From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Subject: Re: problem with fio --client and latency logs References: <1119349874.66202652.1464289871526.JavaMail.zimbra@redhat.com> From: Jens Axboe Message-ID: <57485CF7.2070308@kernel.dk> Date: Fri, 27 May 2016 08:43:03 -0600 MIME-Version: 1.0 In-Reply-To: <1119349874.66202652.1464289871526.JavaMail.zimbra@redhat.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit To: Ben England , fio@vger.kernel.org Cc: Tim Wilkinson , Andrew Theurer , John Harrigan List-ID: On 05/26/2016 01:11 PM, Ben England wrote: > recently I noticed a problem in master branch when fio --client is used. latency logs generated with it have large numbers of "0, 0, 0, 0" records at the end of the file. I have a simple reproducer fio jobfile: > > --------- reproducer.fiojob ---- > [global] > numjobs=1 > directory=/var/tmp > > [shared-files] > rw=randread > write_lat_log=1thr > ioengine=sync > bs=4k # I/O size > filesize=1g # file size > runtime=20 > ------------- > > If you run this job file like this: > > # fio --server --daemonize=/var/run/fiosvr.pid > # fio --client=localhost reproducer.fiojob > > You get the latency log 1thr_clat.1.log with the 0 records at the end. If you run the same job file with: > > # fio reproducer.fiojob > > You don't get the 0 records. This explains why Ceph CBT does not have the problem, for example. > > I bisected fio history using git until I found the first commit that failed: > > ------- > commit 0cba0f919ee6af7dd65df436884336cff9c903f9 > Author: Jens Axboe > Date: Thu Dec 17 14:54:15 2015 -0700 > > client/server: transparent handling of storing compressed logs > > Signed-off-by: Jens Axboe > ------ > > I could use some help figuring out what went wrong at this point, the diffs were complicated but it seemed possible that this commit was related to my problem. I have a good idea what this might be, I'll take a look at it. -- Jens Axboe