linux-kernel - Re: [PATCH] mm: do not sleep in balance

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Message-ID: <CAJd=RBCQN1GxOUCwGPXL27d_q8hv50uHK5LhDnsv7mdv_2Usaw@mail.gmail.com>
Date:	Fri, 21 Dec 2012 19:51:31 +0800
From:	Hillf Danton <dhillf@...il.com>
To:	Zlatko Calusic <zlatko.calusic@...on.hr>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Mel Gorman <mgorman@...e.de>, Hugh Dickins <hughd@...gle.com>,
	linux-mm <linux-mm@...ck.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] mm: do not sleep in balance_pgdat if there's no i/o congestion

On Thu, Dec 20, 2012 at 7:25 AM, Zlatko Calusic <zlatko.calusic@...on.hr> wrote:
>  static unsigned long balance_pgdat(pg_data_t *pgdat, int order,
>                                                         int *classzone_idx)
>  {
> -       int all_zones_ok;
> +       struct zone *unbalanced_zone;

nit: less hunks if not erase that mark

Hillf
>         unsigned long balanced;
>         int i;
>         int end_zone = 0;       /* Inclusive.  0 = ZONE_DMA */
> @@ -2580,7 +2580,7 @@ loop_again:
>                 unsigned long lru_pages = 0;
>                 int has_under_min_watermark_zone = 0;
>
> -               all_zones_ok = 1;
> +               unbalanced_zone = NULL;
>                 balanced = 0;
>
>                 /*
> @@ -2719,7 +2719,7 @@ loop_again:
>                         }
>
>                         if (!zone_balanced(zone, testorder, 0, end_zone)) {
> -                               all_zones_ok = 0;
> +                               unbalanced_zone = zone;
>                                 /*
>                                  * We are still under min water mark.  This
>                                  * means that we have a GFP_ATOMIC allocation
> @@ -2752,7 +2752,7 @@ loop_again:
>                                 pfmemalloc_watermark_ok(pgdat))
>                         wake_up(&pgdat->pfmemalloc_wait);
>
> -               if (all_zones_ok || (order && pgdat_balanced(pgdat, balanced, *classzone_idx)))
> +               if (!unbalanced_zone || (order && pgdat_balanced(pgdat, balanced, *classzone_idx)))
>                         break;          /* kswapd: all done */
>                 /*
>                  * OK, kswapd is getting into trouble.  Take a nap, then take
> @@ -2762,7 +2762,7 @@ loop_again:
>                         if (has_under_min_watermark_zone)
>                                 count_vm_event(KSWAPD_SKIP_CONGESTION_WAIT);
>                         else
> -                               congestion_wait(BLK_RW_ASYNC, HZ/10);
> +                               wait_iff_congested(unbalanced_zone, BLK_RW_ASYNC, HZ/10);
>                 }
>
>                 /*
> @@ -2781,7 +2781,7 @@ out:
>          * high-order: Balanced zones must make up at least 25% of the node
>          *             for the node to be balanced
>          */
> -       if (!(all_zones_ok || (order && pgdat_balanced(pgdat, balanced, *classzone_idx)))) {
> +       if (unbalanced_zone && (!order || !pgdat_balanced(pgdat, balanced, *classzone_idx))) {
>                 cond_resched();
>
>                 try_to_freeze();
> -- 1.7.10.4
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