Messages in this thread | | | Date | Sat, 10 Mar 2012 10:55:44 +0400 | From | Konstantin Khlebnikov <> | Subject | Re: [PATCH 3/7 v2] mm: rework __isolate_lru_page() file/anon filter |
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Hugh Dickins wrote: > On Fri, 9 Mar 2012, Konstantin Khlebnikov wrote: >> Hugh Dickins wrote: >>> >>> I like very much the look of what he's come up with, but I'm still >>> puzzling over why it barely makes any improvement to __isolate_lru_page(): >>> seems significantly inferior (in code size terms) to his original (which >>> I imagine Glauber's compromise would be equivalent to). >>> >>> At some point I ought to give up on niggling about this, >>> but I haven't quite got there yet. >> >> (with if()) >> $ ./scripts/bloat-o-meter built-in.o built-in.o-v1 >> add/remove: 0/0 grow/shrink: 2/1 up/down: 32/-20 (12) >> function old new delta >> static.shrink_active_list 837 853 +16 >> shrink_inactive_list 1259 1275 +16 >> static.isolate_lru_pages 1055 1035 -20 >> >> (with switch()) >> $ ./scripts/bloat-o-meter built-in.o built-in.o-v2 >> add/remove: 0/0 grow/shrink: 4/2 up/down: 111/-23 (88) >> function old new delta >> __isolate_lru_page 301 377 +76 >> static.shrink_active_list 837 853 +16 >> shrink_inactive_list 1259 1275 +16 >> page_evictable 170 173 +3 >> __remove_mapping 322 319 -3 >> static.isolate_lru_pages 1055 1035 -20 >> >> (without __always_inline on page_lru()) >> $ ./scripts/bloat-o-meter built-in.o built-in.o-v5-noinline >> add/remove: 0/0 grow/shrink: 5/2 up/down: 93/-23 (70) >> function old new delta >> __isolate_lru_page 301 333 +32 >> isolate_lru_page 359 385 +26 >> static.shrink_active_list 837 853 +16 >> putback_inactive_pages 635 651 +16 >> page_evictable 170 173 +3 >> __remove_mapping 322 319 -3 >> static.isolate_lru_pages 1055 1035 -20 >> >> $ ./scripts/bloat-o-meter built-in.o built-in.o-v5 >> add/remove: 0/0 grow/shrink: 3/4 up/down: 35/-67 (-32) >> function old new delta >> static.shrink_active_list 837 853 +16 >> __isolate_lru_page 301 317 +16 >> page_evictable 170 173 +3 >> __remove_mapping 322 319 -3 >> mem_cgroup_lru_del 73 65 -8 >> static.isolate_lru_pages 1055 1035 -20 >> __mem_cgroup_commit_charge 676 640 -36 >> >> Actually __isolate_lru_page() even little bit bigger > > I was coming to realize that it must be your page_lru()ing: > although it's dressed up in one line, there's several branches there.
Yes, but I think we can optimize page_lru(): we can prepare ready-to-use page lru index in lower bits of page->flags, if we swap page flags and split LRU_UNEVICTABLE into FILE/ANON parts.
> > I think you'll find you have a clear winner at last, if you just pass > lru on down as third arg to __isolate_lru_page(), where file used to > be passed, instead of re-evaluating it inside. > > shrink callers already have the lru, and compaction works it out > immediately afterwards.
No, for non-lumpy isolation we don't need this check at all, because all pages already picked from right lru list.
I'll send separate patch for this (on top v5 patchset), after meditation =)
> > Though we do need to be careful: the lumpy case would then have to > pass page_lru(cursor_page). Oh, actually no (though it would deserve > a comment): since the lumpy case selects LRU_ALL_EVICTABLE, it's > irrelevant what it passes for lru, so might as well stick with > the one passed down. Though you may decide I'm being too tricky > there, and prefer to calculate page_lru(cursor_page) anyway, it > not being the hottest path. > > Whether you'd still want page_lru(page) __always_inline, I don't know. > > Hugh
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