On 2018年03月28日 14:19, Eryu Guan wrote:
> On Wed, Mar 28, 2018 at 01:51:44PM +0800, Qu Wenruo wrote:
>>
>>
>> On 2018年03月28日 13:04, Amir Goldstein wrote:
>>> On Wed, Mar 28, 2018 at 7:40 AM, Qu Wenruo <wqu@xxxxxxxx> wrote:
>>>> Basic test case which triggers fsstress with dm-log-writes, and then
>>>> check the fs after each FUA writes.
>>>> With needed infrastructure and special handlers for journal based fs.
>>>>
>>>> Signed-off-by: Qu Wenruo <wqu@xxxxxxxx>
>>>> ---
>>>> changelog:
>>>> v2:
>>>> Use proper "SUSE Linux Products GmbH" instead of "SuSE"
>>>> Get rid of dm-snapshot which is pretty slow if we're creating and
>>>> deleting snapshots repeatedly.
>>>> (Maybe LVM thin provision would be much better, but current replay
>>>> solution is good so far, and no slower than dm-snapshot)
>>>> Add back run_check so that we can get the seed.
>>>> ---
>>>> Unfortunately, neither xfs nor ext4 survies this test for even single
>>>> success, while btrfs survives.
>>>> (Although not what I want, I'm just trying my luck
>>>> to reproduce a serious btrfs corruption situation)
>>>>
>>>> Although btrfs may be the fastest fs for the test, since it has fixed
>>>> small amount of write in mkfs and almost nothing to replay, it still
>>>> takes about 240s~300s to finish (the same level using snapshot).
>>>>
>>>> It would take longer time for ext4 for its large amount of write during
>>>> mkfs, if it can survive the test in the first space.
>>>
>>> Hmm, how much time would the total test would take if you don't fail
>>> it on fsck? I am asking because it may be possible to improve this with
>>> only a single snapshot after mkfs.
>>
>> The only fs which can pass the test right now is btrfs, so other
>> estimation is mostly based on guess.
>>
>>>
>>> Anyway, if total test run time is expected to be under 10min I wouldn't
>>> bother with this optimization, at least not right now. IMO it is more
>>> important to get the test out there to get the corruption bugs floating.
>>
>> I'd say from current status, if XFS doesn't fail, it would definitely
>> finish in 10min.
>> For EXT4 I'm not pretty sure.
>
> 10min might be a bit long, 5min would be good enough. I may need to
> adjust the fsstress "-n" param based on test results when I got some
> time, hopefully this week..
>
> And I noticed that fsstress "-p" is based on nr_cpus, I'd like to cap it
> with a max allowed number, so test won't run for too long on hosts with
> hundreds of cpus. It could always be scaled with _scale_fsstress_args.
>
> +nr_cpus=$("$here/src/feature" -o)
> +fsstress_args=$(_scale_fsstress_args -w -d $SCRATCH_MNT -n 512 -p $nr_cpus \
> + $FSSTRESS_AVOID)
This makes sense.
(I used to think 4 cores was enough and now mainstream desktop is push 8
cores)
Thanks,
Qu
>
>>
>> I'd like to keep current test case as simple as possible right now, and
>> for later enhancement, I have several different ideas:
>
> Please make new tests then :)
>
>>
>> 1) Reflink fs + loopback
>> Yep, use btrfs/xfs as base filesystem and create copy using reflink,
>> then use such files as loopback device.
>> The good thing is, AFAIK btrfs/xfs reflink is really fast.
>> Much much faster than dm-snapshot or even LVM thin.
>>
>> The much much smaller block size (4K default) makes CoW overhead
>> (LVM thin is 64K, not sure about dm-snapshot though).
>>
>> The problem is, such setup needs extra mount point and can be a
>> little hard to setup, and we're introducing another layer of fs,
>> if the fs itself has some hidden bug, it would screw up the test
>> case.
>>
>> 2) LVM thin provision
>> LVM thin provision looks much like btrfs/xfs for block level, and
>> smaller default block size (64K vs original 2M) makes CoW overhead
>> smaller.
>>
>> I'm currently testing this method, the good thing is it's a little
>> easier to setup and we can use single mount point.
>>
>> Anyway, with proper and efficient snapshot ability implemented, I will
>> definitely convert this test case, and add Flush test case.
>>
>> Thanks for your review too,
>> Qu
>>
>>>
>>> Thanks for working on this!
>>> You can add
>>> Reviewed-by: Amir Goldstein <amir73il@xxxxxxxxx>
>
> Thank you both!
>
> Eryu
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