|author||Andi Kleen <firstname.lastname@example.org>||2008-02-23 15:24:02 -0800|
|committer||Linus Torvalds <email@example.com>||2008-02-23 17:12:16 -0800|
cgroup memory controller: document huge memory/cache overhead in Kconfig
Document huge memory/cache overhead of memory controller in Kconfig I was a little surprised that 2.6.25-rc* increased struct page for the memory controller. At least on many x86-64 machines it will not fit into a single cache line now anymore and also costs considerable amounts of RAM. At earlier review I remembered asking for a external data structure for this. It's also quite unobvious that a innocent looking Kconfig option with a single line Kconfig description has such a negative effect. This patch attempts to document these disadvantages at least so that users configuring their kernel can make a informed decision. Signed-off-by: Andi Kleen <firstname.lastname@example.org> Cc: Balbir Singh <email@example.com> Acked-by: Paul Menage <firstname.lastname@example.org> Signed-off-by: Andrew Morton <email@example.com> Signed-off-by: Linus Torvalds <firstname.lastname@example.org>
Diffstat (limited to 'init/Kconfig')
1 files changed, 8 insertions, 0 deletions
diff --git a/init/Kconfig b/init/Kconfig
index dcef8b55011a..f698a5af5007 100644
@@ -394,6 +394,14 @@ config CGROUP_MEM_CONT
Provides a memory controller that manages both page cache and
+ Note that setting this option increases fixed memory overhead
+ associated with each page of memory in the system by 4/8 bytes
+ and also increases cache misses because struct page on many 64bit
+ systems will not fit into a single cache line anymore.
+ Only enable when you're ok with these trade offs and really
+ sure you need the memory controller.
bool "Include legacy /proc/<pid>/cpuset file"
depends on CPUSETS