From 5c37b1c68fdd24a894608e64dbe04e86c451b3b9 Mon Sep 17 00:00:00 2001 From: Eric Wong Date: Wed, 20 Mar 2013 15:07:46 +1100 Subject: [PATCH] epoll: trim epitem by one cache line It is common for epoll users to have thousands of epitems, so saving a cache line on every allocation leads to large memory savings. Since epitem allocations are cache-aligned, reducing sizeof(struct epitem) from 136 bytes to 128 bytes will allow it to squeeze under a cache line boundary on x86_64. Via /sys/kernel/slab/eventpoll_epi, I see the following changes on my x86_64 Core2 Duo (which has 64-byte cache alignment): object_size : 192 => 128 objs_per_slab: 21 => 32 Also, add a BUILD_BUG_ON() to check for future accidental breakage. Signed-off-by: Eric Wong Cc: Davide Libenzi Cc: Al Viro Signed-off-by: Andrew Morton --- fs/eventpoll.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/fs/eventpoll.c b/fs/eventpoll.c index 495d15558f42..0edf94dd578e 100644 --- a/fs/eventpoll.c +++ b/fs/eventpoll.c @@ -105,7 +105,7 @@ struct epoll_filefd { struct file *file; int fd; -}; +} EPOLL_PACKED; /* * Structure used to track possible nested calls, for too deep recursions -- 2.39.5