VM_FAULT_RETRY fixes [PATCH 01/14] mm: fix find_lock_page_retry() return value parsing [PATCH 02/14] mm: fix major/minor fault accounting on retried fault [PATCH 04/14] mm: reduce duplicate page fault code [PATCH 05/14] readahead: account mmap_miss for VM_FAULT_RETRY
- split the patch into two parts. first part includes FAULT_FLAG_RETRY support with no current user change. second part includes individual per-architecture cleanups that enable FAULT_FLAG_RETRY. currently there are mainly two users for handle_mm_fault, we enable FAULT_FLAG_RETRY for actual fault handler and leave get_user_pages unchanged.
Benchmarks: posted on [V1]: case 1. one application has a high count of threads each faulting in different pages of a hugefile. Benchmark indicate that this double data structure walking in case of major fault results in << 1% performance hit.
case 2. add another thread in the above application which in a tight loop of mmap()/munmap(). Here we measure loop count in the new thread while other threads doing the same amount of work as case one. we got << 3% performance hit on the Complete Time(benchmark value for case one) and 10% performance improvement on the mmap()/munmap() counter.
This patch helps a lot in cases we have writer which is waitting behind all readers, so it could execute much faster.
some new test results from Wufengguang: Just tested the sparse-random-read-on-sparse-file case, and found the performance impact to be 0.4% (8.706s vs 8.744s). Kind of acceptable.
without FAULT_FLAG_RETRY: iotrace.rb --load stride-100 --mplay /mnt/btrfs-ram/sparse 3.28s user 5.39s system 99% cpu 8.692 total iotrace.rb --load stride-100 --mplay /mnt/btrfs-ram/sparse 3.17s user 5.54s system 99% cpu 8.742 total iotrace.rb --load stride-100 --mplay /mnt/btrfs-ram/sparse 3.18s user 5.48s system 99% cpu 8.684 total
FAULT_FLAG_RETRY: iotrace.rb --load stride-100 --mplay /mnt/btrfs-ram/sparse 3.18s user 5.63s system 99% cpu 8.825 total iotrace.rb --load stride-100 --mplay /mnt/btrfs-ram/sparse 3.22s user 5.47s system 99% cpu 8.718 total iotrace.rb --load stride-100 --mplay /mnt/btrfs-ram/sparse 3.13s user 5.55s system 99% cpu 8.690 total
In the above faked workload, the mmap read page offsets are loaded from stride-100 and performed on /mnt/btrfs-ram/sparse, which are created by:
seq 0 100 1000000 > stride-100 dd if=/dev/zero of=/mnt/btrfs-ram/sparse bs=1M count=1 seek=1024000
Signed-off-by: Ying Han <yinghan@google.com> Mike Waychison <mikew@google.com>
arch/x86/mm/fault.c | 20 ++++++++++++++ include/linux/fs.h | 2 +- include/linux/mm.h | 2 + mm/filemap.c | 72 ++++++++++++++++++++++++++++++++++++++++++++++++-- mm/memory.c | 33 +++++++++++++++++------ 5 files changed, 116 insertions(+), 13 deletions(-)
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