Messages in this thread |  | | | Date | Sat, 06 Dec 2008 11:55:40 +0200 | | From | Török Edwin <> | | Subject | Re: [RFC v2][PATCH]page_fault retry with NOPAGE_RETRY |
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On 2008-12-06 11:52, Török Edwin wrote: > On 2008-12-05 21:40, Ying Han wrote: > >> changelog[v2]: >> - reduce the runtime overhead by extending the 'write' flag of >> handle_mm_fault() to indicate the retry hint. >> - add another two branches in filemap_fault with retry logic. >> - replace find_lock_page with find_lock_page_retry to make the code >> cleaner. >> >> todo: >> - there is potential a starvation hole with the retry. By the time the >> retry returns, the pages might be released. we can make change by holding >> page reference as well as remembering what the page "was"(in case the >> file was truncated). any suggestion here are welcomed. >> >> I also made patches for all other arch. I am posting x86_64 here first and >> i will post others by the time everyone feels comfortable of this patch. >> >> Edwin, please test this patch with your testcase and check if you get any >> performance improvement of mmap over read. I added another two more places >> in filemap_fault with retry logic which you might hit in your privous >> experiment. >> >> > > I get much better results with this patch than with v1, thanks! > > mmap now scales almost as well as read does (there is a small ~5% > overhead), which is a significant improvement over not scaling at all! > > Here are the results when running my testcase: > > Number of threads ->, 1,,, 2,,, 4,,, 8,,, 16 > Kernel version, read, mmap, mixed, read, mmap, mixed, read, mmap, mixed, > read, mmap, mixed, read, mmap, mixed > 2.6.28-rc7-tip, 27.55, 26.18, 27.06, 16.18, 16.97, 16.10, 11.06, 11.64, > 11.41, 9.38, 9.97, 9.31, 9.37, 9.82, 9.3 > > > Here are the /proc/lock_stat output when running my testcase, contention > is lower (34911+10462 vs 58590+7231), and waittime-total is better > (57 601 464 vs 234 170 024) > > lock_stat version 0.3 > ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- > class name con-bounces contentions > waittime-min waittime-max waittime-total acq-bounces > acquisitions holdtime-min holdtime-max holdtime-total > ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- > &mm->mmap_sem-W: 5843 > 10462 2.89 138824.72 14217159.52 > 18965 84205 1.81 5031.07 725293.65 > &mm->mmap_sem-R: 20208 > 34911 4.87 136797.26 57601464.49 55797 > 1110394 1.89 164918.52 30551371.71 > --------------- > &mm->mmap_sem 5341 > [<ffffffff802bf9d7>] sys_munmap+0x47/0x80 > &mm->mmap_sem 28579 > [<ffffffff805d1c62>] do_page_fault+0x172/0xab0 > &mm->mmap_sem 5030 > [<ffffffff80211161>] sys_mmap+0xf1/0x140 > &mm->mmap_sem 6331 > [<ffffffff802a675e>] find_lock_page_retry+0xde/0xf0 > --------------- > &mm->mmap_sem 13558 > [<ffffffff802a675e>] find_lock_page_retry+0xde/0xf0 > &mm->mmap_sem 4694 > [<ffffffff802bf9d7>] sys_munmap+0x47/0x80 > &mm->mmap_sem 3681 > [<ffffffff80211161>] sys_mmap+0xf1/0x140 > &mm->mmap_sem 23374 > [<ffffffff805d1c62>] do_page_fault+0x172/0xab0 > > > On clamd: > > Here holdtime-total is better (1 493 154 + 2 395 987 vs 2 087 538 + 2 > 514 673), and number of contentions on read > (458 052 vs 5851
typo, should have been: 458 052 vs 585 119
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