From mboxrd@z Thu Jan 1 00:00:00 1970 From: axboe@kernel.dk (Jens Axboe) Date: Tue, 20 Feb 2018 12:37:07 -1000 Subject: [PATCH] blk: optimization for classic polling In-Reply-To: <20180220132137.GG25314@hirez.programming.kicks-ass.net> References: <3578876466-3733-1-git-send-email-nj.shetty@samsung.com> <20180220132137.GG25314@hirez.programming.kicks-ass.net> Message-ID: <35a2d52e-dd40-d130-85d9-5f3ffe0d28af@kernel.dk> On 2/20/18 3:21 AM, Peter Zijlstra wrote: > On Sun, May 30, 2083@09:51:06AM +0530, Nitesh Shetty wrote: >> This removes the dependency on interrupts to wake up task. Set task >> state as TASK_RUNNING, if need_resched() returns true, >> while polling for IO completion. >> Earlier, polling task used to sleep, relying on interrupt to wake it up. >> This made some IO take very long when interrupt-coalescing is enabled in >> NVMe. > > This is a horrible Changelog.. it does not in fact explain why the patch > works or is correct. Yeah, that should have been improved. > Also, set_current_state(TASK_RUNNING) is dodgy (similarly in > __blk_mq_poll), why do you need that memory barrier? I pointed that out in the review, and v2 fixed it. v2 is the one that got merged. -- Jens Axboe