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. Cc: [EMAIL PROTECTED] Signed-off-by: Andi Kleen <[EMAIL PROTECTED]> Index: linux/init/Kconfig =================================================================== --- linux.orig/init/Kconfig +++ linux/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 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/