From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Subject: Re: [PATCH] blk-throttle: ignore discard request size To: Shaohua Li , linux-block@vger.kernel.org Cc: Kernel-team@fb.com References: <67ffcf14c2d15622b84c60a493b590dd81a07f51.1503068984.git.shli@fb.com> From: Jens Axboe Message-ID: Date: Fri, 18 Aug 2017 09:35:01 -0600 MIME-Version: 1.0 In-Reply-To: <67ffcf14c2d15622b84c60a493b590dd81a07f51.1503068984.git.shli@fb.com> Content-Type: text/plain; charset=utf-8 List-ID: On 08/18/2017 09:13 AM, Shaohua Li wrote: > discard request usually is very big and easily use all bandwidth budget > of a cgroup. discard request size doesn't really mean the size of data > written, so it doesn't make sense to account it into bandwidth budget. > This patch ignores discard requests size. It makes sense to account > discard request into iops budget though. Some (most) devices to touch media for a discard operation, but the cost tends to be fairly constant and independent of discard size. Would it make sense to just treat it as a constant cost? Zero cost seems wrong. -- Jens Axboe