On 12/04/2012 05:11 PM, Johannes Weiner wrote:
> On Tue, Dec 04, 2012 at 10:15:09AM +0100, Jiri Slaby wrote:
>> It does not apply to -next :/. Should I try anything else?
>
> The COMPACTION_BUILD changed to IS_ENABLED(CONFIG_COMPACTION), below
> is a -next patch. I hope you don't run into other problems that come
> out of -next craziness, because Linus is kinda waiting for this to be
> resolved to release 3.8. If you've always tested against -next so far
> and it worked otherwise, don't change the environment now, please. If
> you just started, it would make more sense to test based on 3.7-rc8.
>
> Thanks!
>
> ---
> From: Johannes Weiner <hannes@xxxxxxxxxxx>
> Subject: [patch] mm: vmscan: do not keep kswapd looping forever due
> to individual uncompactable zones
>
> When a zone meets its high watermark and is compactable in case of
> higher order allocations, it contributes to the percentage of the
> node's memory that is considered balanced.
>
> This requirement, that a node be only partially balanced, came about
> when kswapd was desparately trying to balance tiny zones when all
> bigger zones in the node had plenty of free memory. Arguably, the
> same should apply to compaction: if a significant part of the node is
> balanced enough to run compaction, do not get hung up on that tiny
> zone that might never get in shape.
>
> When the compaction logic in kswapd is reached, we know that at least
> 25% of the node's memory is balanced properly for compaction (see
> zone_balanced and pgdat_balanced). Remove the individual zone checks
> that restart the kswapd cycle.
>
> Otherwise, we may observe more endless looping in kswapd where the
> compaction code loops back to reclaim because of a single zone and
> reclaim does nothing because the node is considered balanced overall.
>
> Reported-by: Thorsten Leemhuis <fedora@xxxxxxxxxxxxx>
> Signed-off-by: Johannes Weiner <hannes@xxxxxxxxxxx>
Looks like it's gone with this patch now. Hopefully the send button
won't trigger the issue the same as the last time :).
> ---
> mm/vmscan.c | 16 ----------------
> 1 file changed, 16 deletions(-)
>
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index 3b0aef4..486100f 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -2806,22 +2806,6 @@ static unsigned long balance_pgdat(pg_data_t *pgdat, int order,
> if (!populated_zone(zone))
> continue;
>
> - if (zone->all_unreclaimable &&
> - sc.priority != DEF_PRIORITY)
> - continue;
> -
> - /* Would compaction fail due to lack of free memory? */
> - if (IS_ENABLED(CONFIG_COMPACTION) &&
> - compaction_suitable(zone, order) == COMPACT_SKIPPED)
> - goto loop_again;
> -
> - /* Confirm the zone is balanced for order-0 */
> - if (!zone_watermark_ok(zone, 0,
> - high_wmark_pages(zone), 0, 0)) {
> - order = sc.order = 0;
> - goto loop_again;
> - }
> -
> /* Check if the memory needs to be defragmented. */
> if (zone_watermark_ok(zone, order,
> low_wmark_pages(zone), *classzone_idx, 0))
>
--
js
suse labs
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