https://bugzilla.kernel.org/show_bug.cgi?id=199727 --- Comment #16 from Stefan Hajnoczi (stefanha@xxxxxxxxx) --- On Tue, 8 Mar 2022 at 08:01, <bugzilla-daemon@xxxxxxxxxx> wrote: > > https://bugzilla.kernel.org/show_bug.cgi?id=199727 > > --- Comment #15 from Roland Kletzing (devzero@xxxxxx) --- > yes, i was using cache=none and io_uring also caused issues. > > >aio=threads avoids softlockups because the preadv(2)/pwritev(2)/fdatasync(2) > > syscalls run in worker threads that don't take the QEMU global mutex. > >Therefore vcpu threads can execute even when I/O is stuck in the kernel due > to > >a lock. > > yes, that was a long search/journey to get to this information/params.... > > regarding io_uring - after proxmox enabled it as default, it was taken back > again after some issues had been reported. > > have look at: > https://github.com/proxmox/qemu-server/blob/master/debian/changelog > > maybe it's not ready for primetime yet !? > > -- Proxmox Support Team <support@xxxxxxxxxxx> Fri, 30 Jul 2021 16:53:44 > +0200 > qemu-server (7.0-11) bullseye; urgency=medium > <snip> > * lvm: avoid the use of io_uring for now > <snip> > -- Proxmox Support Team <support@xxxxxxxxxxx> Fri, 23 Jul 2021 11:08:48 > +0200 > qemu-server (7.0-10) bullseye; urgency=medium > <snip> > * avoid using io_uring for drives backed by LVM and configured for > write-back > or write-through cache > <snip> > -- Proxmox Support Team <support@xxxxxxxxxxx> Mon, 05 Jul 2021 20:49:50 > +0200 > qemu-server (7.0-6) bullseye; urgency=medium > <snip> > * For now do not use io_uring for drives backed by Ceph RBD, with KRBD and > write-back or write-through cache enabled, as in that case some > polling/IO > may hang in QEMU 6.0. > <snip> Changelog messages mention cache=writethrough and cache=writeback, which are both problematic because host memory pressure will interfere with guest performance. That is probably not an issue with io_uring per se, just another symptom of using cache=writeback/writethrough in cases where it's inappropriate. If you have trace data showing io_uring_enter(2) hanging with cache=none then Jens Axboe and other io_uring developers may be able to help resolve that. Stefan -- You may reply to this email to add a comment. You are receiving this mail because: You are watching the assignee of the bug.
