Re: [PATCH 1/2] xfs/078: disable all concurrency scaling

On 6/18/26 8:54 AM, Eric Sandeen wrote:
> On 6/18/26 8:48 AM, Christoph Hellwig wrote:
>> Disable concurrency scaling to avoid mismatching output on systems with
>> a large CPU count.
>>
>> Reported-by: Shin'ichiro Kawasaki <[email protected]>
>> Signed-off-by: Christoph Hellwig <[email protected]>
> 
> I think this papers over what I still feel is a problem in mkfs.xfs
> behavior, but that's a different issue and making tests pass is good, so:
> 
> Reviewed-by: Eric Sandeen <[email protected]>

Er, hang on - let me retract that. Lukas sent a series to address
this problem too, right, and one of the things he added in his series
is a helper to determine whether the concurrency options even exist,
so that this can continue to run on older xfsprogs, which seems like
a good idea, no?

https://git.kernel.org/pub/scm/fs/xfs/xfstests-dev.git/commit/?h=for-next&id=7f162f5bcf50fc32c7e3b432e7ff189571a3151f

which added _scratch_mkfs_xfs_supports_concurrency()

>> ---
>>  tests/xfs/078 | 8 +++++---
>>  1 file changed, 5 insertions(+), 3 deletions(-)
>>
>> diff --git a/tests/xfs/078 b/tests/xfs/078
>> index 6057aeea12ab..8ef52614b125 100755
>> --- a/tests/xfs/078
>> +++ b/tests/xfs/078
>> @@ -57,9 +57,11 @@ _grow_loop()
>>  	$XFS_IO_PROG -f -c "truncate $original" $LOOP_IMG
>>  	loop_dev=`_create_loop_device $LOOP_IMG $bsize`
>>  
>> -	dparam=""
>> +	# Disable concurrency scaling to avoid output differences due to large
>> +	# CPU counts.
>> +	mkfs_opts="-d concurrency=0 -l concurrency=0 -r concurrency=0"
>>  	if [ -n "$agsize" ]; then
>> -		dparam="-d agsize=$agsize"
>> +		mkfs_opts="$mkfs_opts -d agsize=$agsize"
>>  	fi
>>  
>>  	echo
>> @@ -67,7 +69,7 @@ _grow_loop()
>>  	echo
>>  
>>  	echo "*** mkfs loop file (size=$original)"
>> -	$MKFS_XFS_PROG -b size=$bsize $dparam $loop_dev | \
>> +	$MKFS_XFS_PROG -b size=$bsize $mkfs_opts $loop_dev | \
>>  		_filter_mkfs 2>/dev/null
>>  
>>  	echo "*** extend loop file"
> 
>