There appears to be a hole in the documentation. You know have to set a configuration option to enable tracing:
rbd_tracing = true This will causes librbd.so to dynamically load the tracing module librbd_tp.so (which has linkage to LTTng-UST). On Fri, Jul 15, 2016 at 1:47 PM, Vaibhav Bhembre <vaib...@digitalocean.com> wrote: > I followed the steps mentioned in [1] but somehow I am unable to see any > traces to continue with its step 2. There are no errors seen when performing > operations mentioned in step 1. In my setup I am running lttng commands on > the HV where my VM has the RBD device attached. > > My lttng version is as follows: > > $ lttng --version > lttng (LTTng Trace Control) 2.4.0 - Époque Opaque > r$ lttng-sessiond --version > 2.4.0 > > My uname -r looks like follows: > Linux infra1node71 3.13.0-65-generic #106-Ubuntu SMP Fri Oct 2 22:08:27 UTC > 2015 x86_64 x86_64 x86_64 GNU/Linux > > The kern.log is clear of any apparmor denials as well. > > Would I need to have my librbd linked with lttng-ust by any chance? I don't > see it linked as seen below: > > $ ldd /usr/lib/librbd.so.1.0.0 | grep lttng > $ > > Any idea what I might be missing here to get lttng running successfully? > > [1] http://docs.ceph.com/docs/master/rbd/rbd-replay/ > > > On 07/14, Jason Dillaman wrote: >> >> I would probably be able to resolve the issue fairly quickly if it >> would be possible for you to provide a RBD replay trace from a slow >> and fast mkfs.xfs test run and attach it to the tracker ticket I just >> opened for this issue [1]. You can follow the instructions here [2] >> but would only need to perform steps 1 and 2 (attaching to output from >> step 2 to the ticket). >> >> Thanks, >> >> [1] http://tracker.ceph.com/issues/16689 >> [2] http://docs.ceph.com/docs/master/rbd/rbd-replay/ >> >> On Thu, Jul 14, 2016 at 2:55 PM, Vaibhav Bhembre >> <vaib...@digitalocean.com> wrote: >>> >>> We have been observing this similar behavior. Usually it is the case >>> where >>> we create a new rbd image, expose it into the guest and perform any >>> operation that issues discard to the device. >>> >>> A typical command that's first run on a given device is mkfs, usually >>> with >>> discard on. >>> >>> # time mkfs.xfs -s size=4096 -f /dev/sda >>> meta-data=/dev/sda isize=256 agcount=4, agsize=6553600 >>> blks >>> = sectsz=4096 attr=2, projid32bit=0 >>> data = bsize=4096 blocks=26214400, imaxpct=25 >>> = sunit=0 swidth=0 blks >>> naming =version 2 bsize=4096 ascii-ci=0 >>> log =internal log bsize=4096 blocks=12800, version=2 >>> = sectsz=4096 sunit=1 blks, lazy-count=1 >>> realtime =none extsz=4096 blocks=0, rtextents=0 >>> >>> real 9m10.882s >>> user 0m0.000s >>> sys 0m0.012s >>> >>> When we issue this same command with object-map feature disabled on the >>> image it completes much faster. >>> >>> # time mkfs.xfs -s size=4096 -f /dev/sda >>> meta-data=/dev/sda isize=256 agcount=4, agsize=6553600 >>> blks >>> = sectsz=4096 attr=2, projid32bit=0 >>> data = bsize=4096 blocks=26214400, imaxpct=25 >>> = sunit=0 swidth=0 blks >>> naming =version 2 bsize=4096 ascii-ci=0 >>> log =internal log bsize=4096 blocks=12800, version=2 >>> = sectsz=4096 sunit=1 blks, lazy-count=1 >>> realtime =none extsz=4096 blocks=0, rtextents=0 >>> >>> real 0m1.780s >>> user 0m0.000s >>> sys 0m0.012s >>> >>> Also from what I am seeing the slowness seems to be proportional to the >>> size >>> of the image rather than the amount of data written into it. Issuing mkfs >>> without discard doesn't reproduce this issue. The above values were for >>> 100G >>> rbd image. The 250G takes slightly more than twice the time taken for >>> 100G >>> one. >>> >>> # time mkfs.xfs -s size=4096 -f /dev/sda >>> meta-data=/dev/sda isize=256 agcount=4, agsize=16384000 >>> blks >>> = sectsz=4096 attr=2, projid32bit=0 >>> data = bsize=4096 blocks=65536000, imaxpct=25 >>> = sunit=0 swidth=0 blks >>> naming =version 2 bsize=4096 ascii-ci=0 >>> log =internal log bsize=4096 blocks=32000, version=2 >>> = sectsz=4096 sunit=1 blks, lazy-count=1 >>> realtime =none extsz=4096 blocks=0, rtextents=0 >>> >>> real 22m58.076s >>> user 0m0.000s >>> sys 0m0.024s >>> >>> Let me know if you need any more information regarding this. We would >>> like >>> to enable object-map (and fast-diff) on our images once this gets >>> resolved. >>> >>> >>> On Wed, Jun 22, 2016 at 5:39 PM, Jason Dillaman <jdill...@redhat.com> >>> wrote: >>>> >>>> >>>> I'm not sure why I never received the original list email, so I >>>> apologize for the delay. Is /dev/sda1, from your example, fresh with >>>> no data to actually discard or does it actually have lots of data to >>>> discard? >>>> >>>> Thanks, >>>> >>>> On Wed, Jun 22, 2016 at 1:56 PM, Brian Andrus <band...@redhat.com> >>>> wrote: >>>> > I've created a downstream bug for this same issue. >>>> > >>>> > https://bugzilla.redhat.com/show_bug.cgi?id=1349116 >>>> > >>>> > On Wed, Jun 15, 2016 at 6:23 AM, <l...@jonas-server.de> wrote: >>>> >> >>>> >> Hello guys, >>>> >> >>>> >> We are currently testing Ceph Jewel with object-map feature enabled: >>>> >> >>>> >> rbd image 'disk-22920': >>>> >> size 102400 MB in 25600 objects >>>> >> order 22 (4096 kB objects) >>>> >> block_name_prefix: rbd_data.7cfa2238e1f29 >>>> >> format: 2 >>>> >> features: layering, exclusive-lock, object-map, fast-diff, >>>> >> deep-flatten >>>> >> flags: >>>> >> >>>> >> We use this RBD as disk for a kvm virtual machine with virtio-scsi >>>> >> and >>>> >> discard=unmap. We noticed the following paremeters in /sys/block: >>>> >> >>>> >> # cat /sys/block/sda/queue/discard_* >>>> >> 4096 >>>> >> 1073741824 >>>> >> 0 <- discard_zeroes_data >>>> >> >>>> >> While trying to do a mkfs.ext4 on the disk in VM we noticed a low >>>> >> performance with using discard. >>>> >> >>>> >> mkfs.ext4 -E nodiscard /dev/sda1 - tooks 5 seconds to complete >>>> >> mkfs.ext4 -E discard /dev/sda1 - tooks around 3 monutes >>>> >> >>>> >> When disabling the object-map the mkfs with discard tooks just 5 >>>> >> seconds. >>>> >> >>>> >> Do you have any idea what might cause this issue? >>>> >> >>>> >> Kernel: 4.2.0-35-generic #40~14.04.1-Ubuntu >>>> >> Ceph: 10.2.0 >>>> >> Libvirt: 1.3.1 >>>> >> QEMU: 2.5.0 >>>> >> >>>> >> Thanks! >>>> >> >>>> >> Best regards, >>>> >> Jonas >>>> >> _______________________________________________ >>>> >> ceph-users mailing list >>>> >> ceph-users@lists.ceph.com >>>> >> http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com >>>> > >>>> > >>>> > >>>> > >>>> > -- >>>> > Brian Andrus >>>> > Red Hat, Inc. >>>> > Storage Consultant, Global Storage Practice >>>> > Mobile +1 (530) 903-8487 >>>> > >>>> > >>>> > _______________________________________________ >>>> > ceph-users mailing list >>>> > ceph-users@lists.ceph.com >>>> > http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com >>>> > >>>> >>>> >>>> >>>> -- >>>> Jason >>>> _______________________________________________ >>>> ceph-users mailing list >>>> ceph-users@lists.ceph.com >>>> http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com >>> >>> >>> >> >> >> >> -- >> Jason > > > -- > Vaibhav Bhembre -- Jason _______________________________________________ ceph-users mailing list ceph-users@lists.ceph.com http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
