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Thu, 17 Apr 2025 05:33:08 -0700 (PDT) Message-ID: <89994086-e750-4dd8-9931-f2777890ab97@kernel.dk> Date: Thu, 17 Apr 2025 06:33:08 -0600 Precedence: bulk X-Mailing-List: linux-block@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] block: blk-rq-qos: guard rq-qos helpers by static key To: Yu Kuai , "linux-block@vger.kernel.org" , "yukuai (C)" References: <207f1ba2-125c-66b1-a5e5-d336f3705ad9@huaweicloud.com> Content-Language: en-US From: Jens Axboe In-Reply-To: <207f1ba2-125c-66b1-a5e5-d336f3705ad9@huaweicloud.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit On 4/17/25 5:08 AM, Yu Kuai wrote: > 在 2025/04/15 22:52, Jens Axboe 写道: >> Even if blk-rq-qos isn't used or configured, dipping into the queue to >> fetch ->rq_qos is a noticeable slowdown and visible in profiles. Add an >> unlikely static key around blk-rq-qos, to avoid fetching this cacheline >> if blk-iolatency or blk-wbt isn't configured or used. >> >> Signed-off-by: Jens Axboe >> >> --- >> > LGTM > > Reviewed-by: Yu Kuai > > BTW, do we want the same thing for q->td? We may want to do that - I haven't seen that in the hot path yet, but I also think I may have it configured out... -- Jens Axboe