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>

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 92e83e5..cdd2a6e 100644 (file)
--- 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]

diff --git a/init/Kconfig b/init/Kconfig
index 88c1046..c972899 100644 (file)
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -613,6 +613,19 @@ config CGROUP_MEM_RES_CTLR_SWAP
          if boot option "noswapaccount" is set, swap will not be accounted.
          Now, memory usage of swap_cgroup is 2 bytes per entry. If swap page
          size is 4096bytes, 512k per 1Gbytes of swap.
+config CGROUP_MEM_RES_CTLR_SWAP_ENABLED
+       bool "Memory Resource Controller Swap Extension enabled by default"
+       depends on CGROUP_MEM_RES_CTLR_SWAP
+       default y
+       help
+         Memory Resource Controller Swap Extension comes with its price in
+         a bigger memory consumption. General purpose distribution kernels
+         which want to enable the feautre but keep it disabled by default
+         and let the user enable it by swapaccount boot command line
+         parameter should have this option unselected.
+         For those who want to have the feature enabled by default should
+         select this option (if, for some reason, they need to disable it
+         then noswapaccount does the trick).
 
 menuconfig CGROUP_SCHED
        bool "Group CPU scheduler"

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 26218df..7a22b41 100644 (file)
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -61,7 +61,14 @@ struct mem_cgroup *root_mem_cgroup __read_mostly;
 #ifdef CONFIG_CGROUP_MEM_RES_CTLR_SWAP
 /* Turned on only when memory cgroup is enabled && really_do_swap_account = 1 */
 int do_swap_account __read_mostly;
-static int really_do_swap_account __initdata = 1; /* for remember boot option*/
+
+/* for remember boot option*/
+#ifdef CONFIG_CGROUP_MEM_RES_CTLR_SWAP_ENABLED
+static int really_do_swap_account __initdata = 1;
+#else
+static int really_do_swap_account __initdata = 0;
+#endif
+
 #else
 #define do_swap_account                (0)
 #endif
@@ -4920,10 +4927,20 @@ struct cgroup_subsys mem_cgroup_subsys = {
 };
 
 #ifdef CONFIG_CGROUP_MEM_RES_CTLR_SWAP
+static int __init enable_swap_account(char *s)
+{
+       /* consider enabled if no parameter or 1 is given */
+       if (!s || !strcmp(s, "1"))
+               really_do_swap_account = 1;
+       else if (!strcmp(s, "0"))
+               really_do_swap_account = 0;
+       return 1;
+}
+__setup("swapaccount", enable_swap_account);
 
 static int __init disable_swap_account(char *s)
 {
-       really_do_swap_account = 0;
+       enable_swap_account("0");
        return 1;
 }
 __setup("noswapaccount", disable_swap_account);