Messages in this thread | | | From | KOSAKI Motohiro <> | Subject | Re: [PATCH 2/3] vmscan: make mapped executable pages the first class citizen | Date | Tue, 19 May 2009 13:41:38 +0900 (JST) |
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Hi
Thanks for great works.
> SUMMARY > ======= > The patch decreases the number of major faults from 50 to 3 during 10% cache hot reads. > > > SCENARIO > ======== > The test scenario is to do 100000 pread(size=110 pages, offset=(i*100) pages), > where 10% of the pages will be activated: > > for i in `seq 0 100 10000000`; do echo $i 110; done > pattern-hot-10 > iotrace.rb --load pattern-hot-10 --play /b/sparse
Which can I download iotrace.rb?
> and monitor /proc/vmstat during the time. The test box has 2G memory. > > > ANALYZES > ======== > > I carried out two runs on fresh booted console mode 2.6.29 with the VM_EXEC > patch, and fetched the vmstat numbers on > > (1) begin: shortly after the big read IO starts; > (2) end: just before the big read IO stops; > (3) restore: the big read IO stops and the zsh working set restored > > nr_mapped nr_active_file nr_inactive_file pgmajfault pgdeactivate pgfree > begin: 2481 2237 8694 630 0 574299 > end: 275 231976 233914 633 776271 20933042 > restore: 370 232154 234524 691 777183 20958453 > > begin: 2434 2237 8493 629 0 574195 > end: 284 231970 233536 632 771918 20896129 > restore: 399 232218 234789 690 774526 20957909 > > and another run on 2.6.30-rc4-mm with the VM_EXEC logic disabled:
I don't think it is proper comparision. you need either following comparision. otherwise we insert many guess into the analysis.
- 2.6.29 with and without VM_EXEC patch - 2.6.30-rc4-mm with and without VM_EXEC patch
> > begin: 2479 2344 9659 210 0 579643 > end: 284 232010 234142 260 772776 20917184 > restore: 379 232159 234371 301 774888 20967849 > > The numbers show that > > - The startup pgmajfault of 2.6.30-rc4-mm is merely 1/3 that of 2.6.29. > I'd attribute that improvement to the mmap readahead improvements :-) > > - The pgmajfault increment during the file copy is 633-630=3 vs 260-210=50. > That's a huge improvement - which means with the VM_EXEC protection logic, > active mmap pages is pretty safe even under partially cache hot streaming IO. > > - when active:inactive file lru size reaches 1:1, their scan rates is 1:20.8 > under 10% cache hot IO. (computed with formula Dpgdeactivate:Dpgfree) > That roughly means the active mmap pages get 20.8 more chances to get > re-referenced to stay in memory. > > - The absolute nr_mapped drops considerably to 1/9 during the big IO, and the > dropped pages are mostly inactive ones. The patch has almost no impact in > this aspect, that means it won't unnecessarily increase memory pressure. > (In contrast, your 20% mmap protection ratio will keep them all, and > therefore eliminate the extra 41 major faults to restore working set > of zsh etc.)
I'm surprised this. Why your patch don't protect mapped page from streaming io?
I strongly hope reproduce myself, please teach me reproduce way.
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