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a8b2e30685
When sequential scrubs were merged, all calls to arc_read() (including prefetch IOs) were given ZIO_PRIORITY_ASYNC_READ. Unfortunately, this behaves badly with an existing issue where prefetch IOs cannot be re-prioritized after the issue. The result is that synchronous reads end up in the same vdev_queue as the scrub IOs and can have (in some workloads) multiple seconds of latency. This patch incorporates 2 changes. The first ensures that all scrub IOs are given ZIO_PRIORITY_SCRUB to allow the vdev_queue code to differentiate between these I/Os and user prefetches. Second, this patch introduces zio_change_priority() to provide the missing capability to upgrade a zio's priority. Reviewed by: George Wilson <george.wilson@delphix.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Tom Caputi <tcaputi@datto.com> Closes #6921 Closes #6926
83 lines
2.2 KiB
Bash
Executable File
83 lines
2.2 KiB
Bash
Executable File
#!/bin/bash
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#
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# This file and its contents are supplied under the terms of the
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# Common Development and Distribution License ("CDDL"), version 1.0.
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# You may only use this file in accordance with the terms of version
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# 1.0 of the CDDL.
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#
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# A full copy of the text of the CDDL should have accompanied this
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# source. A copy of the CDDL is also available via the Internet at
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# http://www.illumos.org/license/CDDL.
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#
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#
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# Copyright (c) 2016 by Intel, Corp.
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#
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#
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# Linux platform placeholder for collecting prefetch I/O stats
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# TBD if we can add additional kstats to achieve the desired results
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#
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zfs_kstats="/proc/spl/kstat/zfs"
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function get_prefetch_ios
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{
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typeset -l data_misses=`awk '$1 == "prefetch_data_misses" \
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{ print $3 }' $zfs_kstats/arcstats`
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typeset -l metadata_misses=`awk '$1 == "prefetch_metadata_misses" \
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{ print $3 }' $zfs_kstats/arcstats`
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typeset -l total_misses=$(( $data_misses + $metadata_misses ))
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echo $total_misses
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}
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function get_prefetched_demand_reads
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{
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typeset -l demand_reads=`awk '$1 == "demand_hit_predictive_prefetch" \
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{ print $3 }' $zfs_kstats/arcstats`
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echo $demand_reads
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}
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function get_async_upgrade_sync
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{
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typeset -l sync_wait=`awk '$1 == "async_upgrade_sync" \
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{ print $3 }' $zfs_kstats/arcstats`
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echo $sync_wait
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}
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if [ $# -ne 2 ]
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then
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echo "Usage: `basename $0` <poolname> interval" >&2
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exit 1
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fi
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poolname=$1
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interval=$2
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prefetch_ios=$(get_prefetch_ios)
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prefetched_demand_reads=$(get_prefetched_demand_reads)
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async_upgrade_sync=$(get_async_upgrade_sync)
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while true
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do
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new_prefetch_ios=$(get_prefetch_ios)
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printf "%u\n%-24s\t%u\n" $(date +%s) "prefetch_ios" \
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$(( $new_prefetch_ios - $prefetch_ios ))
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prefetch_ios=$new_prefetch_ios
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new_prefetched_demand_reads=$(get_prefetched_demand_reads)
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printf "%-24s\t%u\n" "prefetched_demand_reads" \
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$(( $new_prefetched_demand_reads - $prefetched_demand_reads ))
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prefetched_demand_reads=$new_prefetched_demand_reads
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new_async_upgrade_sync=$(get_async_upgrade_sync)
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printf "%-24s\t%u\n" "async_upgrade_sync" \
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$(( $new_async_upgrade_sync - $async_upgrade_sync ))
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async_upgrade_sync=$new_async_upgrade_sync
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sleep $interval
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done
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