From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Subject: Re: RBD client cache References: From: Jens Axboe Message-ID: <564E318C.3060602@kernel.dk> Date: Thu, 19 Nov 2015 13:31:08 -0700 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit To: Jens Rosenboom , fio@vger.kernel.org List-ID: On 11/19/2015 08:37 AM, Jens Rosenboom wrote: > A couple of releases ago, ceph has changed the default value for > > rbd cache writethrough until flush > > from false to true. As the fio rbd backend currently does not emit the > necessary fsync to trigger writeback mode, this implies that tests > will run in writethrough, possibly giving a significantly reduced > performance when compared to other clients, e.g. when running fio > within a qemu-based instance accessing the same RBD volume. > > Would it make sense for fio to simply issue a rbd_flush after each > rbd_open at https://github.com/axboe/fio/blob/master/engines/rbd.c#L138 > ? Or do you think that this would need a dedicated flag to be enabled? I'd probably make that an rbd engine option, ala flush_on_open or something like that. -- Jens Axboe