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authorNicholas Piggin <npiggin@gmail.com>2021-09-07 20:00:00 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2021-09-08 11:50:27 -0700
commit1e1c15839df084f4011825fee922aa976c9159dc (patch)
treeeba0d3e4771362a9032bb3637607cd41f52b2ae6 /include/linux/sched
parent4ce9f970457899defdf68e26e0502c7245002eb3 (diff)
fs/epoll: use a per-cpu counter for user's watches count
This counter tracks the number of watches a user has, to compare against the 'max_user_watches' limit. This causes a scalability bottleneck on SPECjbb2015 on large systems as there is only one user. Changing to a per-cpu counter increases throughput of the benchmark by about 30% on a 16-socket, > 1000 thread system. [rdunlap@infradead.org: fix build errors in kernel/user.c when CONFIG_EPOLL=n] [npiggin@gmail.com: move ifdefs into wrapper functions, slightly improve panic message] Link: https://lkml.kernel.org/r/1628051945.fens3r99ox.astroid@bobo.none [akpm@linux-foundation.org: tweak user_epoll_alloc(), per Guenter] Link: https://lkml.kernel.org/r/20210804191421.GA1900577@roeck-us.net Link: https://lkml.kernel.org/r/20210802032013.2751916-1-npiggin@gmail.com Signed-off-by: Nicholas Piggin <npiggin@gmail.com> Reported-by: Anton Blanchard <anton@ozlabs.org> Cc: Alexander Viro <viro@zeniv.linux.org.uk> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'include/linux/sched')
-rw-r--r--include/linux/sched/user.h3
1 files changed, 2 insertions, 1 deletions
diff --git a/include/linux/sched/user.h b/include/linux/sched/user.h
index 2462f7d07695..00ed419dd464 100644
--- a/include/linux/sched/user.h
+++ b/include/linux/sched/user.h
@@ -4,6 +4,7 @@
#include <linux/uidgid.h>
#include <linux/atomic.h>
+#include <linux/percpu_counter.h>
#include <linux/refcount.h>
#include <linux/ratelimit.h>
@@ -13,7 +14,7 @@
struct user_struct {
refcount_t __count; /* reference count */
#ifdef CONFIG_EPOLL
- atomic_long_t epoll_watches; /* The number of file descriptors currently watched */
+ struct percpu_counter epoll_watches; /* The number of file descriptors currently watched */
#endif
unsigned long unix_inflight; /* How many files in flight in unix sockets */
atomic_long_t pipe_bufs; /* how many pages are allocated in pipe buffers */