linux-kernel - Re: [PATCH 3/7 v2] mm: rework __isolate_lru

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Date:	Fri, 09 Mar 2012 11:16:12 +0400
From:	Konstantin Khlebnikov <khlebnikov@...nvz.org>
To:	Hugh Dickins <hughd@...gle.com>
CC:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Johannes Weiner <jweiner@...hat.com>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 3/7 v2] mm: rework __isolate_lru_page() file/anon filter

Hugh Dickins wrote:
> On Thu, 8 Mar 2012, KAMEZAWA Hiroyuki wrote:
>> On Tue, 6 Mar 2012 19:22:21 -0800 (PST)
>> Hugh Dickins<hughd@...gle.com>  wrote:
>>>
>>> What does the compiler say (4.5.1 here, OPTIMIZE_FOR_SIZE off)?
>>>     text	   data	    bss	    dec	    hex	filename
>>>    17723	    113	     17	  17853	   45bd	vmscan.o.0
>>>    17671	    113	     17	  17801	   4589	vmscan.o.1
>>>    17803	    113	     17	  17933	   460d	vmscan.o.2
>>>
>>> That suggests that your v2 is the worst and your v1 the best.
>>> Kame, can I persuade you to let the compiler decide on this?
>>>
>>
>> Hmm. How about Costa' proposal ? as
>>
>> int tmp_var = PageActive(page) ? ISOLATE_ACTIVE : ISOLATE_INACTIVE
>> if (!(mode&  tmp_var))
>>      ret;
>
> Yes, that would have been a good compromise (given a better name
> than "tmp_var"!), I didn't realize that one was acceptable to you.
>
> But I see that Konstantin has been inspired by our disagreement to a
> more creative solution.
>
> 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

>
> Hugh

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