Re: [PATCH 1/4] Revert "mm, oom: prevent premature OOM killer invocation for high order request"

[Michal Hocko]

On Tue 06-09-16 15:52:55, Vlastimil Babka wrote:
> Commit 6b4e3181d7bd ("mm, oom: prevent premature OOM killer invocation for high
> order request") was intended as a quick fix of OOM regressions for 4.8 and
> stable 4.7.x kernels. For a better long-term solution, we still want to
> consider compaction feedback, which should be possible after some more
> improvements in the following patches.
> 
> This reverts commit 6b4e3181d7bd5ca5ab6f45929e4a5ffa7ab4ab7f.
> 
> Signed-off-by: Vlastimil Babka <vbabka@xxxxxxx>
> Cc: Michal Hocko <mhocko@xxxxxxxxxx>
> Cc: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>
> Cc: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx>
> Cc: David Rientjes <rientjes@xxxxxxxxxx>
> Cc: Rik van Riel <riel@xxxxxxxxxx>

Acked-by: Michal Hocko <mhocko@xxxxxxxx>

> ---
>  mm/page_alloc.c | 51 +++++++++++++++++++++++++++++++++++++++++++++++++--
>  1 file changed, 49 insertions(+), 2 deletions(-)
> 
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index ee3997859f14..1df7694f4ec7 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -3158,6 +3158,54 @@ __alloc_pages_direct_compact(gfp_t gfp_mask, unsigned int order,
>  	return NULL;
>  }
>  
> +static inline bool
> +should_compact_retry(struct alloc_context *ac, int order, int alloc_flags,
> +		     enum compact_result compact_result,
> +		     enum compact_priority *compact_priority,
> +		     int compaction_retries)
> +{
> +	int max_retries = MAX_COMPACT_RETRIES;
> +
> +	if (!order)
> +		return false;
> +
> +	/*
> +	 * compaction considers all the zone as desperately out of memory
> +	 * so it doesn't really make much sense to retry except when the
> +	 * failure could be caused by insufficient priority
> +	 */
> +	if (compaction_failed(compact_result)) {
> +		if (*compact_priority > MIN_COMPACT_PRIORITY) {
> +			(*compact_priority)--;
> +			return true;
> +		}
> +		return false;
> +	}
> +
> +	/*
> +	 * make sure the compaction wasn't deferred or didn't bail out early
> +	 * due to locks contention before we declare that we should give up.
> +	 * But do not retry if the given zonelist is not suitable for
> +	 * compaction.
> +	 */
> +	if (compaction_withdrawn(compact_result))
> +		return compaction_zonelist_suitable(ac, order, alloc_flags);
> +
> +	/*
> +	 * !costly requests are much more important than __GFP_REPEAT
> +	 * costly ones because they are de facto nofail and invoke OOM
> +	 * killer to move on while costly can fail and users are ready
> +	 * to cope with that. 1/4 retries is rather arbitrary but we
> +	 * would need much more detailed feedback from compaction to
> +	 * make a better decision.
> +	 */
> +	if (order > PAGE_ALLOC_COSTLY_ORDER)
> +		max_retries /= 4;
> +	if (compaction_retries <= max_retries)
> +		return true;
> +
> +	return false;
> +}
>  #else
>  static inline struct page *
>  __alloc_pages_direct_compact(gfp_t gfp_mask, unsigned int order,
> @@ -3168,8 +3216,6 @@ __alloc_pages_direct_compact(gfp_t gfp_mask, unsigned int order,
>  	return NULL;
>  }
>  
> -#endif /* CONFIG_COMPACTION */
> -
>  static inline bool
>  should_compact_retry(struct alloc_context *ac, unsigned int order, int alloc_flags,
>  		     enum compact_result compact_result,
> @@ -3196,6 +3242,7 @@ should_compact_retry(struct alloc_context *ac, unsigned int order, int alloc_fla
>  	}
>  	return false;
>  }
> +#endif /* CONFIG_COMPACTION */
>  
>  /* Perform direct synchronous page reclaim */
>  static int
> -- 
> 2.9.3

-- 
Michal Hocko
SUSE Labs