Re: [PULL 11/23] Revert "graph-lock: Disable locking for now"
On Jul 10 14:40, Kevin Wolf wrote: > Am 10.07.2023 um 14:22 hat Klaus Jensen geschrieben: > > On Jun 28 16:15, Kevin Wolf wrote: > > > Now that bdrv_graph_wrlock() temporarily drops the AioContext lock that > > > its caller holds, it can poll without causing deadlocks. We can now > > > re-enable graph locking. > > > > > > This reverts commit ad128dff0bf4b6f971d05eb4335a627883a19c1d. > > > > > > > I'm seeing a pretty major performance regression on iothread-enabled > > virtio-blk (and on some on-going iothread hw/nvme work) with this > > applied. Something like ~300k iops prior to this vs ~200k after on my > > set up. On master, virtio-blk is currently faster without an iothread > > (~215k) than with (~200k). > > > > I bisected the change in iops to this revert. > > Is CONFIG_DEBUG_GRAPH_LOCK enabled in your build? If so, this is > expected to cost some performance. If not, we need to take a look at > what else is causing the regression. > > Kevin Argh. Doh. Yes, was enabled and made QUITE the difference. Sorry for the noise. Thanks! signature.asc Description: PGP signature
Re: [PULL 11/23] Revert "graph-lock: Disable locking for now"
Am 10.07.2023 um 14:22 hat Klaus Jensen geschrieben: > On Jun 28 16:15, Kevin Wolf wrote: > > Now that bdrv_graph_wrlock() temporarily drops the AioContext lock that > > its caller holds, it can poll without causing deadlocks. We can now > > re-enable graph locking. > > > > This reverts commit ad128dff0bf4b6f971d05eb4335a627883a19c1d. > > > > I'm seeing a pretty major performance regression on iothread-enabled > virtio-blk (and on some on-going iothread hw/nvme work) with this > applied. Something like ~300k iops prior to this vs ~200k after on my > set up. On master, virtio-blk is currently faster without an iothread > (~215k) than with (~200k). > > I bisected the change in iops to this revert. Is CONFIG_DEBUG_GRAPH_LOCK enabled in your build? If so, this is expected to cost some performance. If not, we need to take a look at what else is causing the regression. Kevin signature.asc Description: PGP signature
Re: [PULL 11/23] Revert "graph-lock: Disable locking for now"
On Jun 28 16:15, Kevin Wolf wrote: > Now that bdrv_graph_wrlock() temporarily drops the AioContext lock that > its caller holds, it can poll without causing deadlocks. We can now > re-enable graph locking. > > This reverts commit ad128dff0bf4b6f971d05eb4335a627883a19c1d. > I'm seeing a pretty major performance regression on iothread-enabled virtio-blk (and on some on-going iothread hw/nvme work) with this applied. Something like ~300k iops prior to this vs ~200k after on my set up. On master, virtio-blk is currently faster without an iothread (~215k) than with (~200k). I bisected the change in iops to this revert. signature.asc Description: PGP signature
