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([2601:188:c180:4250:ecbe:130d:668d:951d]) by smtp.gmail.com with ESMTPSA id 6a1803df08f44-7051b90616asm54508526d6.35.2025.07.22.11.41.38 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 22 Jul 2025 11:41:39 -0700 (PDT) From: Waiman Long X-Google-Original-From: Waiman Long Message-ID: <3db01bc9-f6ea-41f7-8cbf-fb33e522694a@redhat.com> Date: Tue, 22 Jul 2025 14:41:38 -0400 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3] memcg: expose socket memory pressure in a cgroup To: Kuniyuki Iwashima , Shakeel Butt Cc: =?UTF-8?Q?Michal_Koutn=C3=BD?= , Daniel Sedlak , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Simon Horman , Jonathan Corbet , Neal Cardwell , David Ahern , Andrew Morton , Yosry Ahmed , linux-mm@kvack.org, netdev@vger.kernel.org, Johannes Weiner , Michal Hocko , Roman Gushchin , Muchun Song , cgroups@vger.kernel.org, Matyas Hurtik References: <20250722071146.48616-1-daniel.sedlak@cdn77.com> In-Reply-To: X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: x1hqwGQIPLiUZHAh8iF6SaOxDS8dRN7J6D2IQ3ENihQ_1753209701 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Rspam-User: X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 257E94000B X-Stat-Signature: f3woxo6aka4uh1bb86pu8xscrox1bpth X-HE-Tag: 1753209703-225020 X-HE-Meta: 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 Hs0424tT 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 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: List-Subscribe: List-Unsubscribe: On 7/22/25 2:27 PM, Kuniyuki Iwashima wrote: > On Tue, Jul 22, 2025 at 10:50 AM Shakeel Butt wrote: >> On Tue, Jul 22, 2025 at 10:57:31AM +0200, Michal Koutný wrote: >>> Hello Daniel. >>> >>> On Tue, Jul 22, 2025 at 09:11:46AM +0200, Daniel Sedlak wrote: >>>> /sys/fs/cgroup/**//memory.net.socket_pressure >>>> >>>> The output value is an integer matching the internal semantics of the >>>> struct mem_cgroup for socket_pressure. It is a periodic re-arm clock, >>>> representing the end of the said socket memory pressure, and once the >>>> clock is re-armed it is set to jiffies + HZ. >>> I don't find it ideal to expose this value in its raw form that is >>> rather an implementation detail. >>> >>> IIUC, the information is possibly valid only during one jiffy interval. >>> How would be the userspace consuming this? >>> >>> I'd consider exposing this as a cummulative counter in memory.stat for >>> simplicity (or possibly cummulative time spent in the pressure >>> condition). >>> >>> Shakeel, how useful is this vmpressure per-cgroup tracking nowadays? I >>> thought it's kind of legacy. >> >> Yes vmpressure is legacy and we should not expose raw underlying number >> to the userspace. How about just 0 or 1 and use >> mem_cgroup_under_socket_pressure() underlying? In future if we change >> the underlying implementation, the output of this interface should be >> consistent. > But this is available only for 1 second, and it will not be useful > except for live debugging ? If the new interface is used mainly for debugging purpose, I will suggest adding the CFTYPE_DEBUG flag so that it will only show up when "cgroup_debug" is specified in the kernel command line. Cheers, Longman