From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Darrick J. Wong" Subject: Re: [PATCH] block: add iostat counters for flush requests Date: Thu, 21 Nov 2019 08:04:30 -0800 Message-ID: <20191121160430.GJ6211@magnolia> References: <157433282607.7928.5202409984272248322.stgit@buzz> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org To: Jens Axboe Cc: Konstantin Khlebnikov , linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-api@vger.kernel.org, Dmitry Monakhov List-Id: linux-api@vger.kernel.org On Thu, Nov 21, 2019 at 08:56:14AM -0700, Jens Axboe wrote: > On 11/21/19 3:40 AM, Konstantin Khlebnikov wrote: > > Requests that triggers flushing volatile writeback cache to disk (barriers) > > have significant effect to overall performance. > > > > Block layer has sophisticated engine for combining several flush requests > > into one. But there is no statistics for actual flushes executed by disk. > > Requests which trigger flushes usually are barriers - zero-size writes. > > > > This patch adds two iostat counters into /sys/class/block/$dev/stat and > > /proc/diskstats - count of completed flush requests and their total time. > > This makes sense to me, and the "recent" discard addition already proved > that we're fine extending with more fields. Unless folks object, I'd be > happy to queue this up for 5.5. Looks like a good addition to /me... :) --D > -- > Jens Axboe >