On Mon 15-03-21 16:58:37, Aaron Tomlin wrote:
> In the situation where direct reclaim is required to make progress for
> compaction but no_progress_loops is already over the limit of
> MAX_RECLAIM_RETRIES consider invoking the oom killer.
What is the problem you are trying to fix?
>
> Signed-off-by: Aaron Tomlin <atomlin@xxxxxxxxxx>
> ---
> mm/page_alloc.c | 22 ++++++++++++++++++----
> 1 file changed, 18 insertions(+), 4 deletions(-)
>
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index 7a2c89b21115..8d748b1b8d1e 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -4181,6 +4181,16 @@ __alloc_pages_direct_compact(gfp_t gfp_mask, unsigned int order,
> return NULL;
> }
>
> +static inline bool
> +should_try_oom(int no_progress_loops,
> + enum compact_result last_compact_result)
> +{
> + if (no_progress_loops > MAX_RECLAIM_RETRIES && last_compact_result
> + == COMPACT_SKIPPED)
> + return true;
> + return false;
> +}
> +
> static inline bool
> should_compact_retry(struct alloc_context *ac, int order, int alloc_flags,
> enum compact_result compact_result,
> @@ -4547,10 +4557,11 @@ should_reclaim_retry(gfp_t gfp_mask, unsigned order,
> * Make sure we converge to OOM if we cannot make any progress
> * several times in the row.
> */
> - if (*no_progress_loops > MAX_RECLAIM_RETRIES) {
> - /* Before OOM, exhaust highatomic_reserve */
> - return unreserve_highatomic_pageblock(ac, true);
> - }
> + if (*no_progress_loops > MAX_RECLAIM_RETRIES)
> + result false;
> + /* Last chance before OOM, try draining highatomic_reserve once */
> + else if (*no_progress_loops == MAX_RECLAIM_RETRIES)
> + return unreserve_highatomic_pageblock(ac, true)
>
> /*
> * Keep reclaiming pages while there is a chance this will lead
> @@ -4822,6 +4833,8 @@ __alloc_pages_slowpath(gfp_t gfp_mask, unsigned int order,
> did_some_progress > 0, &no_progress_loops))
> goto retry;
>
> + if (should_try_oom(no_progress_loops, compact_result))
> + goto oom:
> /*
> * It doesn't make any sense to retry for the compaction if the order-0
> * reclaim is not able to make any progress because the current
> @@ -4839,6 +4852,7 @@ __alloc_pages_slowpath(gfp_t gfp_mask, unsigned int order,
> if (check_retry_cpuset(cpuset_mems_cookie, ac))
> goto retry_cpuset;
>
> +oom:
> /* Reclaim has failed us, start killing things */
> page = __alloc_pages_may_oom(gfp_mask, order, ac, &did_some_progress);
> if (page)
> --
> 2.26.2
>
--
Michal Hocko
SUSE Labs
