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| author |   Soheil Hassas Yeganeh <soheil@google.com> | 2020-12-18 14:01:57 -0800 |
|---|---|---|
| committer |   Linus Torvalds <torvalds@linux-foundation.org> | 2020-12-19 11:18:37 -0800 |
| commit | 1493c47fb140ddd9e5c291f0c0da3fb03741c766 (patch) | |
| tree | 1317d23bb8bc4c9db641ec0e841dbe7c2f294743 /fs/eventpoll.c | |
| parent | epoll: move eavail next to the list_empty_careful check (diff) | |
| download | linux-dev-1493c47fb140ddd9e5c291f0c0da3fb03741c766.tar.xz linux-dev-1493c47fb140ddd9e5c291f0c0da3fb03741c766.zip | |
epoll: simplify and optimize busy loop logic
ep_events_available() is called multiple times around the busy loop logic,
even though the logic is generally not used. ep_reset_busy_poll_napi_id()
is similarly always called, even when busy loop is not used.
Eliminate ep_reset_busy_poll_napi_id() and inline it inside
ep_busy_loop(). Make ep_busy_loop() return whether there are any events
available after the busy loop. This will eliminate unnecessary loads and
branches, and simplifies the loop.
Link: https://lkml.kernel.org/r/20201106231635.3528496-6-soheil.kdev@gmail.com
Signed-off-by: Soheil Hassas Yeganeh <soheil@google.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Willem de Bruijn <willemb@google.com>
Reviewed-by: Khazhismel Kumykov <khazhy@google.com>
Cc: Guantao Liu <guantaol@google.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'fs/eventpoll.c')
| -rw-r--r-- | fs/eventpoll.c | 40 |
1 files changed, 17 insertions, 23 deletions
diff --git a/fs/eventpoll.c b/fs/eventpoll.c index d8eef2157587..03d0ac076a16 100644 --- a/fs/eventpoll.c +++ b/fs/eventpoll.c @@ -389,19 +389,24 @@ static bool ep_busy_loop_end(void *p, unsigned long start_time) * * we must do our busy polling with irqs enabled */ -static void ep_busy_loop(struct eventpoll *ep, int nonblock) +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) && net_busy_loop_on()) { napi_busy_loop(napi_id, nonblock ? NULL : ep_busy_loop_end, ep, false, BUSY_POLL_BUDGET); -} - -static inline void ep_reset_busy_poll_napi_id(struct eventpoll *ep) -{ - if (ep->napi_id) + if (ep_events_available(ep)) + return true; + /* + * Busy poll timed out. Drop NAPI ID for now, we can add + * it back in when we have moved a socket with a valid NAPI + * ID onto the ready list. + */ ep->napi_id = 0; + return false; + } + return false; } /* @@ -441,12 +446,9 @@ static inline void ep_set_busy_poll_napi_id(struct epitem *epi) #else -static inline void ep_busy_loop(struct eventpoll *ep, int nonblock) -{ -} - -static inline void ep_reset_busy_poll_napi_id(struct eventpoll *ep) +static inline bool ep_busy_loop(struct eventpoll *ep, int nonblock) { + return false; } static inline void ep_set_busy_poll_napi_id(struct epitem *epi) @@ -1772,21 +1774,13 @@ static int ep_poll(struct eventpoll *ep, struct epoll_event __user *events, } fetch_events: - - if (!ep_events_available(ep)) - ep_busy_loop(ep, timed_out); - eavail = ep_events_available(ep); + if (!eavail) + eavail = ep_busy_loop(ep, timed_out); + if (eavail) goto send_events; - /* - * Busy poll timed out. Drop NAPI ID for now, we can add - * it back in when we have moved a socket with a valid NAPI - * ID onto the ready list. - */ - ep_reset_busy_poll_napi_id(ep); - do { if (signal_pending(current)) return -EINTR; |