cgroups: make swap accounting default behavior configurable

Swap accounting can be configured by CONFIG_CGROUP_MEM_RES_CTLR_SWAP
configuration option and then it is turned on by default.  There is a boot
option (noswapaccount) which can disable this feature.

This makes it hard for distributors to enable the configuration option as
this feature leads to a bigger memory consumption and this is a no-go for
general purpose distribution kernel.  On the other hand swap accounting
may be very usuful for some workloads.

This patch adds a new configuration option which controls the default
behavior (CGROUP_MEM_RES_CTLR_SWAP_ENABLED).  If the option is selected
then the feature is turned on by default.

It also adds a new boot parameter swapaccount[=1|0] which enhances the
original noswapaccount parameter semantic by means of enable/disable logic
(defaults to 1 if no value is provided to be still consistent with
noswapaccount).

The default behavior is unchanged (if CONFIG_CGROUP_MEM_RES_CTLR_SWAP is
enabled then CONFIG_CGROUP_MEM_RES_CTLR_SWAP_ENABLED is enabled as well)

Signed-off-by: Michal Hocko <mhocko@suse.cz>
Acked-by: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
Cc: Balbir Singh <balbir@linux.vnet.ibm.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 5 insertions, 0 deletions

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 92e83e53148..cdd2a6e8a3b 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -2385,6 +2385,11 @@ and is between 256 and 4096 characters. It is defined in the file
                         improve throughput, but will also increase the
                         amount of memory reserved for use by the client.
 
+        swapaccount[=0|1]
+                        [KNL] Enable accounting of swap in memory resource
+                        controller if no parameter or 1 is given or disable
+                        it if 0 is given (See Documentation/cgroups/memory.txt)
+
         swiotlb=        [IA-64] Number of I/O TLB slabs
 
         switches=       [HW,M68k]