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  1. WiredTiger
  2. WT-9751

Fix a memory leak in reconciliation after aborted eviction

    • 8
    • Storage Engines - 2022-09-05
    • v6.0, v5.0

      We uncovered a memory leak from reconciliation, with the following signature:

      ==6758==ERROR: LeakSanitizer: detected memory leaks
      Direct leak of 9374 byte(s) in 7 object(s) allocated from:
      #0 0x4984bd in malloc
      #1 0x7ff1c5ae53e2 in __wt_malloc rc/os_common/os_alloc.c:91:14
      #2 0x7ff1c5ae5f51 in __wt_memdup src/os_common/os_alloc.c:249:5
      #3 0x7ff1c5b43229 in __rec_split_write src/reconcile/rec_write.c:2204:9
      #4 0x7ff1c5b44962 in __wt_rec_split_finish src/reconcile/rec_write.c:1706:13
      #5 0x7ff1c5b299de in __wt_rec_row_leaf src/reconcile/rec_row.c:1002:11
      #6 0x7ff1c5b3fb73 in __reconcile src/reconcile/rec_write.c:258:9
      #7 0x7ff1c5b3eeb2 in __wt_reconcile src/reconcile/rec_write.c:98:11
      #8 0x7ff1c5a596f4 in __evict_review src/evict/evict_page.c:731:9
       #9 0x7ff1c5a573e1 in __wt_evict src/evict/evict_page.c:168:5
      #10 0x7ff1c5a47b9d in __evict_page src/evict/evict_lru.c:2334:5
      #11 0x7ff1c5a4431a in __evict_lru_pages src/evict/evict_lru.c:1150:20

      The memory leak is associated with a new failpoint that was added in WT-9252 and disabled in WT-9711. The failpoint is:

      --- a/src/evict/evict_page.c
      +++ b/src/evict/evict_page.c
      @@ -760,10 +760,17 @@ __evict_review(WT_SESSION_IMPL *session, WT_REF *ref, uint32_t evict_flags, bool
             !__wt_page_is_modified(page) || LF_ISSET(WT_REC_HS | WT_REC_IN_MEMORY) ||
           /* Fail 0.1% of the time. */
           if (!closing &&
               return (EBUSY);
           return (0);

      The purview of this ticket is to:

      • Understand and fix the root cause for the memory leak
      • Restructure the code in evict_page.c to be more obvious, and introduced documented constraints if there are times when an eviction is not allowed to fail (hopefully there are none, but the cleanup is worthwhile regardless).
      • Consider updating how memory is tracked across reconciliations to ensure cleanup is obviously correct.

            chenhao.qu@mongodb.com Chenhao Qu
            alexander.gorrod@mongodb.com Alexander Gorrod
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