From 39732ca5af4b09f4db561149041ddad7211019a5 Mon Sep 17 00:00:00 2001 From: Eric Wong Date: Tue, 30 Apr 2013 15:27:38 -0700 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. [akpm@linux-foundation.org: use __packed, for all architectures] Signed-off-by: Eric Wong Cc: Davide Libenzi Cc: Al Viro Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- Reading git-format-patch failed