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([2001:16b8:48a0:3f00:587:bfc1:3ea4:c2f6]) by smtp.gmail.com with ESMTPSA id k11sm7603742wrd.23.2020.07.09.11.48.08 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 09 Jul 2020 11:48:08 -0700 (PDT) Subject: Re: [PATCH RFC 4/5] block: add a statistic table for io latency From: Guoqing Jiang To: Ming Lei Cc: axboe@kernel.dk, linux-block@vger.kernel.org, Florian-Ewald Mueller References: <20200708075819.4531-1-guoqing.jiang@cloud.ionos.com> <20200708075819.4531-5-guoqing.jiang@cloud.ionos.com> <20200708132958.GC3340386@T590> Message-ID: Date: Thu, 9 Jul 2020 20:48:08 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.8.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Content-Language: en-US Sender: linux-block-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org Hi Ming, On 7/8/20 4:06 PM, Guoqing Jiang wrote: > On 7/8/20 4:02 PM, Guoqing Jiang wrote: >>> Hi Guoqing, >>> >>> I believe it isn't hard to write a ebpf based script(bcc or >>> bpftrace) to >>> collect this kind of performance data, so looks not necessary to do it >>> in kernel. >> >> Hi Ming, >> >> Sorry, I don't know well about bcc or bpftrace, but I assume they >> need to >> read the latency value from somewhere inside kernel. Could you point >> how can I get the latency value? Thanks in advance! > > Hmm, I suppose biolatency is suitable for track latency, will look > into it. I think biolatency can't trace data if it is not running, also seems no place inside kernel have recorded such information for ebpf to read, correct me if my understanding is wrong. And as cloud provider,we would like to know data when necessary instead of collect data by keep script running because it is expensive than just read node IMHO. Thanks, Guoqing