From: Andrew Morton <akpm@linux-foundation.org>
To: akpm@linux-foundation.org, edumazet@google.com,
guantaol@google.com, khazhy@google.com, linux-mm@kvack.org,
mm-commits@vger.kernel.org, soheil@google.com,
torvalds@linux-foundation.org, willemb@google.com
Subject: [patch 10/78] epoll: simplify and optimize busy loop logic
Date: Fri, 18 Dec 2020 14:01:57 -0800 [thread overview]
Message-ID: <20201218220157.x9tlaAvwR%akpm@linux-foundation.org> (raw)
In-Reply-To: <20201218140046.497484741326828e5b5d46ec@linux-foundation.org>
From: Soheil Hassas Yeganeh <soheil@google.com>
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@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>
---
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;
_
next prev parent reply other threads:[~2020-12-18 22:03 UTC|newest]
Thread overview: 89+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-12-18 22:00 incoming Andrew Morton
2020-12-18 22:01 ` [patch 01/78] mm/memcg: bail early from swap accounting if memcg disabled Andrew Morton
2020-12-18 22:01 ` [patch 02/78] mm/memcg: warning on !memcg after readahead page charged Andrew Morton
2020-12-18 22:01 ` [patch 03/78] mm/memcg: remove unused definitions Andrew Morton
2020-12-18 22:01 ` [patch 04/78] mm, kvm: account kvm_vcpu_mmap to kmemcg Andrew Morton
2020-12-18 22:01 ` [patch 05/78] mm/memcontrol:rewrite mem_cgroup_page_lruvec() Andrew Morton
2020-12-18 22:01 ` [patch 06/78] epoll: check for events when removing a timed out thread from the wait queue Andrew Morton
2020-12-18 22:01 ` [patch 07/78] epoll: simplify signal handling Andrew Morton
2020-12-18 22:01 ` [patch 08/78] epoll: pull fatal signal checks into ep_send_events() Andrew Morton
2020-12-18 22:01 ` [patch 09/78] epoll: move eavail next to the list_empty_careful check Andrew Morton
2020-12-18 22:01 ` Andrew Morton [this message]
2020-12-18 22:02 ` [patch 11/78] epoll: pull all code between fetch_events and send_event into the loop Andrew Morton
2020-12-18 22:02 ` [patch 12/78] epoll: replace gotos with a proper loop Andrew Morton
2020-12-18 22:02 ` [patch 13/78] epoll: eliminate unnecessary lock for zero timeout Andrew Morton
2020-12-18 22:02 ` [patch 14/78] kasan: drop unnecessary GPL text from comment headers Andrew Morton
2020-12-18 22:02 ` [patch 15/78] kasan: KASAN_VMALLOC depends on KASAN_GENERIC Andrew Morton
2020-12-18 22:02 ` [patch 16/78] kasan: group vmalloc code Andrew Morton
2020-12-18 22:02 ` [patch 17/78] kasan: shadow declarations only for software modes Andrew Morton
2020-12-18 22:02 ` [patch 18/78] kasan: rename (un)poison_shadow to (un)poison_range Andrew Morton
2020-12-18 22:02 ` [patch 19/78] kasan: rename KASAN_SHADOW_* to KASAN_GRANULE_* Andrew Morton
2020-12-18 22:02 ` [patch 20/78] kasan: only build init.c for software modes Andrew Morton
2020-12-18 22:02 ` [patch 21/78] kasan: split out shadow.c from common.c Andrew Morton
2020-12-19 0:28 ` Marco Elver
2020-12-19 1:13 ` Andrew Morton
2020-12-19 10:01 ` Marco Elver
2020-12-19 10:11 ` Marco Elver
2020-12-19 18:01 ` Andrey Konovalov
2020-12-19 19:17 ` Linus Torvalds
2020-12-19 19:26 ` Linus Torvalds
2020-12-21 9:46 ` Alexander Potapenko
2020-12-21 17:41 ` Linus Torvalds
2020-12-22 18:38 ` Andrew Morton
2020-12-18 22:02 ` [patch 22/78] kasan: define KASAN_MEMORY_PER_SHADOW_PAGE Andrew Morton
2020-12-18 22:02 ` [patch 23/78] kasan: rename report and tags files Andrew Morton
2020-12-18 22:02 ` [patch 24/78] kasan: don't duplicate config dependencies Andrew Morton
2020-12-18 22:02 ` [patch 25/78] kasan: hide invalid free check implementation Andrew Morton
2020-12-18 22:02 ` [patch 26/78] kasan: decode stack frame only with KASAN_STACK_ENABLE Andrew Morton
2020-12-18 22:02 ` [patch 27/78] kasan, arm64: only init shadow for software modes Andrew Morton
2020-12-18 22:02 ` [patch 28/78] kasan, arm64: only use kasan_depth " Andrew Morton
2020-12-18 22:03 ` [patch 29/78] kasan, arm64: move initialization message Andrew Morton
2020-12-18 22:03 ` [patch 30/78] kasan, arm64: rename kasan_init_tags and mark as __init Andrew Morton
2020-12-18 22:03 ` [patch 31/78] kasan: rename addr_has_shadow to addr_has_metadata Andrew Morton
2020-12-18 22:03 ` [patch 32/78] kasan: rename print_shadow_for_address to print_memory_metadata Andrew Morton
