On Tue, Nov 23, 2010 at 10:13:43AM +0800, lidong chen wrote:
> I test the performance between per-vhost kthread disable and enable.
>
> Test method:
> Send the same traffic load between per-vhost kthread disable and
> enable, and compare the cpu rate of host os.
> I run five vm on kvm, each of them have five nic.
> the vhost version which per-vhost kthread disable we used is rhel6
> beta 2(2.6.32.60).
> the vhost version which per-vhost kthread enable we used is rhel6 (2.6.32-71).
>
> Test result:
> with per-vhost kthread disable, the cpu rate of host os is 110%.
> with per-vhost kthread enable, the cpu rate of host os is 130%.
Does it help if we schedule out the thread once we've passed
once over all vqs?
Something like this:
diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
index 1b0a20d..256e915 100644
--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c
@@ -175,6 +175,7 @@ static int vhost_worker(void *data)
struct vhost_dev *dev = data;
struct vhost_work *work = NULL;
unsigned uninitialized_var(seq);
+ int n = 0;
use_mm(dev->mm);
@@ -206,9 +207,11 @@ static int vhost_worker(void *data)
if (work) {
__set_current_state(TASK_RUNNING);
work->fn(work);
- } else
- schedule();
-
+ if (likely(++n < dev->nvqs))
+ continue;
+ }
+ schedule();
+ n = 0;
}
unuse_mm(dev->mm);
return 0;
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