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Wed, 04 Sep 2019 10:07:50 -0700 (PDT) Received: from desktop-bart.svl.corp.google.com ([2620:15c:2cd:202:4308:52a3:24b6:2c60]) by smtp.gmail.com with ESMTPSA id 2sm23516255pfa.43.2019.09.04.10.07.48 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 04 Sep 2019 10:07:49 -0700 (PDT) Subject: Re: [PATCH 1/4] softirq: implement IRQ flood detection mechanism To: Daniel Lezcano , Ming Lei References: <20190827225827.GA5263@ming.t460p> <20190828110633.GC15524@ming.t460p> <20190828135054.GA23861@ming.t460p> <20190903033001.GB23861@ming.t460p> <299fb6b5-d414-2e71-1dd2-9d6e34ee1c79@linaro.org> <20190903063125.GA21022@ming.t460p> <6b88719c-782a-4a63-db9f-bf62734a7874@linaro.org> <20190903072848.GA22170@ming.t460p> From: Bart Van Assche Message-ID: <6f3b6557-1767-8c80-f786-1ea667179b39@acm.org> Date: Wed, 4 Sep 2019 10:07:48 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.8.0 MIME-Version: 1.0 In-Reply-To: Content-Language: en-US X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190904_100751_526065_48D2C09C X-CRM114-Status: GOOD ( 15.44 ) X-BeenThere: linux-nvme@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Keith Busch , Hannes Reinecke , Sagi Grimberg , linux-scsi@vger.kernel.org, Peter Zijlstra , Long Li , John Garry , LKML , linux-nvme@lists.infradead.org, Jens Axboe , Ingo Molnar , Thomas Gleixner , Christoph Hellwig Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Sender: "Linux-nvme" Errors-To: linux-nvme-bounces+linux-nvme=archiver.kernel.org@lists.infradead.org On 9/3/19 12:50 AM, Daniel Lezcano wrote: > On 03/09/2019 09:28, Ming Lei wrote: >> On Tue, Sep 03, 2019 at 08:40:35AM +0200, Daniel Lezcano wrote: >>> It is a scheduler problem then ? >> >> Scheduler can do nothing if the CPU is taken completely by handling >> interrupt & softirq, so seems not a scheduler problem, IMO. > > Why? If there is a irq pressure on one CPU reducing its capacity, the > scheduler will balance the tasks on another CPU, no? Only if CONFIG_IRQ_TIME_ACCOUNTING has been enabled. However, I don't know any Linux distro that enables that option. That's probably because that option introduces two rdtsc() calls in each interrupt. Given the overhead introduced by this option, I don't think this is the solution Ming is looking for. See also irqtime_account_irq() in kernel/sched/cputime.c. Bart. _______________________________________________ Linux-nvme mailing list Linux-nvme@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-nvme