On Fri, Feb 21, 2020 at 9:40 AM Stefan Hajnoczi <stefa...@redhat.com> wrote: > > The ctx->first_bh list contains all created BHs, including those that > are not scheduled. The list is iterated by the event loop and therefore > has O(n) time complexity with respected to the number of created BHs. > > Rewrite BHs so that only scheduled or deleted BHs are enqueued. > Only BHs that actually require action will be iterated. > > One semantic change is required: qemu_bh_delete() enqueues the BH and > therefore invokes aio_notify(). The > tests/test-aio.c:test_source_bh_delete_from_cb() test case assumed that > g_main_context_iteration(NULL, false) returns false after > qemu_bh_delete() but it now returns true for one iteration. Fix up the > test case. > > This patch makes aio_compute_timeout() and aio_bh_poll() drop from a CPU > profile reported by perf-top(1). Previously they combined to 9% CPU > utilization when AioContext polling is commented out and the guest has 2 > virtio-blk,num-queues=1 and 99 virtio-blk,num-queues=32 devices. > > Signed-off-by: Stefan Hajnoczi <stefa...@redhat.com> > --- > v3: > * Use QSLIST_FOREACH_RCU() and QSLIST_FIRST_RCU() [Paolo]
I forgot to include Paolo's R-b that he gave conditional on making this change: Reviewed-by: Paolo Bonzini <pbonz...@redhat.com>
