From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Date: Wed, 2 Nov 2016 15:59:48 +0100 From: Christoph Hellwig To: Jens Axboe Cc: Christoph Hellwig , axboe@kernel.dk, linux-kernel@vger.kernel.org, linux-block@vger.kernel.org Subject: Re: [PATCH 1/4] block: add scalable completion tracking of requests Message-ID: <20161102145948.GA14307@lst.de> References: <1478034325-28232-1-git-send-email-axboe@fb.com> <1478034325-28232-2-git-send-email-axboe@fb.com> <20161102145239.GB13964@lst.de> <1954bf49-eeff-0b16-3cf9-7d7d02f25562@fb.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <1954bf49-eeff-0b16-3cf9-7d7d02f25562@fb.com> List-ID: On Wed, Nov 02, 2016 at 08:55:16AM -0600, Jens Axboe wrote: > On 11/02/2016 08:52 AM, Christoph Hellwig wrote: >> On Tue, Nov 01, 2016 at 03:05:22PM -0600, Jens Axboe wrote: >>> For legacy block, we simply track them in the request queue. For >>> blk-mq, we track them on a per-sw queue basis, which we can then >>> sum up through the hardware queues and finally to a per device >>> state. >> >> what is the use case for the legacy request tracking? > > Buffered writeback code uses the same base. Additionally, it could > replace some user space tracking for latency outliers that people are > currently running. Ok.