On Thu, Feb 08, 2024 at 06:46:25PM +0100, Eric Dumazet wrote:
> On Mon, Feb 5, 2024 at 10:05 PM Joe Damato <jdamato@xxxxxxxxxx> wrote:
> >
> > Allow busy polling on a per-epoll context basis. The per-epoll context
> > usec timeout value is preferred, but the pre-existing system wide sysctl
> > value is still supported if it specified.
> >
> > Signed-off-by: Joe Damato <jdamato@xxxxxxxxxx>
> > ---
> > fs/eventpoll.c | 49 +++++++++++++++++++++++++++++++++++++++++++++----
> > 1 file changed, 45 insertions(+), 4 deletions(-)
> >
> > diff --git a/fs/eventpoll.c b/fs/eventpoll.c
> > index 3534d36a1474..ce75189d46df 100644
> > --- a/fs/eventpoll.c
> > +++ b/fs/eventpoll.c
> > @@ -227,6 +227,8 @@ struct eventpoll {
> > #ifdef CONFIG_NET_RX_BUSY_POLL
> > /* used to track busy poll napi_id */
> > unsigned int napi_id;
> > + /* busy poll timeout */
> > + u64 busy_poll_usecs;
> > #endif
> >
> > #ifdef CONFIG_DEBUG_LOCK_ALLOC
> > @@ -386,12 +388,44 @@ static inline int ep_events_available(struct eventpoll *ep)
> > READ_ONCE(ep->ovflist) != EP_UNACTIVE_PTR;
> > }
> >
> > +/**
> > + * busy_loop_ep_timeout - check if busy poll has timed out. The timeout value
> > + * from the epoll instance ep is preferred, but if it is not set fallback to
> > + * the system-wide global via busy_loop_timeout.
> > + *
> > + * @start_time: The start time used to compute the remaining time until timeout.
> > + * @ep: Pointer to the eventpoll context.
> > + *
> > + * Return: true if the timeout has expired, false otherwise.
> > + */
> > +static inline bool busy_loop_ep_timeout(unsigned long start_time, struct eventpoll *ep)
> > +{
> > +#ifdef CONFIG_NET_RX_BUSY_POLL
>
> It seems this local helper is only called from code compiled when
> CONFIG_NET_RX_BUSY_POLL
> is set.
>
> Not sure why you need an #ifdef here.
Thanks, you are right.
I'll move this down to be within CONFIG_NET_RX_BUSY_POLL and get rid of the
#ifdef for the v7.
Thanks for your review.
> > + unsigned long bp_usec = READ_ONCE(ep->busy_poll_usecs);
> > +
> > + if (bp_usec) {
> > + unsigned long end_time = start_time + bp_usec;
> > + unsigned long now = busy_loop_current_time();
> > +
> > + return time_after(now, end_time);
> > + } else {
> > + return busy_loop_timeout(start_time);
> > + }
> > +#endif
> > + return true;
> > +}
> > +
> > #ifdef CONFIG_NET_RX_BUSY_POLL
> > +static bool ep_busy_loop_on(struct eventpoll *ep)
> > +{
> > + return !!ep->busy_poll_usecs || net_busy_loop_on();
> > +}
> > +
> > static bool ep_busy_loop_end(void *p, unsigned long start_time)
> > {
> > struct eventpoll *ep = p;
> >
> > - return ep_events_available(ep) || busy_loop_timeout(start_time);
> > + return ep_events_available(ep) || busy_loop_ep_timeout(start_time, ep);
> > }
> >
> > /*
> > @@ -404,7 +438,7 @@ static bool ep_busy_loop(struct eventpoll *ep, int nonblock)
> > {
> > unsigned int napi_id = READ_ONCE(ep->napi_id);
> >
> > - if ((napi_id >= MIN_NAPI_ID) && net_busy_loop_on()) {
> > + if ((napi_id >= MIN_NAPI_ID) && ep_busy_loop_on(ep)) {
> > napi_busy_loop(napi_id, nonblock ? NULL : ep_busy_loop_end, ep, false,
> > BUSY_POLL_BUDGET);
> > if (ep_events_available(ep))
> > @@ -430,7 +464,8 @@ static inline void ep_set_busy_poll_napi_id(struct epitem *epi)
> > struct socket *sock;
> > struct sock *sk;
> >
> > - if (!net_busy_loop_on())
> > + ep = epi->ep;
> > + if (!ep_busy_loop_on(ep))
> > return;
> >
> > sock = sock_from_file(epi->ffd.file);
> > @@ -442,7 +477,6 @@ static inline void ep_set_busy_poll_napi_id(struct epitem *epi)
> > return;
> >
> > napi_id = READ_ONCE(sk->sk_napi_id);
> > - ep = epi->ep;
> >
> > /* Non-NAPI IDs can be rejected
> > * or
> > @@ -466,6 +500,10 @@ static inline void ep_set_busy_poll_napi_id(struct epitem *epi)
> > {
> > }
> >
> > +static inline bool ep_busy_loop_on(struct eventpoll *ep)
> > +{
> > + return false;
> > +}
> > #endif /* CONFIG_NET_RX_BUSY_POLL */
> >
> > /*
> > @@ -2058,6 +2096,9 @@ static int do_epoll_create(int flags)
> > error = PTR_ERR(file);
> > goto out_free_fd;
> > }
> > +#ifdef CONFIG_NET_RX_BUSY_POLL
> > + ep->busy_poll_usecs = 0;
> > +#endif
> > ep->file = file;
> > fd_install(fd, file);
> > return fd;
> > --
> > 2.25.1
> >
