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AJvYcCVAWjtgI0D0qXLT/uVBSbJNTHUdZsFIcakKp6zGa6KmAhIPfrhB+zxljKVGv+ny03OxUe1SAkzQ@vger.kernel.org, AJvYcCWYpjXm/o3jASBgXkFF22C2qeh/zymvW5/QNWXAxxQxTXJUOKF3LZzyyeNt1V85tZni+srkGI1VQVA4rkA5@vger.kernel.org X-Gm-Message-State: AOJu0YzIARXTRETztdSL+a+GWq7dS67gxesBxYdWqAmwBZENMR0ReJ0W eeJo1kkIKe4n3rSY9fln7To47dadz2+rZN21eZMfiIEvFbMbjrPRrY1YdXgLdamfTvwMEXaaKrj up9xW2fgaURsfbUAVzbb0iMC35b9i24Q= X-Gm-Gg: ASbGnctuxbkggS7UiuVJt52fRqbL1g4VL6O8diMMfxij2FiTBhIbA7m84tx4pojT27Z NGTZLJKziXY9uJ1pC2U8KMy6yCO3MJbF40ChqQufVkqrYOW7rFvIYRC/3Zq8PmwJxW9STe9rHSm 4WRJYM6zWPuCP3R05vMZs9DFNBxsoIH7fEnMVc/fRdUsvcQw9UXoVrIN4= X-Google-Smtp-Source: AGHT+IEmn7LOIXOqzn94ygtrgYOdYuISQJpF/KL7y3Q6iZwh20kDfRclQ7Wn9Fm0BTI+5nzBDZcxtCzZgBc3XbPO7+w= X-Received: by 2002:ad4:4ea9:0:b0:6f8:aa6f:438b with SMTP id 6a1803df08f44-6fa9cfff0b8mr227915346d6.3.1748398417228; Tue, 27 May 2025 19:13:37 -0700 (PDT) Precedence: bulk X-Mailing-List: cgroups@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 References: <20250511030800.1900-1-laoar.shao@gmail.com> <20250511030800.1900-3-laoar.shao@gmail.com> In-Reply-To: From: Yafang Shao Date: Wed, 28 May 2025 10:13:01 +0800 X-Gm-Features: AX0GCFv7oMXfKN2u6YrYssepdLwylVhGKiw41GScgqmD-kM6FEB8melzxvcy-FI Message-ID: Subject: Re: [PATCH v9 2/2] sched: Annotate sched_clock_irqtime with __read_mostly To: =?UTF-8?Q?Michal_Koutn=C3=BD?= Cc: mingo@redhat.com, peterz@infradead.org, hannes@cmpxchg.org, juri.lelli@redhat.com, vincent.guittot@linaro.org, dietmar.eggemann@arm.com, rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de, vschneid@redhat.com, surenb@google.com, linux-kernel@vger.kernel.org, cgroups@vger.kernel.org, lkp@intel.com, Eric Dumazet Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On Tue, May 27, 2025 at 11:33=E2=80=AFPM Michal Koutn=C3=BD wrote: > > On Sun, May 11, 2025 at 11:08:00AM +0800, Yafang Shao wrote: > > Eric reported an issue [0] as follows, > > : rebalance_domains() can attempt to change sched_balance_running > > : more than 350,000 times per second on our servers. > > > > : If sched_clock_irqtime and sched_balance_running share the > > : same cache line, we see a very high cost on hosts with 480 threads > > : dealing with many interrupts. > > I'd say this patch could be independent from the "series". I will send it separately. > > > While the rebalance_domains() issue has been resolved [1], we should > > proactively annotate sched_clock_irqtime with __read_mostly to prevent > > potential cacheline false sharing. This optimization is particularly > > justified since sched_clock_irqtime is only modified during TSC instabi= lity > > events. > > > > Link: https://lore.kernel.org/all/20250423174634.3009657-1-edumazet@goo= gle.com/ [0] > > Link: https://lore.kernel.org/all/20250416035823.1846307-1-tim.c.chen@l= inux.intel.com/ [1] > > > > Reported-by: Eric Dumazet > > Debugged-by: Eric Dumazet > > Signed-off-by: Yafang Shao > > Cc: Eric Dumazet > > I can say > Reviewed-by: Michal Koutn=C3=BD Thanks for the review. > > but it'd be good to have also Tested-by: wrt the cache traffic > reduction. --=20 Regards Yafang