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Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Simon Horman , Jonathan Corbet , Neal Cardwell , Kuniyuki Iwashima , 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, Tejun Heo , =?UTF-8?Q?Michal_Koutn=C3=BD?= , Matyas Hurtik References: <20250805064429.77876-1-daniel.sedlak@cdn77.com> Content-Language: en-US From: Daniel Sedlak In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-CTCH: RefID="str=0001.0A00210C.689482D2.0077,ss=1,re=0.000,recu=0.000,reip=0.000,cl=1,cld=1,fgs=0"; Spam="Unknown"; VOD="Unknown" X-Rspam-User: X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: A473714000A X-Stat-Signature: 3ff85krgibfztgiywg86jcrqfhd3bn4j X-HE-Tag: 1754563353-333438 X-HE-Meta: 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 2Ua9pAHn Uxjwk9xjjk0Zp5esjslDWIdg3sDY3lcrIi9dA6xhSr4eyWnpHjASdTl0l2Hz2leA48MzHFD/VgjjWHQMKl0fiwNSZxgtkLlB/17vQWqnVJgEgf7lykyrpGoubNmllw7/zNfrRRHVEfVA5yDhFGBVjaNXcjCLVHLOzmZGO0pHorQCq/MWutt/IJc6M7QrSO1juNS1VavstC7SIhH+Q0STeBELJ9ljTe03WFmOjYdcVx+ZnPUcCODI4LzH/+j0H8Bm/Za+jQAUHYILjigk= 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 8/6/25 1:02 AM, Shakeel Butt wrote: > On Tue, Aug 05, 2025 at 08:44:29AM +0200, Daniel Sedlak wrote: >> This patch is a result of our long-standing debug sessions, where it all >> started as "networking is slow", and TCP network throughput suddenly >> dropped from tens of Gbps to few Mbps, and we could not see anything in >> the kernel log or netstat counters. >> >> Currently, we have two memory pressure counters for TCP sockets [1], >> which we manipulate only when the memory pressure is signalled through >> the proto struct [2]. However, the memory pressure can also be signaled >> through the cgroup memory subsystem, which we do not reflect in the >> netstat counters. In the end, when the cgroup memory subsystem signals >> that it is under pressure, we silently reduce the advertised TCP window >> with tcp_adjust_rcv_ssthresh() to 4*advmss, which causes a significant >> throughput reduction. >> >> Keep in mind that when the cgroup memory subsystem signals the socket >> memory pressure, it affects all sockets used in that cgroup. >> >> This patch exposes a new file for each cgroup in sysfs which signals >> the cgroup socket memory pressure. The file is accessible in >> the following path. >> >> /sys/fs/cgroup/**//memory.net.socket_pressure > > let's keep the name concise. Maybe memory.net.pressure? > Sure, I can rename it for v5. Thanks! Daniel