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[147.11.105.121]) by smtp.gmail.com with ESMTPSA id f5-20020a0cc305000000b0067f2b6fe775sm3585394qvi.131.2023.12.20.04.38.14 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 20 Dec 2023 04:38:16 -0800 (PST) Date: Wed, 20 Dec 2023 20:38:11 +0800 From: Kevin Hao To: Andrew Morton Cc: linux-mm@kvack.org, "Rafael J. Wysocki" , Pavel Machek Subject: Re: [PATCH v2] mm/khugepaged: Remove redundant try_to_freeze() Message-ID: References: <20231219231753.683171-1-haokexin@gmail.com> <20231219160033.35263ae2818c3e8bd73ae086@linux-foundation.org> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="A9eOepJVKtDYcMPM" Content-Disposition: inline In-Reply-To: <20231219160033.35263ae2818c3e8bd73ae086@linux-foundation.org> X-Rspam-User: X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 5944F4000D X-Stat-Signature: xuja39gra4kbihu4aernsbsqgwoods4m X-HE-Tag: 1703075898-882207 X-HE-Meta: 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 YnMS9ll2 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000003, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: --A9eOepJVKtDYcMPM Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Tue, Dec 19, 2023 at 04:00:33PM -0800, Andrew Morton wrote: > On Wed, 20 Dec 2023 07:17:53 +0800 Kevin Hao wrote: >=20 > > A freezable kernel thread can enter frozen state during freezing by > > either calling try_to_freeze() or using wait_event_freezable() and its > > variants. However, there is no need to use both methods simultaneously. > > The freezable wait variants have been used in khugepaged_wait_work() > > and khugepaged_alloc_sleep(), so remove this redundant > > try_to_freeze(). > >=20 > > ... > > > > --- a/mm/khugepaged.c > > +++ b/mm/khugepaged.c > > @@ -2500,7 +2500,7 @@ static void khugepaged_do_scan(struct collapse_co= ntrol *cc) > > while (true) { > > cond_resched(); > > =20 > > - if (unlikely(kthread_should_stop() || try_to_freeze())) > > + if (unlikely(kthread_should_stop())) > > break; > > =20 > > spin_lock(&khugepaged_mm_lock); >=20 > What are the effects upon worst-case freezing latency? I used the following stress-ng command to generate some memory load on my I= ntel Alder Lake board (24 CPUs, 32G memory). stress-ng --vm 48 --vm-bytes 90% The worst freezing latency is: Freezing user space processes =20 Freezing user space processes completed (elapsed 0.040 seconds) =20 OOM killer disabled. =20 Freezing remaining freezable tasks =20 Freezing remaining freezable tasks completed (elapsed 0.001 seconds) Without the faked memory load, the freezing latency is: Freezing user space processes Freezing user space processes completed (elapsed 0.000 seconds) OOM killer disabled. Freezing remaining freezable tasks Freezing remaining freezable tasks completed (elapsed 0.001 seconds) I didn't see any observable difference whether this patch is applied or not. Thanks, Kevin --A9eOepJVKtDYcMPM Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQEzBAEBCAAdFiEEHc6qFoLCZqgJD98Zk1jtMN6usXEFAmWC4DMACgkQk1jtMN6u sXH7JwgAu5i9ajEj6BSg/peWrOtZuPniIz9rFjL7iKRZY8UwWrx70MzJTYGCaiXl mRbMzUQEO9H9+XxNZIp354KQi90wGphg44JSc+yhTT2YDSxrTU+nZUXyLoQgbd6z cRDFYw0eWwlj8MVyzLZ9GRFGAPTZGmrQ6jV82D+ODxauNuOtZ7IqKmbYJXwjEmOd p76H013LT/xg5Gn4zZZUfFcEbuojj/CjEl4favXxbk9sNekGK7gmBTs1XTr0KqwD k1Hnyhevsvdfu9aUhaGz1bVjZ5eZWzu7sO2OSlSyWOeTdJiHbB0TkJ2uH6goXegr ESRIA12JRnGvwXol0IUM07DE5tI4Lw== =YBAa -----END PGP SIGNATURE----- --A9eOepJVKtDYcMPM--