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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