On 6/24/20 9:32 AM, Samudrala, Sridhar wrote:
> Adding Dave, Eric for review and see if we can get this in via net-next
> as this is mainly useful for networking workloads doing busypoll.
>
> Thanks
> Sridhar
>
> On 6/19/2020 11:13 AM, Sridhar Samudrala wrote:
>> This patch triggers non-blocking busy poll when busy_poll is enabled and
>> epoll is called with a timeout of 0 and is associated with a napi_id.
>> This enables an app thread to go through napi poll routine once by calling
>> epoll with a 0 timeout.
>>
>> poll/select with a 0 timeout behave in a similar manner.
>>
>> Signed-off-by: Sridhar Samudrala <sridhar.samudrala@xxxxxxxxx>
>> ---
>> fs/eventpoll.c | 13 +++++++++++++
>> 1 file changed, 13 insertions(+)
>>
>> diff --git a/fs/eventpoll.c b/fs/eventpoll.c
>> index 12eebcdea9c8..5f55078d6381 100644
>> --- a/fs/eventpoll.c
>> +++ b/fs/eventpoll.c
>> @@ -1847,6 +1847,19 @@ static int ep_poll(struct eventpoll *ep, struct epoll_event __user *events,
>> eavail = ep_events_available(ep);
>> write_unlock_irq(&ep->lock);
>> + /*
>> + * Trigger non-blocking busy poll if timeout is 0 and there are
>> + * no events available. Passing timed_out(1) to ep_busy_loop
>> + * will make sure that busy polling is triggered only once and
>> + * only if sysctl.net.core.busy_poll is set to non-zero value.
>> + */
>> + if (!eavail) {
Maybe avoid all this stuff for the typical case of busy poll being not used ?
if (!evail && net_busy_loop_on)) {
>> + ep_busy_loop(ep, timed_out);
>> + write_lock_irq(&ep->lock);
>> + eavail = ep_events_available(ep);
>> + write_unlock_irq(&ep->lock);
>> + }
>> +
>> goto send_events;
>> }
>>