2020-12-18 22:03 ` [patch 33/78] kasan: rename SHADOW layout macros to META Andrew Morton
2020-12-18 22:03 ` [patch 34/78] kasan: separate metadata_fetch_row for each mode Andrew Morton
2020-12-18 22:03 ` [patch 35/78] kasan: introduce CONFIG_KASAN_HW_TAGS Andrew Morton
2020-12-18 22:03 ` [patch 36/78] arm64: enable armv8.5-a asm-arch option Andrew Morton
2020-12-18 22:03 ` [patch 37/78] arm64: mte: add in-kernel MTE helpers Andrew Morton
2020-12-18 22:03 ` [patch 38/78] arm64: mte: reset the page tag in page->flags Andrew Morton
2020-12-18 22:03 ` [patch 39/78] arm64: mte: add in-kernel tag fault handler Andrew Morton
2020-12-18 22:03 ` [patch 40/78] arm64: kasan: allow enabling in-kernel MTE Andrew Morton
2020-12-18 22:03 ` [patch 41/78] arm64: mte: convert gcr_user into an exclude mask Andrew Morton
2020-12-18 22:03 ` [patch 42/78] arm64: mte: switch GCR_EL1 in kernel entry and exit Andrew Morton
2020-12-18 22:03 ` [patch 43/78] kasan, mm: untag page address in free_reserved_area Andrew Morton
2020-12-18 22:03 ` [patch 44/78] arm64: kasan: align allocations for HW_TAGS Andrew Morton
2020-12-18 22:03 ` [patch 45/78] arm64: kasan: add arch layer for memory tagging helpers Andrew Morton
2020-12-18 22:03 ` [patch 46/78] kasan: define KASAN_GRANULE_SIZE for HW_TAGS Andrew Morton
2020-12-18 22:03 ` [patch 47/78] kasan, x86, s390: update undef CONFIG_KASAN Andrew Morton
2020-12-18 22:04 ` [patch 48/78] kasan, arm64: expand CONFIG_KASAN checks Andrew Morton
2020-12-18 22:04 ` [patch 49/78] kasan, arm64: implement HW_TAGS runtime Andrew Morton
2020-12-18 22:04 ` [patch 50/78] kasan, arm64: print report from tag fault handler Andrew Morton
2020-12-18 22:04 ` [patch 51/78] kasan, mm: reset tags when accessing metadata Andrew Morton
2020-12-18 22:04 ` [patch 52/78] kasan, arm64: enable CONFIG_KASAN_HW_TAGS Andrew Morton
2020-12-18 22:04 ` [patch 53/78] kasan: add documentation for hardware tag-based mode Andrew Morton
2020-12-18 22:04 ` [patch 54/78] kselftest/arm64: check GCR_EL1 after context switch Andrew Morton
2020-12-18 22:04 ` [patch 55/78] kasan: simplify quarantine_put call site Andrew Morton
2020-12-18 22:04 ` [patch 56/78] kasan: rename get_alloc/free_info Andrew Morton
2020-12-18 22:04 ` [patch 57/78] kasan: introduce set_alloc_info Andrew Morton
2020-12-18 22:04 ` [patch 58/78] kasan, arm64: unpoison stack only with CONFIG_KASAN_STACK Andrew Morton
2020-12-18 22:04 ` [patch 59/78] kasan: allow VMAP_STACK for HW_TAGS mode Andrew Morton
2020-12-18 22:04 ` [patch 60/78] kasan: remove __kasan_unpoison_stack Andrew Morton
2020-12-18 22:04 ` [patch 61/78] kasan: inline kasan_reset_tag for tag-based modes Andrew Morton
2020-12-18 22:04 ` [patch 62/78] kasan: inline random_tag for HW_TAGS Andrew Morton
2020-12-18 22:04 ` [patch 63/78] kasan: open-code kasan_unpoison_slab Andrew Morton
2020-12-18 22:04 ` [patch 64/78] kasan: inline (un)poison_range and check_invalid_free Andrew Morton
2020-12-18 22:05 ` [patch 65/78] kasan: add and integrate kasan boot parameters Andrew Morton
2020-12-18 22:05 ` [patch 66/78] kasan, mm: check kasan_enabled in annotations Andrew Morton
2020-12-18 22:05 ` [patch 67/78] kasan, mm: rename kasan_poison_kfree Andrew Morton
2020-12-18 22:05 ` [patch 68/78] kasan: don't round_up too much Andrew Morton
2020-12-18 22:05 ` [patch 69/78] kasan: simplify assign_tag and set_tag calls Andrew Morton
2020-12-18 22:05 ` [patch 70/78] kasan: clarify comment in __kasan_kfree_large Andrew Morton
2020-12-18 22:05 ` [patch 71/78] kasan: sanitize objects when metadata doesn't fit Andrew Morton
2020-12-18 22:05 ` [patch 72/78] kasan, mm: allow cache merging with no metadata Andrew Morton
2020-12-18 22:05 ` [patch 73/78] kasan: update documentation Andrew Morton
2020-12-18 22:05 ` [patch 74/78] mm/Kconfig: fix spelling mistake "whats" -> "what's" Andrew Morton
2020-12-18 22:05 ` [patch 75/78] epoll: convert internal api to timespec64 Andrew Morton
2020-12-18 22:05 ` [patch 76/78] epoll: add syscall epoll_pwait2 Andrew Morton
2020-12-18 22:05 ` [patch 77/78] epoll: wire up " Andrew Morton
2020-12-18 22:05 ` [patch 78/78] selftests/filesystems: expand epoll with epoll_pwait2 Andrew Morton
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