Date:	Mon, 13 Apr 2015 10:02:02 +0300
From:	Leon Romanovsky <leon@...n.nu>
To:	Wang YanQing <udknight@...il.com>, axboe@...nel.dk,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Linux-MM <linux-mm@...ck.org>
Subject: Re: [PATCH RESEND] block:bounce: fix call inc_|dec_zone_page_state on
 different pages confuse value of NR_BOUNCE

On Sat, Mar 7, 2015 at 2:18 AM, Wang YanQing <udknight@...il.com> wrote:
>
> Commit d2c5e30c9a1420902262aa923794d2ae4e0bc391
> ("[PATCH] zoned vm counters: conversion of nr_bounce to per zone counter")
> convert statistic of nr_bounce to per zone and one global value in vm_stat,
> but it call call inc_|dec_zone_page_state on different pages, then different
Minor typo "call call" => "call"

> zones, and cause we get confusion value of NR_BOUNCE.
I suggest to rephrase the "and cause we get confusion value" to be
"and cause us to get unexpected value".

>
> Below is the result on my machine:
> Mar  2 09:26:08 udknight kernel: [144766.778265] Mem-Info:
> Mar  2 09:26:08 udknight kernel: [144766.778266] DMA per-cpu:
> Mar  2 09:26:08 udknight kernel: [144766.778268] CPU    0: hi:    0, btch:   1 usd:   0
> Mar  2 09:26:08 udknight kernel: [144766.778269] CPU    1: hi:    0, btch:   1 usd:   0
> Mar  2 09:26:08 udknight kernel: [144766.778270] Normal per-cpu:
> Mar  2 09:26:08 udknight kernel: [144766.778271] CPU    0: hi:  186, btch:  31 usd:   0
> Mar  2 09:26:08 udknight kernel: [144766.778273] CPU    1: hi:  186, btch:  31 usd:   0
> Mar  2 09:26:08 udknight kernel: [144766.778274] HighMem per-cpu:
> Mar  2 09:26:08 udknight kernel: [144766.778275] CPU    0: hi:  186, btch:  31 usd:   0
> Mar  2 09:26:08 udknight kernel: [144766.778276] CPU    1: hi:  186, btch:  31 usd:   0
> Mar  2 09:26:08 udknight kernel: [144766.778279] active_anon:46926 inactive_anon:287406 isolated_anon:0
> Mar  2 09:26:08 udknight kernel: [144766.778279]  active_file:105085 inactive_file:139432 isolated_file:0
> Mar  2 09:26:08 udknight kernel: [144766.778279]  unevictable:653 dirty:0 writeback:0 unstable:0
> Mar  2 09:26:08 udknight kernel: [144766.778279]  free:178957 slab_reclaimable:6419 slab_unreclaimable:9966
> Mar  2 09:26:08 udknight kernel: [144766.778279]  mapped:4426 shmem:305277 pagetables:784 bounce:0
> Mar  2 09:26:08 udknight kernel: [144766.778279]  free_cma:0
> Mar  2 09:26:08 udknight kernel: [144766.778286] DMA free:3324kB min:68kB low:84kB high:100kB active_anon:0kB inactive_anon:0kB active_file:0kB inactive_file:0kB unevictable:0kB isolated(anon):0kB isolated(file):0kB present:15976kB managed:15900kB mlocked:0kB dirty:0kB writeback:0kB mapped:0kB shmem:0kB slab_reclaimable:0kB slab_unreclaimable:0kB kernel_stack:0kB pagetables:0kB unstable:0kB bounce:0kB free_cma:0kB writeback_tmp:0kB pages_scanned:0 all_unreclaimable? yes
> Mar  2 09:26:08 udknight kernel: [144766.778287] lowmem_reserve[]: 0 822 3754 3754
> Mar  2 09:26:08 udknight kernel: [144766.778293] Normal free:26828kB min:3632kB low:4540kB high:5448kB active_anon:4872kB inactive_anon:68kB active_file:1796kB inactive_file:1796kB unevictable:0kB isolated(anon):0kB isolated(file):0kB present:892920kB managed:842560kB mlocked:0kB dirty:0kB writeback:0kB mapped:0kB shmem:4144kB slab_reclaimable:25676kB slab_unreclaimable:39864kB kernel_stack:1944kB pagetables:3136kB unstable:0kB bounce:0kB free_cma:0kB writeback_tmp:0kB pages_scanned:2412612 all_unreclaimable? yes
> Mar  2 09:26:08 udknight kernel: [144766.778294] lowmem_reserve[]: 0 0 23451 23451
> Mar  2 09:26:08 udknight kernel: [144766.778299] HighMem free:685676kB min:512kB low:3748kB high:6984kB active_anon:182832kB inactive_anon:1149556kB active_file:418544kB inactive_file:555932kB unevictable:2612kB isolated(anon):0kB isolated(file):0kB present:3001732kB managed:3001732kB mlocked:0kB dirty:0kB writeback:0kB mapped:17704kB shmem:1216964kB slab_reclaimable:0kB slab_unreclaimable:0kB kernel_stack:0kB pagetables:0kB unstable:0kB bounce:75771152kB free_cma:0kB writeback_tmp:0kB pages_scanned:0 all_unreclaimable? no
> Mar  2 09:26:08 udknight kernel: [144766.778300] lowmem_reserve[]: 0 0 0 0
>
> You can see bounce:75771152kB for HighMem, but bounce:0 for lowmem and global.
>
> This patch fix it.
>
> Signed-off-by: Wang YanQing <udknight@...il.com>
> ---
>  I find previous email can't be "git am" properly,
>  so resend it.
>
>  Thanks.
>
>  block/bounce.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/block/bounce.c b/block/bounce.c
> index ab21ba2..ed9dd80 100644
> --- a/block/bounce.c
> +++ b/block/bounce.c
> @@ -221,8 +221,8 @@ bounce:
>                 if (page_to_pfn(page) <= queue_bounce_pfn(q) && !force)
>                         continue;
>
> -               inc_zone_page_state(to->bv_page, NR_BOUNCE);
>                 to->bv_page = mempool_alloc(pool, q->bounce_gfp);
> +               inc_zone_page_state(to->bv_page, NR_BOUNCE);
>
>                 if (rw == WRITE) {
>                         char *vto, *vfrom;
> --
> 2.2.2.dirty
>
> --
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-- 
Leon Romanovsky | Independent Linux Consultant
        www.leon.nu | leon@...n.nu
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