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From: Jiri Slaby <jirislaby@kernel.org>
To: Andrew Morton <akpm@linux-foundation.org>,
	mm-commits@vger.kernel.org, zhouchuyi@bytedance.com,
	stable@vger.kernel.org, regressions@leemhuis.info,
	pbonzini@redhat.com, mlevitsk@redhat.com, mhocko@kernel.org,
	mgorman@techsingularity.net, vbabka@suse.cz
Subject: Re: + revert-mm-compaction-fix-set-skip-in-fast_find_migrateblock.patch added to mm-hotfixes-unstable branch
Date: Mon, 16 Jan 2023 06:46:32 +0100	[thread overview]
Message-ID: <e518370c-2926-e8ec-d25c-93b2b2304602@kernel.org> (raw)
In-Reply-To: <20230114041117.B372AC43392@smtp.kernel.org>

On 14. 01. 23, 5:11, Andrew Morton wrote:
> The patch titled
>       Subject: Revert "mm/compaction: fix set skip in fast_find_migrateblock"
> has been added to the -mm mm-hotfixes-unstable branch.  Its filename is
>       revert-mm-compaction-fix-set-skip-in-fast_find_migrateblock.patch
> 
> This patch will shortly appear at
>       https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/revert-mm-compaction-fix-set-skip-in-fast_find_migrateblock.patch
> 
> This patch will later appear in the mm-hotfixes-unstable branch at
>      git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
> 
> Before you just go and hit "reply", please:
>     a) Consider who else should be cc'ed
>     b) Prefer to cc a suitable mailing list as well
>     c) Ideally: find the original patch on the mailing list and do a
>        reply-to-all to that, adding suitable additional cc's
> 
> *** Remember to use Documentation/process/submit-checklist.rst when testing your code ***
> 
> The -mm tree is included into linux-next via the mm-everything
> branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
> and is updated there every 2-3 working days
> 
> ------------------------------------------------------
> From: Vlastimil Babka <vbabka@suse.cz>
> Subject: Revert "mm/compaction: fix set skip in fast_find_migrateblock"
> Date: Fri, 13 Jan 2023 18:33:45 +0100
> 
> This reverts commit 7efc3b7261030da79001c00d92bc3392fd6c664c.
> 
> We have got openSUSE reports (Link 1) for 6.1 kernel with khugepaged
> stalling CPU for long periods of time.  Investigation of tracepoint data
> shows that compaction is stuck in repeating fast_find_migrateblock() based
> migrate page isolation, and then fails to migrate all isolated pages.
> Commit 7efc3b726103 ("mm/compaction: fix set skip in
> fast_find_migrateblock") was suspected as it was merged in 6.1 and in
> theory can indeed remove a termination condition for
> fast_find_migrateblock() under certain conditions, as it removes a place
> that always marks a scanned pageblock from being re-scanned.  There are
> other such places, but those can be skipped under certain conditions,
> which seems to match the tracepoint data.
> 
> Testing of revert also appears to have resolved the issue, thus revert the
> commit until a more robust solution for the original problem is developed.




> It's also likely this will fix qemu stalls with 6.1 kernel reported in
> Link 2, but that is not yet confirmed.

Preliminary tests suggest this is also fixed:
Tested-by: Jiri Slaby <jirislaby@kernel.org>

> Link: https://bugzilla.suse.com/show_bug.cgi?id=1206848
> Link: https://lore.kernel.org/kvm/b8017e09-f336-3035-8344-c549086c2340@kernel.org/
> Link: https://lkml.kernel.org/r/20230113173345.9692-1-vbabka@suse.cz
> Fixes: 7efc3b726103 ("mm/compaction: fix set skip in fast_find_migrateblock")
> Cc: Chuyi Zhou <zhouchuyi@bytedance.com>
> Cc: Jiri Slaby <jirislaby@kernel.org>
> Cc: Maxim Levitsky <mlevitsk@redhat.com>
> Cc: Mel Gorman <mgorman@techsingularity.net>
> Cc: Michal Hocko <mhocko@kernel.org>
> Cc: Paolo Bonzini <pbonzini@redhat.com>
> Cc: Thorsten Leemhuis <regressions@leemhuis.info>
> Cc: <stable@vger.kernel.org>
> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
> ---
> 
> 
> --- a/mm/compaction.c~revert-mm-compaction-fix-set-skip-in-fast_find_migrateblock
> +++ a/mm/compaction.c
> @@ -1839,6 +1839,7 @@ static unsigned long fast_find_migratebl
>   					pfn = cc->zone->zone_start_pfn;
>   				cc->fast_search_fail = 0;
>   				found_block = true;
> +				set_pageblock_skip(freepage);
>   				break;
>   			}
>   		}
> _
> 
> Patches currently in -mm which might be from vbabka@suse.cz are
> 
> revert-mm-compaction-fix-set-skip-in-fast_find_migrateblock.patch
> 

thanks,
-- 
js
suse labs


      reply	other threads:[~2023-01-16  5:46 UTC|newest]

Thread overview: 2+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-01-14  4:11 + revert-mm-compaction-fix-set-skip-in-fast_find_migrateblock.patch added to mm-hotfixes-unstable branch Andrew Morton
2023-01-16  5:46 ` Jiri Slaby [this message]

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