Re: [ceph-users] command to flush rbd cache?
I don't know the details well; I know the device itself supports the block-device-level cache-flush commands (I know there's a SCSI-specific one but I don't know offhand if there's a device generic one) so the guest OS can, and does, request flushing. I can't remember if there's also a qemu command to prompt the virtual device to flush without telling the guest. On 02/04/2015 11:08 PM, Udo Lembke wrote: > Hi Dan, > I mean qemu-kvm, also librbd. > But how I can kvm told to flush the buffer? > > Udo > > On 05.02.2015 07:59, Dan Mick wrote: >> On 02/04/2015 10:44 PM, Udo Lembke wrote: >>> Hi all, >>> is there any command to flush the rbd cache like the >>> "echo 3 > /proc/sys/vm/drop_caches" for the os cache? >>> >>> Udo >> Do you mean the kernel rbd or librbd? The latter responds to flush >> requests from the hypervisor. The former...I'm not sure it has a >> separate cache. ___ ceph-users mailing list ceph-users@lists.ceph.com http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
Re: [ceph-users] command to flush rbd cache?
Hi Josh, thanks for the info. detach/reattach schould be fine for me, because it's only for performance testing. #2468 would be fine of course. Udo On 05.02.2015 08:02, Josh Durgin wrote: > On 02/05/2015 07:44 AM, Udo Lembke wrote: >> Hi all, >> is there any command to flush the rbd cache like the >> "echo 3 > /proc/sys/vm/drop_caches" for the os cache? > > librbd exposes it as rbd_invalidate_cache(), and qemu uses it > internally, but I don't think you can trigger that via any user-facing > qemu commands. > > Exposing it through the admin socket would be pretty simple though: > > http://tracker.ceph.com/issues/2468 > > You can also just detach and reattach the device to flush the rbd cache. > > Josh ___ ceph-users mailing list ceph-users@lists.ceph.com http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
Re: [ceph-users] command to flush rbd cache?
Hi Dan, I mean qemu-kvm, also librbd. But how I can kvm told to flush the buffer? Udo On 05.02.2015 07:59, Dan Mick wrote: > On 02/04/2015 10:44 PM, Udo Lembke wrote: >> Hi all, >> is there any command to flush the rbd cache like the >> "echo 3 > /proc/sys/vm/drop_caches" for the os cache? >> >> Udo > Do you mean the kernel rbd or librbd? The latter responds to flush > requests from the hypervisor. The former...I'm not sure it has a > separate cache. > ___ ceph-users mailing list ceph-users@lists.ceph.com http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
Re: [ceph-users] command to flush rbd cache?
On 02/05/2015 07:44 AM, Udo Lembke wrote: Hi all, is there any command to flush the rbd cache like the "echo 3 > /proc/sys/vm/drop_caches" for the os cache? librbd exposes it as rbd_invalidate_cache(), and qemu uses it internally, but I don't think you can trigger that via any user-facing qemu commands. Exposing it through the admin socket would be pretty simple though: http://tracker.ceph.com/issues/2468 You can also just detach and reattach the device to flush the rbd cache. Josh ___ ceph-users mailing list ceph-users@lists.ceph.com http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
Re: [ceph-users] command to flush rbd cache?
On 02/04/2015 10:44 PM, Udo Lembke wrote: > Hi all, > is there any command to flush the rbd cache like the > "echo 3 > /proc/sys/vm/drop_caches" for the os cache? > > Udo Do you mean the kernel rbd or librbd? The latter responds to flush requests from the hypervisor. The former...I'm not sure it has a separate cache. -- Dan Mick Red Hat, Inc. Ceph docs: http://ceph.com/docs ___ ceph-users mailing list ceph-users@lists.ceph.com http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
[ceph-users] command to flush rbd cache?
Hi all, is there any command to flush the rbd cache like the "echo 3 > /proc/sys/vm/drop_caches" for the os cache? Udo ___ ceph-users mailing list ceph-users@lists.ceph.com http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
