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  1. MariaDB Server
  2. MDEV-25113

Reduce effect of parallel background flush on select workload

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      Description

      Let's say the pattern of workload involves read-write workload followed by read-only workload.

      Read-write workload modifies pages that would cause background flushing to get active and flush dirty pages. This action of flushing dirty pages continues till the dirty_pct < innodb_max_dirty_pages_pct_lwm. This means even post read-write workload when the read-only workload starts background flushing could remain active.

      This could affect the overall throughput of the select workload.

      This task is meant to explore if there is a possibility to reduce the effect of background flush on active select workload (94-?93->92->91).

      -----------

      In the example below for the first 14 secs, adaptive flushing is active and post that there is no flushing taking place. As we could tps have a bit of noise in the first part.

      Example:

      [ 1s ] thds: 8 tps: 5864.27 qps: 93922.16 (r/w/o: 82185.64/0.00/11736.53) lat (ms,95%): 1.44 err/s: 0.00 reconn/s: 0.00
      [ 2s ] thds: 8 tps: 5878.06 qps: 94032.93 (r/w/o: 82276.81/0.00/11756.12) lat (ms,95%): 1.44 err/s: 0.00 reconn/s: 0.00
      [ 3s ] thds: 8 tps: 5901.05 qps: 94402.87 (r/w/o: 82601.76/0.00/11801.11) lat (ms,95%): 1.44 err/s: 0.00 reconn/s: 0.00
      [ 4s ] thds: 8 tps: 5822.01 qps: 93179.09 (r/w/o: 81534.08/0.00/11645.01) lat (ms,95%): 1.44 err/s: 0.00 reconn/s: 0.00
      [ 5s ] thds: 8 tps: 5754.02 qps: 92043.27 (r/w/o: 80535.24/0.00/11508.03) lat (ms,95%): 1.47 err/s: 0.00 reconn/s: 0.00
      [ 6s ] thds: 8 tps: 5682.98 qps: 90906.72 (r/w/o: 79540.76/0.00/11365.97) lat (ms,95%): 1.52 err/s: 0.00 reconn/s: 0.00
      [ 7s ] thds: 8 tps: 5698.98 qps: 91228.70 (r/w/o: 79830.74/0.00/11397.96) lat (ms,95%): 1.52 err/s: 0.00 reconn/s: 0.00
      [ 8s ] thds: 8 tps: 5688.00 qps: 90974.05 (r/w/o: 79598.04/0.00/11376.01) lat (ms,95%): 1.52 err/s: 0.00 reconn/s: 0.00
      [ 9s ] thds: 8 tps: 5641.97 qps: 90312.57 (r/w/o: 79028.62/0.00/11283.95) lat (ms,95%): 1.52 err/s: 0.00 reconn/s: 0.00
      [ 10s ] thds: 8 tps: 5695.03 qps: 91104.54 (r/w/o: 79714.48/0.00/11390.07) lat (ms,95%): 1.50 err/s: 0.00 reconn/s: 0.00
      [ 11s ] thds: 8 tps: 5736.92 qps: 91757.79 (r/w/o: 80283.94/0.00/11473.85) lat (ms,95%): 1.50 err/s: 0.00 reconn/s: 0.00
      [ 12s ] thds: 8 tps: 5692.11 qps: 91080.74 (r/w/o: 79696.52/0.00/11384.22) lat (ms,95%): 1.52 err/s: 0.00 reconn/s: 0.00
      [ 13s ] thds: 8 tps: 5691.95 qps: 91085.15 (r/w/o: 79701.26/0.00/11383.89) lat (ms,95%): 1.55 err/s: 0.00 reconn/s: 0.00
      [ 14s ] thds: 8 tps: 5692.04 qps: 91082.60 (r/w/o: 79698.53/0.00/11384.08) lat (ms,95%): 1.55 err/s: 0.00 reconn/s: 0.00

      [ 15s ] thds: 8 tps: 5775.99 qps: 92398.80 (r/w/o: 80846.82/0.00/11551.97) lat (ms,95%): 1.50 err/s: 0.00 reconn/s: 0.00
      [ 16s ] thds: 8 tps: 5828.96 qps: 93266.41 (r/w/o: 81608.49/0.00/11657.93) lat (ms,95%): 1.50 err/s: 0.00 reconn/s: 0.00
      [ 17s ] thds: 8 tps: 5835.04 qps: 93376.59 (r/w/o: 81706.52/0.00/11670.07) lat (ms,95%): 1.47 err/s: 0.00 reconn/s: 0.00
      [ 18s ] thds: 8 tps: 5810.96 qps: 92941.38 (r/w/o: 81320.46/0.00/11620.92) lat (ms,95%): 1.50 err/s: 0.00 reconn/s: 0.00
      [ 19s ] thds: 8 tps: 5834.05 qps: 93358.84 (r/w/o: 81689.73/0.00/11669.10) lat (ms,95%): 1.50 err/s: 0.00 reconn/s: 0.00
      [ 20s ] thds: 8 tps: 5836.97 qps: 93387.55 (r/w/o: 81713.60/0.00/11673.94) lat (ms,95%): 1.50 err/s: 0.00 reconn/s: 0.00
      [ 21s ] thds: 8 tps: 5836.97 qps: 93425.60 (r/w/o: 81751.65/0.00/11673.95) lat (ms,95%): 1.47 err/s: 0.00 reconn/s: 0.00
      [ 22s ] thds: 8 tps: 5839.98 qps: 93424.69 (r/w/o: 81745.73/0.00/11678.96) lat (ms,95%): 1.50 err/s: 0.00 reconn/s: 0.00
      [ 23s ] thds: 8 tps: 5838.04 qps: 93412.72 (r/w/o: 81735.63/0.00/11677.09) lat (ms,95%): 1.50 err/s: 0.00 reconn/s: 0.00

        Attachments

        1. 25113-fix2.png
          71 kB
          Alexander Krizhanovsky
        2. MDEV-25113.patch
          11 kB
          Alexander Krizhanovsky
        3. tpcc_10.6_1h_multi.png
          66 kB
          Marko Mäkelä
        4. tpcc_10.6_1h_pct_lwn10ppct30_io1020x88_new.png
          31 kB
          Alexander Krizhanovsky
        5. tpcc_10.6_bp25g_io.png
          46 kB
          Alexander Krizhanovsky

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              Assignee:
              marko Marko Mäkelä
              Reporter:
              krunalbauskar Krunal Bauskar
              Votes:
              1 Vote for this issue
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                Updated:
                Resolved:

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