Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
Date:   Wed, 19 May 2021 20:08:01 +0100
From:   Aaron Tomlin <atomlin@redhat.com>
To:     Vlastimil Babka <vbabka@suse.cz>
Cc:     linux-mm@kvack.org, akpm@linux-foundation.org, mhocko@suse.com,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH] mm/page_alloc: bail out on fatal signal during
 reclaim/compaction retry attempt
Message-ID: <20210519190801.t7fqdtixqmobqsps@ava.usersys.com>
References: <20210519130609.r3ml6ohb2qsrfq2t@ava.usersys.com>
 <20210519145014.3220164-1-atomlin@redhat.com>
 <076e1c68-b4a2-26ea-9538-d88e6da800cc@suse.cz>
MIME-Version: 1.0
Content-Type: multipart/signed; micalg=pgp-sha256;
        protocol="application/pgp-signature"; boundary="kaijdhkoyswy6ze5"
Content-Disposition: inline
In-Reply-To: <076e1c68-b4a2-26ea-9538-d88e6da800cc@suse.cz>
Precedence: bulk


--kaijdhkoyswy6ze5
Content-Type: text/plain; charset=utf-8
Content-Disposition: inline
Content-Transfer-Encoding: quoted-printable

On Wed 2021-05-19 17:22 +0200, Vlastimil Babka wrote:
> Hm, indeed, if fatal_signal_pending() is true then try_to_compact_pages()=
 will
> bail out in the for-each-zone loop after trying a single zone and if that=
 zone
> keeps returning COMPACT_SKIPPED, things can get stuck.
> And direct reclaim might see compaction_ready() for another zone and retu=
rn 1,
> faking the progress.

Indeed.

> So your patch seems to be solving the issue. But maybe we should just do =
the
> test at the beginning of should_compact_retry() and not specific to
> compaction_needs_reclaim() - if there's a fatal signal, there will be no
> compaction happening, so we should just say not to retry.

Fair enough - I will post a v2.

> I suppose if the patch fixes your situation where fatal_signal_pending() =
was
> true, there's hopefully not a more general problem with the retry logic?

At the present time, not to my knowledge. That being said, I will continue
to review the relevant source code further.


Kind regards,

--=20
Aaron Tomlin

--kaijdhkoyswy6ze5
Content-Type: application/pgp-signature; name="signature.asc"

-----BEGIN PGP SIGNATURE-----
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=wzHG
-----END PGP SIGNATURE-----

--kaijdhkoyswy6ze5--