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bh=JMuTmf0F+QOiaF6t8tr3QA/L27lx/sQSTLa4V7SznDY=; b=LMYMDQKMZ7Qo4VvbYjlK3lmM/OKd2359yCXU2EFKolo15/dL8xBx9RP656ePv9oxTz6Y6w NEgXosiAyJ9ADKeU2+xveaIYxq6bzCVR6VFy6q0dHg/X81EQgsU4m6E7vbDNtZCALw8XTg tWyvo1svOgHpf077fXJ4vguWReYVanU= Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by imap2.suse-dmz.suse.de (Postfix) with ESMTPS id 0983C13349; Thu, 2 Mar 2023 17:39:47 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap2.suse-dmz.suse.de with ESMTPSA id njL0OmPfAGReTQAAMHmgww (envelope-from ); Thu, 02 Mar 2023 17:39:47 +0000 Date: Thu, 2 Mar 2023 18:39:47 +0100 From: Michal Hocko To: Suren Baghdasaryan Cc: tj@kernel.org, hannes@cmpxchg.org, lizefan.x@bytedance.com, peterz@infradead.org, johunt@akamai.com, keescook@chromium.org, quic_sudaraja@quicinc.com, cgroups@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 1/1] psi: remove 500ms min window size limitation for triggers Message-ID: References: <20230301193403.1507484-1-surenb@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspam-User: X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: BC35414001D X-Stat-Signature: 14syyanrsdxtgmr19yghh95i8px41hr6 X-HE-Tag: 1677778789-617820 X-HE-Meta: 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 qB0nCYtD jvW3rW4ZQ3zlaICRPJBY0xPgZ+5oOMfEoXuqYVjTCXaPhkwWBfnx6nYvByOohEUvGQ4lraPGjFkaS4zufx+ERbNNkeMC6TxQ3cnLj/IJmojbJUAcahCFqKCgJPV3jS0PPVYPAe4+W9ExD8NZhph63G262vayiANH2rENANwmYNAJD9WMrks64n67gGENsiIudhEEf8BRSPExDjNw6dG0Egl1/kJvGgEBicOW/Rkla+FD/OjrGbCLi2XD2OeLuCPOcpkQPOiI7oqjJWmIt89EQmTnTrVTJRc8SSWydtHr6bXY3AbCCKMMZH/pQ8RKcRvJYMxps4izvDMXmgUaXVwgnFc6IyUr0KSFETW8U7Jz1herCfp9BW3rlAbRI5Q== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Thu 02-03-23 08:08:38, Suren Baghdasaryan wrote: > On Thu, Mar 2, 2023 at 5:58 AM Michal Hocko wrote: > > > > On Wed 01-03-23 11:34:03, Suren Baghdasaryan wrote: > > > Current 500ms min window size for psi triggers limits polling interval > > > to 50ms to prevent polling threads from using too much cpu bandwidth by > > > polling too frequently. However the number of cgroups with triggers is > > > unlimited, so this protection can be defeated by creating multiple > > > cgroups with psi triggers (triggers in each cgroup are served by a single > > > "psimon" kernel thread). > > > Instead of limiting min polling period, which also limits the latency of > > > psi events, it's better to limit psi trigger creation to authorized users > > > only, like we do for system-wide psi triggers (/proc/pressure/* files can > > > be written only by processes with CAP_SYS_RESOURCE capability). This also > > > makes access rules for cgroup psi files consistent with system-wide ones. > > > Add a CAP_SYS_RESOURCE capability check for cgroup psi file writers and > > > remove the psi window min size limitation. > > > > > > Suggested-by: Sudarshan Rajagopalan > > > Link: https://lore.kernel.org/all/cover.1676067791.git.quic_sudaraja@quicinc.com/ > > > Signed-off-by: Suren Baghdasaryan > > > > Acked-by: Michal Hocko > > > > with this to fix > > [...] > > > @@ -1278,8 +1277,7 @@ struct psi_trigger *psi_trigger_create(struct psi_group *group, > > > if (state >= PSI_NONIDLE) > > > return ERR_PTR(-EINVAL); > > > > > > - if (window_us < WINDOW_MIN_US || > > > - window_us > WINDOW_MAX_US) > > > + if (window_us <= 0 || window_us > WINDOW_MAX_US) > > > return ERR_PTR(-EINVAL); > > > > window_us is u32 sp the check for <= 0 doesn't make any sense. > > Completely missed that. Will change to == 0 and post the new version. I was about to asky check for 0 actually matters but maybe a future extension might give it a special meaning so it is likely a good idea to EINVAL on 0 now. You can keep my ack on that change -- Michal Hocko SUSE Labs