Author: Andi Kleen <[EMAIL PROTECTED]>
AuthorDate: Sat Feb 23 15:24:02 2008 -0800
Committer: Linus Torvalds <[EMAIL PROTECTED]>
CommitDate: Sat Feb 23 17:12:16 2008 -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
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]>
Signed-off-by: Linus Torvalds <[EMAIL PROTECTED]>
init/Kconfig | 8 ++++++++
1 files changed, 8 insertions(+), 0 deletions(-)
diff --git a/init/Kconfig b/init/Kconfig
index dcef8b5..f698a5a 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
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