Re: [PATCH 7/9] mm/compaction: factor out code to test if we should run compaction for target order

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On 8/22/2023 9:57 AM, Kemeng Shi wrote:


on 8/19/2023 8:27 PM, Baolin Wang wrote:


On 8/15/2023 8:10 PM, Kemeng Shi wrote:


on 8/15/2023 4:53 PM, Baolin Wang wrote:


On 8/5/2023 7:07 PM, Kemeng Shi wrote:
We always do zone_watermark_ok check and compaction_suitable check
together to test if compaction for target order should be runned.
Factor these code out for preparation to remove repeat code.

Signed-off-by: Kemeng Shi <shikemeng@xxxxxxxxxxxxxxx>
---
    mm/compaction.c | 42 +++++++++++++++++++++++++++++-------------
    1 file changed, 29 insertions(+), 13 deletions(-)

diff --git a/mm/compaction.c b/mm/compaction.c
index b5a699ed526b..26787ebb0297 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -2365,6 +2365,30 @@ bool compaction_zonelist_suitable(struct alloc_context *ac, int order,
        return false;
    }
    +/*
+ * Should we do compaction for target allocation order.
+ * Return COMPACT_SUCCESS if allocation for target order can be already
+ * satisfied
+ * Return COMPACT_SKIPPED if compaction for target order is likely to fail
+ * Return COMPACT_CONTINUE if compaction for target order should be runned
+ */
+static inline enum compact_result
+compaction_suit_allocation_order(struct zone *zone, unsigned int order,
+                 int highest_zoneidx, unsigned int alloc_flags)
+{
+    unsigned long watermark;
+
+    watermark = wmark_pages(zone, alloc_flags & ALLOC_WMARK_MASK);

IIUC, the watermark used in patch 8 and patch 9 is different, right? Have you measured the impact of modifying this watermark?

Actually, there is no functional change intended. Consider wmark_pages with
alloc_flags = 0 is equivalent to min_wmark_pages, patch 8 and patch 9 still
use original watermark.

Can you use ALLOC_WMARK_MIN macro to make it more clear?
Sorry, I can't quite follow this. The watermark should differ with different
alloc_flags instead of WMARK_MIN hard-coded.
Patch 8 and patch 9 use watermark with WMARK_MIN as they get alloc_flags = 0.

I mean you can pass 'alloc_flags=ALLOC_WMARK_MIN' instead of a magic number 0 when calling compaction_suit_allocation_order() in patch 8 and patch 9.

And I think patch 8 and patch 9 should be squashed into patch 7 to convert all at once.
Sure, i could do this in next version.

+    if (zone_watermark_ok(zone, order, watermark, highest_zoneidx,
+                  alloc_flags))
+        return COMPACT_SUCCESS;
+
+    if (!compaction_suitable(zone, order, highest_zoneidx))
+        return COMPACT_SKIPPED;
+
+    return COMPACT_CONTINUE;
+}
+
    static enum compact_result
    compact_zone(struct compact_control *cc, struct capture_control *capc)
    {
@@ -2390,19 +2414,11 @@ compact_zone(struct compact_control *cc, struct capture_control *capc)
        cc->migratetype = gfp_migratetype(cc->gfp_mask);
          if (compaction_with_allocation_order(cc->order)) {
-        unsigned long watermark;
-
-        /* Allocation can already succeed, nothing to do */
-        watermark = wmark_pages(cc->zone,
-                    cc->alloc_flags & ALLOC_WMARK_MASK);
-        if (zone_watermark_ok(cc->zone, cc->order, watermark,
-                      cc->highest_zoneidx, cc->alloc_flags))
-            return COMPACT_SUCCESS;
-
-        /* Compaction is likely to fail */
-        if (!compaction_suitable(cc->zone, cc->order,
-                     cc->highest_zoneidx))
-            return COMPACT_SKIPPED;
+        ret = compaction_suit_allocation_order(cc->zone, cc->order,
+                               cc->highest_zoneidx,
+                               cc->alloc_flags);
+        if (ret != COMPACT_CONTINUE)
+            return ret;
        }
          /*








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