On Wed 14-11-12 01:15:22, David Rientjes wrote:
> To lock the entire system from parallel oom killing, it's possible to
> pass in a zonelist with all zones rather than using
> for_each_populated_zone() for the iteration. This obsoletes
> try_set_system_oom() and clear_system_oom() so that they can be removed.
>
> Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
> Cc: KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxxxxxxx>
> Cc: Michal Hocko <mhocko@xxxxxxx>
> Signed-off-by: David Rientjes <rientjes@xxxxxxxxxx>
The only _potential_ problem I can see with this is that if we ever have
a HW which requires that a node zonelist doesn't contain others nodes'
zones then this wouldn't work. I do not think such a HW exists. Such a HW
would need more changes in the code anyway.
so
Reviewed-by: Michal Hocko <mhocko@xxxxxxx>
> ---
> mm/oom_kill.c | 49 +++++++------------------------------------------
> 1 files changed, 7 insertions(+), 42 deletions(-)
>
> diff --git a/mm/oom_kill.c b/mm/oom_kill.c
> --- a/mm/oom_kill.c
> +++ b/mm/oom_kill.c
> @@ -591,43 +591,6 @@ void clear_zonelist_oom(struct zonelist *zonelist, gfp_t gfp_mask)
> spin_unlock(&zone_scan_lock);
> }
>
> -/*
> - * Try to acquire the oom killer lock for all system zones. Returns zero if a
> - * parallel oom killing is taking place, otherwise locks all zones and returns
> - * non-zero.
> - */
> -static int try_set_system_oom(void)
> -{
> - struct zone *zone;
> - int ret = 1;
> -
> - spin_lock(&zone_scan_lock);
> - for_each_populated_zone(zone)
> - if (zone_is_oom_locked(zone)) {
> - ret = 0;
> - goto out;
> - }
> - for_each_populated_zone(zone)
> - zone_set_flag(zone, ZONE_OOM_LOCKED);
> -out:
> - spin_unlock(&zone_scan_lock);
> - return ret;
> -}
> -
> -/*
> - * Clears ZONE_OOM_LOCKED for all system zones so that failed allocation
> - * attempts or page faults may now recall the oom killer, if necessary.
> - */
> -static void clear_system_oom(void)
> -{
> - struct zone *zone;
> -
> - spin_lock(&zone_scan_lock);
> - for_each_populated_zone(zone)
> - zone_clear_flag(zone, ZONE_OOM_LOCKED);
> - spin_unlock(&zone_scan_lock);
> -}
> -
> /**
> * out_of_memory - kill the "best" process when we run out of memory
> * @zonelist: zonelist pointer
> @@ -708,15 +671,17 @@ out:
>
> /*
> * The pagefault handler calls here because it is out of memory, so kill a
> - * memory-hogging task. If a populated zone has ZONE_OOM_LOCKED set, a parallel
> - * oom killing is already in progress so do nothing. If a task is found with
> - * TIF_MEMDIE set, it has been killed so do nothing and allow it to exit.
> + * memory-hogging task. If any populated zone has ZONE_OOM_LOCKED set, a
> + * parallel oom killing is already in progress so do nothing.
> */
> void pagefault_out_of_memory(void)
> {
> - if (try_set_system_oom()) {
> + struct zonelist *zonelist = node_zonelist(first_online_node,
> + GFP_KERNEL);
> +
> + if (try_set_zonelist_oom(zonelist, GFP_KERNEL)) {
> out_of_memory(NULL, 0, 0, NULL, false);
> - clear_system_oom();
> + clear_zonelist_oom(zonelist, GFP_KERNEL);
> }
> schedule_timeout_killable(1);
> }
--
Michal Hocko
SUSE Labs
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