Hi Andrea,
于 2013/6/5 10:10, Andrea Arcangeli 写道:
> This fixes zone_reclaim_mode by using the min watermark so it won't
> fail in presence of concurrent allocations. This greatly increases the
> reliability of zone_reclaim_mode > 0 also with cache shrinking and THP
> disabled.
>
> This also adds compaction to zone_reclaim so THP enabled won't
> decrease the NUMA locality with /proc/sys/vm/zone_reclaim_mode > 0.
>
> Some checks for __GFP_WAIT and numa_node_id() are moved from the
> zone_reclaim() to the caller so they also apply to the compaction
> logic.
>
> It is important to boot with numa_zonelist_order=n (n means nodes) to
> get more accurate NUMA locality if there are multiple zones per node.
>
> Signed-off-by: Andrea Arcangeli <aarcange@xxxxxxxxxx>
> ---
> mm/internal.h | 1 -
> mm/page_alloc.c | 99 +++++++++++++++++++++++++++++++++++++++++++--------------
> mm/vmscan.c | 17 ----------
> 3 files changed, 75 insertions(+), 42 deletions(-)
>
> diff --git a/mm/internal.h b/mm/internal.h
> index 8562de0..560a1ec 100644
> --- a/mm/internal.h
> +++ b/mm/internal.h
> @@ -339,7 +339,6 @@ static inline void mminit_validate_memmodel_limits(unsigned long *start_pfn,
> }
> #endif /* CONFIG_SPARSEMEM */
>
> -#define ZONE_RECLAIM_NOSCAN -2
> #define ZONE_RECLAIM_FULL -1
> #define ZONE_RECLAIM_SOME 0
> #define ZONE_RECLAIM_SUCCESS 1
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index c13e062..3ca905a 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -1902,7 +1902,9 @@ zonelist_scan:
> BUILD_BUG_ON(ALLOC_NO_WATERMARKS < NR_WMARK);
> if (!(alloc_flags & ALLOC_NO_WATERMARKS)) {
> unsigned long mark;
> - int ret;
> + int ret, node_id, c_ret;
> + bool repeated_compaction, need_compaction;
> + bool contended = false;
>
> mark = zone->watermark[alloc_flags & ALLOC_WMARK_MASK];
> if (zone_watermark_ok(zone, order, mark,
> @@ -1933,35 +1935,84 @@ zonelist_scan:
> !zlc_zone_worth_trying(zonelist, z, allowednodes))
> continue;
>
> - ret = zone_reclaim(zone, gfp_mask, order);
> - switch (ret) {
> - case ZONE_RECLAIM_NOSCAN:
> - /* did not scan */
> + if (!(gfp_mask & __GFP_WAIT) ||
> + (current->flags & PF_MEMALLOC))
> continue;
> - case ZONE_RECLAIM_FULL:
> - /* scanned but unreclaimable */
> +
> + /*
> + * Only reclaim the local zone or on zones
> + * that do not have associated
> + * processors. This will favor the local
> + * processor over remote processors and spread
> + * off node memory allocations as wide as
> + * possible.
> + */
> + node_id = zone_to_nid(zone);
> + if (node_state(node_id, N_CPU) &&
> + node_id != numa_node_id())
> continue;
> - default:
> - /* did we reclaim enough */
> +
> + /*
> + * We're going to do reclaim so allow
> + * allocations up to the MIN watermark, so less
> + * concurrent allocation will fail.
> + */
> + mark = min_wmark_pages(zone);
Target reclaim will be done once under low wmark in vanilla kernel,
however, your patch change it to min wmark, why this behavior change?
> +
> + /* initialize to avoid warnings */
> + c_ret = COMPACT_SKIPPED;
> + ret = ZONE_RECLAIM_FULL;
> +
> + repeated_compaction = false;
> + need_compaction = false;
> + if (!compaction_deferred(preferred_zone, order))
> + need_compaction = order &&
> + (gfp_mask & GFP_KERNEL) == GFP_KERNEL;
> + if (need_compaction) {
> + repeat_compaction:
> + c_ret = compact_zone_order(zone, order,
> + gfp_mask,
> + repeated_compaction,
> + &contended);
> + if (c_ret != COMPACT_SKIPPED &&
> + zone_watermark_ok(zone, order, mark,
> + classzone_idx,
> + alloc_flags)) {
> +#ifdef CONFIG_COMPACTION
> + preferred_zone->compact_considered = 0;
> + preferred_zone->compact_defer_shift = 0;
> +#endif
> + goto try_this_zone;
> + }
> + }
> + /*
> + * reclaim if compaction failed because not
> + * enough memory was available or if
> + * compaction didn't run (order 0) or didn't
> + * succeed.
> + */
> + if (!repeated_compaction || c_ret == COMPACT_SKIPPED) {
> + ret = zone_reclaim(zone, gfp_mask, order);
> if (zone_watermark_ok(zone, order, mark,
> - classzone_idx, alloc_flags))
> + classzone_idx,
> + alloc_flags))
> goto try_this_zone;
> + }
> + if (need_compaction &&
> + (!repeated_compaction ||
> + (c_ret == COMPACT_SKIPPED &&
> + ret == ZONE_RECLAIM_SUCCESS))) {
> + repeated_compaction = true;
> + cond_resched();
> + goto repeat_compaction;
> + }
> + if (need_compaction)
> + defer_compaction(preferred_zone, order);
>
> - /*
> - * Failed to reclaim enough to meet watermark.
> - * Only mark the zone full if checking the min
> - * watermark or if we failed to reclaim just
> - * 1<<order pages or else the page allocator
> - * fastpath will prematurely mark zones full
> - * when the watermark is between the low and
> - * min watermarks.
> - */
> - if (((alloc_flags & ALLOC_WMARK_MASK) == ALLOC_WMARK_MIN) ||
> - ret == ZONE_RECLAIM_SOME)
> - goto this_zone_full;
> -
> + if (!order)
> + goto this_zone_full;
> + else
You do the works should be done in slow path, is it worth?
> continue;
> - }
> }
>
> try_this_zone:
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index 825c631..6a65107 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -3380,7 +3380,6 @@ static int __zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
>
> int zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
> {
> - int node_id;
> int ret;
>
> /*
> @@ -3400,22 +3399,6 @@ int zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
> if (zone->all_unreclaimable)
> return ZONE_RECLAIM_FULL;
>
> - /*
> - * Do not scan if the allocation should not be delayed.
> - */
> - if (!(gfp_mask & __GFP_WAIT) || (current->flags & PF_MEMALLOC))
> - return ZONE_RECLAIM_NOSCAN;
> -
> - /*
> - * Only run zone reclaim on the local zone or on zones that do not
> - * have associated processors. This will favor the local processor
> - * over remote processors and spread off node memory allocations
> - * as wide as possible.
> - */
> - node_id = zone_to_nid(zone);
> - if (node_state(node_id, N_CPU) && node_id != numa_node_id())
> - return ZONE_RECLAIM_NOSCAN;
> -
> ret = __zone_reclaim(zone, gfp_mask, order);
>
> if (!ret)
>
> --
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