path: root/async.c
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authorStefan Hajnoczi <stefanha@redhat.com>2016-12-01 19:26:51 +0000
committerStefan Hajnoczi <stefanha@redhat.com>2017-01-03 16:38:50 +0000
commit82a41186941c419afde977f477f19c545b40c1c5 (patch)
tree32d517c6b4b6454814fd54af17bc0b5f7f0ed82c /async.c
parenta7c8215e3bbcdd3b5dbaabfcecf236d4a9880558 (diff)
aio: self-tune polling time
This patch is based on the algorithm for the kvm.ko halt_poll_ns parameter in Linux. The initial polling time is zero. If the event loop is woken up within the maximum polling time it means polling could be effective, so grow polling time. If the event loop is woken up beyond the maximum polling time it means polling is not effective, so shrink polling time. If the event loop makes progress within the current polling time then the sweet spot has been reached. This algorithm adjusts the polling time so it can adapt to variations in workloads. The goal is to reach the sweet spot while also recognizing when polling would hurt more than help. Two new trace events, poll_grow and poll_shrink, are added for observing polling time adjustment. Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com> Reviewed-by: Paolo Bonzini <pbonzini@redhat.com> Message-id: 20161201192652.9509-13-stefanha@redhat.com Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Diffstat (limited to 'async.c')
1 files changed, 3 insertions, 0 deletions
diff --git a/async.c b/async.c
index 29abf40ca7..2960171834 100644
--- a/async.c
+++ b/async.c
@@ -385,7 +385,10 @@ AioContext *aio_context_new(Error **errp)
timerlistgroup_init(&ctx->tlg, aio_timerlist_notify, ctx);
+ ctx->poll_ns = 0;
ctx->poll_max_ns = 0;
+ ctx->poll_grow = 0;
+ ctx->poll_shrink = 0;
return ctx;