On Tue, Aug 31, 2010 at 10:18 AM, KOSAKI Motohiro
<kosaki.motohiro@xxxxxxxxxxxxxx> wrote:
>> Hi, KOSAKI.
>>
>> On Tue, Aug 31, 2010 at 9:56 AM, KOSAKI Motohiro
>> <kosaki.motohiro@xxxxxxxxxxxxxx> wrote:
>> >> diff --git a/mm/vmscan.c b/mm/vmscan.c
>> >> index 1b145e6..0b8a3ce 100644
>> >> --- a/mm/vmscan.c
>> >> +++ b/mm/vmscan.c
>> >> @@ -1747,7 +1747,7 @@ static void shrink_zone(int priority, struct zone *zone,
>> >> * Even if we did not try to evict anon pages at all, we want to
>> >> * rebalance the anon lru active/inactive ratio.
>> >> */
>> >> - if (inactive_anon_is_low(zone, sc) && nr_swap_pages > 0)
>> >> + if (nr_swap_pges > 0 && inactive_anon_is_low(zone, sc))
>> >
>> > Sorry, I don't find any difference. What is your intention?
>> >
>>
>> My intention is that smart gcc can compile out inactive_anon_is_low
>> call in case of non swap configurable system.
>
> Do you really check it on your gcc? nr_swap_pages is not file scope variable, it's
> global variable. afaik, current gcc's link time optimization is not so cool.
#else /* CONFIG_SWAP */
#define nr_swap_pages 0L
#define total_swap_pages 0L
#define total_swapcache_pages 0UL
>
> Do you have a disassemble list?
>
environment for test :
gcc : arm-none-linux-gnueabi-gcc (Sourcery G++ Lite 2009q3-67) 4.4.1
kernel : 2.6.28(for test, I used my working kernel version with my patch)
assembled function is shrink_zone.
(Please understand web gmail's contents mangling. Google guys! Please
repair for like me who can't use SMTP in company. :( )
1. swap configurable version
1cd0: e51b303c ldr r3, [fp, #-60] ; 0x3c
1cd4: e3530000 cmp r3, #0
1cd8: 1affffd1 bne 1c24 <shrink_zone+0x23c>
1cdc: e5879004 str r9, [r7, #4]
1ce0: e1a00008 mov r0, r8
1ce4: e1a01007 mov r1, r7
1ce8: e1a04008 mov r4, r8
1cec: ebfff8eb bl a0 <inactive_anon_is_low> <==
1cf0: e1a05007 mov r5, r7
1cf4: e3500000 cmp r0, #0
1cf8: 0a000006 beq 1d18 <shrink_zone+0x330>
1cfc: e1a01008 mov r1, r8
1d00: e1a03006 mov r3, r6
1d04: e3a00020 mov r0, #32
1d08: e1a02007 mov r2, r7
1d0c: e3a0c000 mov ip, #0
1d10: e58dc000 str ip, [sp]
1d14: ebfffa98 bl 77c <shrink_active_list>
1d18: e5950008 ldr r0, [r5, #8]
1d1c: ebfffffe bl 0 <throttle_vm_writeout>
1d20: e24bd028 sub sp, fp, #40 ; 0x28
2. non swap configurable version
1994: e3530000 cmp r3, #0
1998: 0a000003 beq 19ac <shrink_zone+0x170>
199c: e598300c ldr r3, [r8, #12]
19a0: e593300c ldr r3, [r3, #12]
19a4: e3130701 tst r3, #262144 ; 0x40000
19a8: 0a000008 beq 19d0 <shrink_zone+0x194>
19ac: e51b3044 ldr r3, [fp, #-68] ; 0x44
19b0: e3530000 cmp r3, #0
19b4: 1affffd7 bne 1918 <shrink_zone+0xdc>
19b8: e51b3038 ldr r3, [fp, #-56] ; 0x38
19bc: e3530000 cmp r3, #0
19c0: 1affffd4 bne 1918 <shrink_zone+0xdc>
19c4: e51b303c ldr r3, [fp, #-60] ; 0x3c
19c8: e3530000 cmp r3, #0
19cc: 1affffd1 bne 1918 <shrink_zone+0xdc>
19d0: e586a004 str sl, [r6, #4]
19d4: e1a04006 mov r4, r6
19d8: e5960008 ldr r0, [r6, #8]
19dc: ebfffffe bl 0 <throttle_vm_writeout>
19e0: e24bd028 sub sp, fp, #40 ; 0x28
--
Kind regards,
Minchan Kim
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