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Requests that triggers flushing volatile writeback cache to disk (barriers) have significant effect to overall performance. Block layer has sophisticated engine for combining several flush requests into one. But there is no statistics for actual flushes executed by disk. Requests which trigger flushes usually are barriers - zero-size writes. This patch adds two iostat counters into /sys/class/block/$dev/stat and /proc/diskstats - count of completed flush requests and their total time. Signed-off-by: Konstantin Khlebnikov <khlebnikov@yandex-team.ru> Signed-off-by: Jens Axboe <axboe@kernel.dk>
38 lines
1007 B
Plaintext
38 lines
1007 B
Plaintext
What: /proc/diskstats
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Date: February 2008
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Contact: Jerome Marchand <jmarchan@redhat.com>
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Description:
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The /proc/diskstats file displays the I/O statistics
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of block devices. Each line contains the following 14
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fields:
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1 - major number
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2 - minor mumber
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3 - device name
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4 - reads completed successfully
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5 - reads merged
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6 - sectors read
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7 - time spent reading (ms)
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8 - writes completed
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9 - writes merged
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10 - sectors written
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11 - time spent writing (ms)
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12 - I/Os currently in progress
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13 - time spent doing I/Os (ms)
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14 - weighted time spent doing I/Os (ms)
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Kernel 4.18+ appends four more fields for discard
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tracking putting the total at 18:
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15 - discards completed successfully
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16 - discards merged
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17 - sectors discarded
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18 - time spent discarding
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Kernel 5.5+ appends two more fields for flush requests:
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19 - flush requests completed successfully
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20 - time spent flushing
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For more details refer to Documentation/admin-guide/iostats.rst
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