On 2018/12/31 上午2:48, Michael S. Tsirkin wrote:

On Thu, Dec 27, 2018 at 06:04:53PM +0800, Jason Wang wrote:

quoted

On 2018/12/26 下午11:22, Michael S. Tsirkin wrote:

quoted

On Thu, Dec 06, 2018 at 04:17:36PM +0800, Jason Wang wrote:

quoted

On 2018/12/6 上午6:54, Michael S. Tsirkin wrote:

quoted

When use_napi is set, let's enable BQLs.  Note: some of the issues are
similar to wifi.  It's worth considering whether something similar to
commit 36148c2bbfbe ("mac80211: Adjust TSQ pacing shift") might be
benefitial.

I've played a similar patch several days before. The tricky part is the mode
switching between napi and no napi. We should make sure when the packet is
sent and trakced by BQL,  it should be consumed by BQL as well.

I just went over the patch again and I don't understand this comment.
This patch only enabled BQL with tx napi.

Thus there's no mode switching.

What did I miss?

Consider the case:


TX NAPI is disabled:

send N packets

turn TX NAPI on:

get tx interrupt

BQL try to consume those packets when lead WARN for dql.


Thanks

Can one really switch tx napi on and off? How?
While root can change the napi_tx module parameter, I don't think
that has any effect outside device probe time. What did I miss?

We support switch the mode through ethtool recently. See

commit 0c465be183c7c57a26446df6ea96d8676b865f92
Author: Jason Wang [off-list ref]
Date:   Tue Oct 9 10:06:26 2018 +0800

     virtio_net: ethtool tx napi configuration

     Implement ethtool .set_coalesce (-C) and .get_coalesce (-c) handlers.
     Interrupt moderation is currently not supported, so these accept and
     display the default settings of 0 usec and 1 frame.

     Toggle tx napi through setting tx-frames. So as to not interfere
     with possible future interrupt moderation, value 1 means tx napi while
     value 0 means not.

     Only allow the switching when device is down for simplicity.

     Link: https://patchwork.ozlabs.org/patch/948149/
     Suggested-by: Jason Wang [off-list ref]
     Signed-off-by: Willem de Bruijn [off-list ref]
     Signed-off-by: Jason Wang [off-list ref]
     Signed-off-by: David S. Miller [off-list ref]

Thanks

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