From: Mel Gorman <mgorman@techsingularity.net>
To: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Vlastimil Babka <vbabka@suse.cz>, linux-mm <linux-mm@kvack.org>
Subject: Re: [PATCH v2] mm/page_alloc: don't wake kswapd from rmqueue() unless __GFP_KSWAPD_RECLAIM is specified
Date: Mon, 15 May 2023 08:38:40 +0100 [thread overview]
Message-ID: <20230515073840.6yos3cisg2rlyw6i@techsingularity.net> (raw)
In-Reply-To: <c3c3dacf-dd3b-77c9-f96a-d0982b4b2a4f@I-love.SAKURA.ne.jp>
On Sun, May 14, 2023 at 09:28:56AM +0900, Tetsuo Handa wrote:
> Commit 73444bc4d8f9 ("mm, page_alloc: do not wake kswapd with zone lock
> held") moved wakeup_kswapd() from steal_suitable_fallback() to rmqueue()
> using ZONE_BOOSTED_WATERMARK flag.
>
> Only allocation contexts that include ALLOC_KSWAPD (which corresponds to
> __GFP_KSWAPD_RECLAIM) should wake kswapd, for callers are supposed to
> remove __GFP_KSWAPD_RECLAIM if trying to hold pgdat->kswapd_wait has a
> risk of deadlock.
kswapd_wait is a waitqueue so what is being held? It's safe for kswapd
to try wake itself as the waitqueue will be active when wakeup_kswapd()
is called so no wakeup occurs. If there is a deadlock, it needs a better
explanation. I believe I already stated why this patch is fixing a bug
but it wasn't deadlock related.
--
Mel Gorman
SUSE Labs
next prev parent reply other threads:[~2023-05-15 7:38 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-05-11 13:47 [PATCH] mm/page_alloc: don't wake up kswapd from rmqueue() unless __GFP_KSWAPD_RECLAIM is specified Tetsuo Handa
2023-05-12 3:45 ` Andrew Morton
2023-05-13 9:38 ` Tetsuo Handa
2023-05-13 10:23 ` Mel Gorman
2023-05-14 0:28 ` [PATCH v2] mm/page_alloc: don't wake " Tetsuo Handa
2023-05-15 6:03 ` Huang, Ying
2023-05-15 6:35 ` Huang, Ying
2023-05-15 7:38 ` Mel Gorman [this message]
2023-05-15 10:17 ` Tetsuo Handa
2023-05-16 1:44 ` Huang, Ying
2023-05-22 13:57 ` Tetsuo Handa
2023-05-22 14:58 ` Mel Gorman
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