The patch titled
cgroup memory controller: document huge memory/cache overhead in Kconfig
has been added to the -mm tree. Its filename is
cgroup-memory-controller-document-huge-memory-cache-overhead-in-kconfig.patch
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------------------------------------------------------
Subject: cgroup memory controller: document huge memory/cache overhead in
Kconfig
From: Andi Kleen <[EMAIL PROTECTED]>
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 <[EMAIL PROTECTED]>
Cc: Balbir Singh <[EMAIL PROTECTED]>
Acked-by: Paul Menage <[EMAIL PROTECTED]>
Signed-off-by: Andrew Morton <[EMAIL PROTECTED]>
---
init/Kconfig | 8 ++++++++
1 file changed, 8 insertions(+)
diff -puN
init/Kconfig~cgroup-memory-controller-document-huge-memory-cache-overhead-in-kconfig
init/Kconfig
---
a/init/Kconfig~cgroup-memory-controller-document-huge-memory-cache-overhead-in-kconfig
+++ a/init/Kconfig
@@ -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
_
Patches currently in -mm which might be from [EMAIL PROTECTED] are
cgroup-memory-controller-document-huge-memory-cache-overhead-in-kconfig.patch
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