On Wed, Aug 23, 2023 at 4:12 PM Ard Biesheuvel <a...@kernel.org> wrote: > > On Wed, 23 Aug 2023 at 13:08, Gerd Hoffmann <kra...@redhat.com> wrote: > > > > On Tue, Aug 22, 2023 at 09:57:12AM +0200, Ard Biesheuvel wrote: > > > On Tue, 22 Aug 2023 at 08:25, Gerd Hoffmann <kra...@redhat.com> wrote: > > > > > > > > Looks good to me. > > > > > > > > What is the status? Merged? Or waiting for testing still? If so I can > > > > create a test build with the patch and ask our QE department to check > > > > it. > > > > > > > > > > Still waiting for testing, so yes, please test. > > > > Hmm, QE reports back it slows down the boot alot. No boot hangs yet > > with 12 test runs so far, which isn't that much for a reproduce rate > > below 20% ... > > > > https://bugzilla.redhat.com//show_bug.cgi?id=2211060#c28 > > > > So I guess we go with the TPL version for the coming stable tag and > > leave any improvements for later ... > > > > Yeah, this was not going to make the stable tag in any case. > > The boot speed regression seems odd, though - this is effectively UP > code so there shouldn't be any contention, the only thing this patch > does is ensure that the critical section is restarted if it was > interrupted
FWIW: Given completely correct logic, straightforward logic, a lock cmpxchg is much slower(3-4x) than an a non-lock cmpxchg, which itself is around 2x as slow as a regular relaxed load + store. See https://gist.github.com/heatd/49c9be23ccb1f4ad8dfeac231da2647a for a nice fun test benchmark. HOWEVER, given this is likely in IO paths, I would *really* not expect this to make a difference, right? Even virtio drivers will themselves trap with a VMEXIT whenever you touch a hardware register... Gerd, could you folks get a perf kvm (perf-kvm(1)) recording out of that OVMF build? Assuming you can get that thing to work, that is, personally it mysteriously stopped working 6 years ago for me :) -- Pedro -=-=-=-=-=-=-=-=-=-=-=- Groups.io Links: You receive all messages sent to this group. View/Reply Online (#107988): https://edk2.groups.io/g/devel/message/107988 Mute This Topic: https://groups.io/mt/100256049/21656 Group Owner: devel+ow...@edk2.groups.io Unsubscribe: https://edk2.groups.io/g/devel/unsub [arch...@mail-archive.com] -=-=-=-=-=-=-=-=-=-=-=-
