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  1. Lustre
  2. LU-8565

sanity test 255a fails with ‘Speedup with willread is less than X%, got Y%’

    Details

    • Type: Bug
    • Status: Resolved
    • Priority: Major
    • Resolution: Fixed
    • Affects Version/s: Lustre 2.9.0
    • Fix Version/s: Lustre 2.9.0
    • Labels:
      None
    • Environment:
      autotest
    • Severity:
      3
    • Rank (Obsolete):
      9223372036854775807

      Description

      sanity test 255a fails with

      sanity test_255a: @@@@@@ FAIL: Speedup with willread is less than 88%, got 7% 
      

      where the percentage values differ for each failure.

      From one of the test failures, we can see that using the WILLREAD advice does not help with read and, for this test, does not out perform the benefits of reading from cache

      Iter 1/10: cache speedup: 98%
      Iter 1/10: ladvise speedup: -7%
      
      Iter 3/10: cache speedup: 131%
      Iter 3/10: ladvise speedup: 8%
      
      Iter 8/10: cache speedup: 108%
      Iter 8/10: ladvise speedup: 0%
      

      For this test, we are comparing the speed up gained with the WILLREAD advice versus (half) the benefit of reading from cache:

      local lowest_speedup=$((average_cache / 2))
      	[ $average_ladvise -gt $lowest_speedup ] ||
      		error "Speedup with willread is less than $lowest_speedup%,"\
      			"got $average_ladvise%"
      

      So, the expected speed up of the willread advice to ladvise is not as great as expected.

      The WILLREAD hint was added with patch http://review.whamcloud.com/#/c/12458

      Logs for recent failures are at
      https://testing.hpdd.intel.com/test_sets/3ed61acc-6d90-11e6-b058-5254006e85c2
      https://testing.hpdd.intel.com/test_sets/5eaddd70-6bca-11e6-8a8c-5254006e85c2
      https://testing.hpdd.intel.com/test_sets/f10db2be-69cf-11e6-9258-5254006e85c2
      https://testing.hpdd.intel.com/test_sets/e2c962c6-696f-11e6-9258-5254006e85c2

      Info required for matching: sanity 255a

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              • Assignee:
                lixi Li Xi (Inactive)
                Reporter:
                jamesanunez James Nunez
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                Dates

                • Created:
                  Updated:
                  Resolved: