Re: [PATCH net-next v5 0/4] net: vhost: improve performance when enable busyloop

On 2018年07月12日 11:34, Michael S. Tsirkin wrote:

On Thu, Jul 12, 2018 at 11:26:12AM +0800, Jason Wang wrote:

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On 2018年07月11日 19:59, Michael S. Tsirkin wrote:

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On Wed, Jul 11, 2018 at 01:12:59PM +0800, Jason Wang wrote:

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On 2018年07月11日 11:49, Tonghao Zhang wrote:

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On Wed, Jul 11, 2018 at 10:56 AM Jason Wang [off-list ref] wrote:

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On 2018年07月04日 12:31, xiangxia.m.yue@gmail.com wrote:

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From: Tonghao Zhang <redacted>

This patches improve the guest receive and transmit performance.
On the handle_tx side, we poll the sock receive queue at the same time.
handle_rx do that in the same way.

For more performance report, see patch 4.

v4 -> v5:
fix some issues

v3 -> v4:
fix some issues

v2 -> v3:
This patches are splited from previous big patch:
http://patchwork.ozlabs.org/patch/934673/

Tonghao Zhang (4):
      vhost: lock the vqs one by one
      net: vhost: replace magic number of lock annotation
      net: vhost: factor out busy polling logic to vhost_net_busy_poll()
      net: vhost: add rx busy polling in tx path

     drivers/vhost/net.c   | 108 ++++++++++++++++++++++++++++----------------------
     drivers/vhost/vhost.c |  24 ++++-------
     2 files changed, 67 insertions(+), 65 deletions(-)

Hi, any progress on the new version?

I plan to send a new series of packed virtqueue support of vhost. If you
plan to send it soon, I can wait. Otherwise, I will send my series.

I rebase the codes. and find there is no improvement anymore, the
patches of  makita  may solve the problem. jason you may send your
patches, and I will do some research on busypoll.

I see. Maybe you can try some bi-directional traffic.

Btw, lots of optimizations could be done for busy polling. E.g integrating
with host NAPI busy polling or a 100% busy polling vhost_net. You're welcome
to work or propose new ideas.

Thanks

It seems clear we do need adaptive polling.

Yes.

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   The difficulty with NAPI
polling is it can't access guest memory easily. But maybe
get_user_pages on the polled memory+NAPI polling can work.

You mean something like zerocopy? Looks like we can do busy polling without
it. I mean something like https://patchwork.kernel.org/patch/8707511/.

Thanks

How does this patch work? vhost_vq_avail_empty can sleep,
you are calling it within an rcu read side critical section.

Ok, I get your meaning. I have patches to access vring through 
get_user_pages + vmap() which should help here. (And it increase PPS 
about 10%-20%).

That's not the only problem btw, another one is that the
CPU time spent polling isn't accounted with the VM.

Yes, but it's not the 'issue' of this patch. And I believe cgroup can help?

Thanks

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Thanks

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