On Fri, Jan 31, 2014 at 9:52 PM, Arne Wiebalck <Arne.Wiebalck@xxxxxxx> wrote: > Hi, > > We observe that we can easily create slow requests with a simple dd on > CephFS: > > --> > [root@p05153026953834 dd]# dd if=/dev/zero of=xxx bs=4M count=1000 > 1000+0 records in > 1000+0 records out > 4194304000 bytes (4.2 GB) copied, 4.27824 s, 980 MB/s > > ceph -w: > 2014-01-31 14:28:44.009543 osd.450 [WRN] 1 slow requests, 1 included below; > oldest blocked for > 31.088950 secs > 2014-01-31 14:28:44.009676 osd.450 [WRN] slow request 31.088950 seconds old, > received at 2014-01-31 14:28:12.920423: osd_op(client.16735018.1:22493091 > 100000352b3.000002e9 [write 0~4194304,startsync 0~0] 0.518f2eef snapc 1=[] > e32400) v4 currently waiting for subops from [87,1190] > <--- > > From what we see, the OSDs are not busy, so we suspect that it is the client > starting all requests, > but then the requests take longer than 30 secs to finish writing, i.e. > flushing the client-side buffers. > > Is our understanding correct? > Do these slow requests have an impact on requests from other clients, i.e. > some OSD resources > consumed by these clients? No. The slow request calculation doesn't take the time when client sent the request into consideration, it only checks the time when OSD received the request. > > The setup is: > Client: kernel 3.13.0, 1GbE > MDS Emperor 0.72.2 > OSDs Dumpling 0.67.5 > > Thanks! > Dan & Arne > > > -- > Arne Wiebalck > CERN IT > > > _______________________________________________ > ceph-users mailing list > ceph-users@xxxxxxxxxxxxxx > http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com > _______________________________________________ ceph-users mailing list ceph-users@xxxxxxxxxxxxxx http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
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