The patch titled
Subject: epoll: simplify and optimize busy loop logic
has been removed from the -mm tree. Its filename was
epoll-simplify-and-optimize-busy-loop-logic.patch
This patch was dropped because it was merged into mainline or a subsystem tree
------------------------------------------------------
From: Soheil Hassas Yeganeh <soheil@xxxxxxxxxx>
Subject: 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@xxxxxxxxx
Signed-off-by: Soheil Hassas Yeganeh <soheil@xxxxxxxxxx>
Reviewed-by: Eric Dumazet <edumazet@xxxxxxxxxx>
Reviewed-by: Willem de Bruijn <willemb@xxxxxxxxxx>
Reviewed-by: Khazhismel Kumykov <khazhy@xxxxxxxxxx>
Cc: Guantao Liu <guantaol@xxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
fs/eventpoll.c | 40 +++++++++++++++++-----------------------
1 file changed, 17 insertions(+), 23 deletions(-)
--- a/fs/eventpoll.c~epoll-simplify-and-optimize-busy-loop-logic
+++ a/fs/eventpoll.c
@@ -389,19 +389,24 @@ static bool ep_busy_loop_end(void *p, un
*
* 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
#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,
}
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;
_
Patches currently in -mm which might be from soheil@xxxxxxxxxx are
