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cgroup memory controller: document huge memory/cache overhead in Kconfig

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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 <ak@suse.de>
Cc: Balbir Singh <balbir@in.ibm.com>
Acked-by: Paul Menage <menage@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Andi Kleen 2008-02-23 15:24:02 -08:00 committed by Linus Torvalds
parent 00d6296145
commit 0835ab53ea
1 changed files with 8 additions and 0 deletions
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init/Kconfig
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@ -394,6 +394,14 @@ config CGROUP_MEM_CONT
Provides a memory controller that manages both page cache and
RSS memory.
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.
config PROC_PID_CPUSET
bool "Include legacy /proc/<pid>/cpuset file"
depends on CPUSETS