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apfstests/tests/btrfs/181
T
Filipe Manana 8c16b061f7 btrfs: make all btrfs tests that exercise balance use _run_btrfs_balance_start()
In btrfs-progs v4.10 we had a behaviour change where starting a balance
operation without any filters results in a delay of 10 seconds and a
warning is printed to stdout that warns that a full balance is about to
be made and that it can be a slow operation. The new flag '--full-balance'
was added in that release to avoid the 10 seconds delay and the warning
message.

Our existing helper _run_btrfs_balance_start() uses that new balance flag
if we are running a btrfs-progs version that has it, to avoid that 10
seconds wait.

Make all existing btrfs tests that trigger balance operations use the
_run_btrfs_balance_start() helper, so that we avoid wasting time and
speed up some of the tests. In particular test btrfs/014 is now about 10x
faster and tests btrfs/060 to btrfs/064 3 to 5 times faster (depending
on the fsstress random load).

Besides speeding up many tests that do balance operations it also fixes
functional problems:

1) Since btrfs-progs v4.10 the test case btrfs/014 got broken, because
   its purpose is to run balance and snapshot creation in parallel,
   and that wasn't happening anymore because all snapshots were being
   created during the 10 seconds delay of the first balance operation,
   so balance and snapshot creation was being serialized instead of
   running in parallel.

   Fixing this test to avoid the 10 seconds delay immediately
   exposes a regression that went into kernel 5.7-rc1 which is fixed
   by the following commit

   aec7db3b13a0 ("btrfs: fix setting last_trans for reloc roots")

2) Test cases btrfs/060 to btrfs/064 now spend much more time running
   fsstress, balance and other operations in parallel, there's no
   longer intervals of 10 seconds where balance is not running
   concurrently with those other operations, making the tests a lot
   more useful again.

Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: Eryu Guan <guaneryu@gmail.com>
Signed-off-by: Eryu Guan <guaneryu@gmail.com>
2020-04-20 00:40:59 +08:00

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#! /bin/bash
# SPDX-License-Identifier: GPL-2.0
# Copyright (C) 2019 SUSE Linux Products GmbH. All Rights Reserved.
#
# FS QA Test 181
#
# Test if btrfs will commit too many transactions for nothing and cause
# performance regression during balance.
#
# This bug is going to be fixed by a patch for kernel title
# "btrfs: don't end the transaction for delayed refs in throttle"
#
seq=`basename $0`
seqres=$RESULT_DIR/$seq
echo "QA output created by $seq"
here=`pwd`
tmp=/tmp/$$
status=1 # failure is the default!
trap "_cleanup; exit \$status" 0 1 2 3 15
_cleanup()
{
cd /
rm -f $tmp.*
}
# get standard environment, filters and checks
. ./common/rc
. ./common/filter
# remove previous $seqres.full before test
rm -f $seqres.full
# real QA test starts here
# Modify as appropriate.
_supported_fs btrfs
_supported_os Linux
_require_scratch
_require_btrfs_command inspect-internal dump-super
_scratch_mkfs > /dev/null
_scratch_mount
nr_files=1024
get_super_gen()
{
local ret=$($BTRFS_UTIL_PROG inspect dump-super "$SCRATCH_DEV" |\
grep ^generation | awk '{print $2}')
if [ -z $ret ]; then
_fail "failed to get super block generation"
fi
echo "$ret"
}
$BTRFS_UTIL_PROG subvolume create "$SCRATCH_MNT/subvol" > /dev/null
# Create some small files to take up enough metadata reserved space
for ((i = 0; i < $nr_files; i++)) do
_pwrite_byte 0xcd 0 1K "$SCRATCH_MNT/subvol/file_$i" > /dev/null
done
# Commit the fs so we can get a stable super generation
sync
before_gen=$(get_super_gen)
_run_btrfs_balance_start -m $SCRATCH_MNT >> $seqres.full
after_gen=$(get_super_gen)
# Since the fs is pretty small, we should have only 1 small metadata chunk and
# one tiny system chunk.
# Relocating such small chunks only needs 6 commits for each, thus 12 commits for
# 2 chunks.
# Here we use 10x the theoretic value as threshold.
theoretic_gen=$(( 6 * 2 ))
threshold_gen=$(( 10 * $theoretic_gen ))
if [ $(( $after_gen - $before_gen )) -gt 120 ]; then
echo "balance committed too many transactions"
echo "super generation before balance: ${before_gen}"
echo "super generation after balance: ${after_gen}"
echo "super generation difference: $((after_gen - before_gen))"
echo "theoretic generation difference: ${theoretic_gen}"
echo "threshold generation difference: ${threshold_gen}"
fi
echo "super generation before balance: ${before_gen}" >> $seqres.full
echo "super generation after balance: ${after_gen}" >> $seqres.full
echo "super generation difference: $((after_gen - before_gen))" >> $seqres.full
echo "theoretic generation difference: ${theoretic_gen}" >> $seqres.full
echo "threshold generation difference: ${threshold_gen}" >> $seqres.full
# success, all done
echo "Silence is golden"
status=0
exit