| Message ID | 20240131180811.23566-2-jdamato@fastly.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | Per epoll context busy poll support | expand |
On Wed, Jan 31, 2024 at 06:08:03PM +0000, Joe Damato 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. > > Note that this change uses an xor: either per epoll instance busy polling > is enabled on the epoll instance or system wide epoll is enabled. Enabling > both is disallowed. I just realized that I updated the code below to use a an or (||) instead of xor (^), but forgot to update the commit message. I can fix this and send a v6. > > Signed-off-by: Joe Damato <jdamato@fastly.com> > --- > 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 > + 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 >
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 + 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;
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. Note that this change uses an xor: either per epoll instance busy polling is enabled on the epoll instance or system wide epoll is enabled. Enabling both is disallowed. Signed-off-by: Joe Damato <jdamato@fastly.com> --- fs/eventpoll.c | 49 +++++++++++++++++++++++++++++++++++++++++++++---- 1 file changed, 45 insertions(+), 4 deletions(-)