On Fri 11-03-16 13:12:47, Vladimir Davydov wrote:
> These fields are used for dumping info about allocation that triggered
> OOM. For cgroup this information doesn't make much sense, because OOM
> killer is always invoked from page fault handler.
The oom killer is indeed invoked in a different context but why printing
the original mask and order doesn't make any sense? Doesn't it help to
see that the reclaim has failed because of GFP_NOFS?
> It isn't worth the
> space these fields occupy in the task_struct.
struct mem_cgroup * memcg_in_oom; /* 8456 8 */
gfp_t memcg_oom_gfp_mask; /* 8464 4 */
int memcg_oom_order; /* 8468 4 */
unsigned int memcg_nr_pages_over_high; /* 8472 4 */
/* XXX 4 bytes hole, try to pack */
struct uprobe_task * utask; /* 8480 8 */
int pagefault_disabled; /* 8488 4 */
/* XXX 20 bytes hole, try to pack */
/* --- cacheline 133 boundary (8512 bytes) --- */
struct thread_struct thread; /* 8512 4352 */
/* --- cacheline 201 boundary (12864 bytes) --- */
/* size: 12864, cachelines: 201, members: 185 */
vs.
struct mem_cgroup * memcg_in_oom; /* 8456 8 */
unsigned int memcg_nr_pages_over_high; /* 8464 4 */
/* XXX 4 bytes hole, try to pack */
struct uprobe_task * utask; /* 8472 8 */
int pagefault_disabled; /* 8480 4 */
/* XXX 4 bytes hole, try to pack */
struct task_struct * oom_reaper_list; /* 8488 8 */
/* XXX 16 bytes hole, try to pack */
/* --- cacheline 133 boundary (8512 bytes) --- */
struct thread_struct thread; /* 8512 4352 */
/* --- cacheline 201 boundary (12864 bytes) --- */
/* size: 12864, cachelines: 201, members: 184 */
So it doesn't even seem to save any space in the config I am using. Does
it shrink the size of the structure for you?
>
> Signed-off-by: Vladimir Davydov <vdavydov@xxxxxxxxxxxxx>
> ---
> include/linux/sched.h | 2 --
> mm/memcontrol.c | 14 +++++---------
> 2 files changed, 5 insertions(+), 11 deletions(-)
>
> diff --git a/include/linux/sched.h b/include/linux/sched.h
> index ba8d8355c93a..626f5da5c43e 100644
> --- a/include/linux/sched.h
> +++ b/include/linux/sched.h
> @@ -1839,8 +1839,6 @@ struct task_struct {
> #endif
> #ifdef CONFIG_MEMCG
> struct mem_cgroup *memcg_in_oom;
> - gfp_t memcg_oom_gfp_mask;
> - int memcg_oom_order;
>
> /* number of pages to reclaim on returning to userland */
> unsigned int memcg_nr_pages_over_high;
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index 36db05fa8acb..a217b1374c32 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -1232,14 +1232,13 @@ static unsigned long mem_cgroup_get_limit(struct mem_cgroup *memcg)
> return limit;
> }
>
> -static bool mem_cgroup_out_of_memory(struct mem_cgroup *memcg, gfp_t gfp_mask,
> - int order)
> +static bool mem_cgroup_out_of_memory(struct mem_cgroup *memcg)
> {
> struct oom_control oc = {
> .zonelist = NULL,
> .nodemask = NULL,
> - .gfp_mask = gfp_mask,
> - .order = order,
> + .gfp_mask = GFP_KERNEL,
> + .order = 0,
> };
> struct mem_cgroup *iter;
> unsigned long chosen_points = 0;
> @@ -1605,8 +1604,6 @@ static void mem_cgroup_oom(struct mem_cgroup *memcg, gfp_t mask, int order)
> */
> css_get(&memcg->css);
> current->memcg_in_oom = memcg;
> - current->memcg_oom_gfp_mask = mask;
> - current->memcg_oom_order = order;
> }
>
> /**
> @@ -1656,8 +1653,7 @@ bool mem_cgroup_oom_synchronize(bool handle)
> if (locked && !memcg->oom_kill_disable) {
> mem_cgroup_unmark_under_oom(memcg);
> finish_wait(&memcg_oom_waitq, &owait.wait);
> - mem_cgroup_out_of_memory(memcg, current->memcg_oom_gfp_mask,
> - current->memcg_oom_order);
> + mem_cgroup_out_of_memory(memcg);
> } else {
> schedule();
> mem_cgroup_unmark_under_oom(memcg);
> @@ -5063,7 +5059,7 @@ static ssize_t memory_max_write(struct kernfs_open_file *of,
> }
>
> mem_cgroup_events(memcg, MEMCG_OOM, 1);
> - if (!mem_cgroup_out_of_memory(memcg, GFP_KERNEL, 0))
> + if (!mem_cgroup_out_of_memory(memcg))
> break;
> }
>
> --
> 2.1.4
--
Michal Hocko
SUSE Labs
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