Re: [RFC][PATCH 9/11] memcg : mem+swap controlelr kconfig

Daisuke Nishimura
2008-10-27T06:39:11Z

On Thu, 23 Oct 2008 18:12:20 +0900, KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> wrote:
> Config and control variable for mem+swap controller.
>
> This patch adds CONFIG_CGROUP_MEM_RES_CTLR_SWAP
> (memory resource controller swap extension.)
>
> For accounting swap, it's obvious that we have to use additional memory
> to remember "who uses swap". This adds more overhead.
> So, it's better to offer "choice" to users. This patch adds 2 choices.
>
> This patch adds 2 parameters to enable swap extenstion or not.
> - CONFIG
> - boot option
>
> This version uses policy of "default is enable if configured."
> please tell me you dislike this. See patches following this in detail...
>
> Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
>
>
> Documentation/kernel-parameters.txt | 3 +++
> include/linux/memcontrol.h | 3 +++
> init/Kconfig | 16 ++++++++++++++++
> mm/memcontrol.c | 17 +++++++++++++++++
> 4 files changed, 39 insertions(+)
>
> Index: mmotm-2.6.27+/init/Kconfig
> ===================================================================
> --- mmotm-2.6.27+.orig/init/Kconfig
> +++ mmotm-2.6.27+/init/Kconfig
> @@ -613,6 +613,22 @@ config KALLSYMS_EXTRA_PASS
> reported. KALLSYMS_EXTRA_PASS is only a temporary workaround while
> you wait for kallsyms to be fixed.
>
> +config CGROUP_MEM_RES_CTLR_SWAP
> + bool "Memory Resource Controller Swap Extension(EXPERIMENTAL)"
> + depends on CGROUP_MEM_RES_CTLR && SWAP && EXPERIMENTAL
> + help
> + Add swap management feature to memory resource controller. When you
> + enable this, you can limit mem+swap usage per cgroup. In other words,
> + when you disable this, memory resource controller have no cares to
> + usage of swap...a process can exhaust the all swap. This extension
> + is useful when you want to avoid exhausion of swap but this itself
> + adds more overheads and consumes memory for remembering information.
> + Especially if you use 32bit system or small memory system,
> + please be careful to enable this. When memory resource controller
> + is disabled by boot option, this will be automatiaclly disabled and
> + there will be no overhead from this. Even when you set this config=y,
> + if boot option "noswapaccount" is set, swap will not be accounted.
> +
>
hmm... "cgroup_disable=memory" doesn't fully disable this feature.

Even if specifying "cgroup_disable=memory", memory for table of swap_cgroup
is allocated at swapon because "do_swap_account" is not turned off.

I think it can be turned off adding some codes at mem_cgroup_create() like:

===
@@ -1881,6 +1881,8 @@ mem_cgroup_create(struct cgroup_subsys *ss, struct cgroup *cont)
int node;

if (unlikely((cont->parent) == NULL)) {
+ if (mem_cgroup_subsys.disabled)
+ do_swap_account = 0;
mem = &init_mem_cgroup;
cpu_memcgroup_callback(&memcgroup_nb,
(unsigned long)CPU_UP_PREPARE,
===

BTW, is there any reason to call cgroup_init_subsys() even when the subsys
is disabled by boot option?

Thanks,
Daisuke Nishimura.

> config HOTPLUG
> bool "Support for hot-pluggable devices" if EMBEDDED
> Index: mmotm-2.6.27+/mm/memcontrol.c
> ===================================================================
> --- mmotm-2.6.27+.orig/mm/memcontrol.c
> +++ mmotm-2.6.27+/mm/memcontrol.c
> @@ -41,6 +41,13 @@
> struct cgroup_subsys mem_cgroup_subsys __read_mostly;
> #define MEM_CGROUP_RECLAIM_RETRIES 5
>
> +#ifdef CONFIG_CGROUP_MEM_RES_CTLR_SWAP
> +int do_swap_account __read_mostly = 1;
> +#else
> +#define do_swap_account (0)
> +#endif
> +
> +
> /*
> * Statistics for memory cgroup.
> */
> @@ -1658,3 +1665,13 @@ struct cgroup_subsys mem_cgroup_subsys =
> .attach = mem_cgroup_move_task,
> .early_init = 0,
> };
> +
> +#ifdef CONFIG_CGROUP_MEM_RES_CTLR_SWAP
> +
> +static int __init disable_swap_account(char *s)
> +{
> + do_swap_account = 0;
> + return 1;
> +}
> +__setup("noswapaccount", disable_swap_account);
> +#endif
> Index: mmotm-2.6.27+/Documentation/kernel-parameters.txt
> ===================================================================
> --- mmotm-2.6.27+.orig/Documentation/kernel-parameters.txt
> +++ mmotm-2.6.27+/Documentation/kernel-parameters.txt
> @@ -1540,6 +1540,9 @@ and is between 256 and 4096 characters.
>
> nosoftlockup [KNL] Disable the soft-lockup detector.
>
> + noswapaccount [KNL] Disable accounting of swap in memory resource
> + controller. (See Documentation/controllers/memory.txt)
> +
> nosync [HW,M68K] Disables sync negotiation for all devices.
>
> notsc [BUGS=X86-32] Disable Time Stamp Counter
> Index: mmotm-2.6.27+/include/linux/memcontrol.h
> ===================================================================
> --- mmotm-2.6.27+.orig/include/linux/memcontrol.h
> +++ mmotm-2.6.27+/include/linux/memcontrol.h
> @@ -80,6 +80,9 @@ extern void mem_cgroup_record_reclaim_pr
> extern long mem_cgroup_calc_reclaim(struct mem_cgroup *mem, struct zone *zone,
> int priority, enum lru_list lru);
>
> +#ifdef CONFIG_CGROUP_MEM_RES_CTLR_SWAP
> +extern int do_swap_account;
> +#endif
>
> #else /* CONFIG_CGROUP_MEM_RES_CTLR */
> struct mem_cgroup;