Re: btrfs write-bandwidth performance regression of 6.5-rc4/rc3

["Linux regression tracking (Thorsten Leemhuis)" <regressions@leemhuis.info>]

On 13.08.23 11:50, Wang Yugui wrote:
>> On 8/11/23 10:23 AM, Wang Yugui wrote:
>>>> On Wed, Aug 02, 2023 at 08:04:57AM +0800, Wang Yugui wrote:
>>>>>> And with only a revert of
>>>>>>
>>>>>> "btrfs: submit IO synchronously for fast checksum implementations"?
>>>>> GOOD performance when only (Revert "btrfs: submit IO synchronously for fast
>>>>> checksum implementations") 
>>>> Ok, so you have a case where the offload for the checksumming generation
>>>> actually helps (by a lot).  Adding Chris to the Cc list as he was
>>>> involved with this.
>>>>
>>>>>>> -       if (test_bit(BTRFS_FS_CSUM_IMPL_FAST, &bbio->fs_info->flags))
>>>>>>> +       if ((bbio->bio.bi_opf & REQ_META) && test_bit(BTRFS_FS_CSUM_IMPL_FAST, &bbio->fs_info->flags))
>>>>>>>                 return false;
>>>>>> This disables synchronous checksum calculation entirely for data I/O.
>>>>> without this fix, data I/O checksum is always synchronous?
>>>>> this is a feature change of "btrfs: submit IO synchronously for fast checksum implementations"?
>>>> It is never with the above patch.
>>>>
>>>>>> Also I'm curious if you see any differents for a non-RAID0 (i.e.
>>>>>> single profile) workload.
>>>>> '-m single -d single' is about 10% slow that '-m raid1 -d raid0' in this test
>>>>> case.
>>>> How does it compare with and without the revert?  Can you add the numbers?
>>
>> Looking through the thread, you're comparing -m single -d single, but
>> btrfs is still doing the raid.
>>
>> Sorry to keep asking for more runs, but these numbers are a surprise,
>> and I probably won't have time today to reproduce before vacation next
>> week (sadly, Christoph and I aren't going together).

Sadly I also did not run into either you or Christoph during my own
vacation during the last two weeks. But I'm back from it how, which got
me wondering:

What happened to this regression? Was any progress made to resolve this
in one way or another?

Ciao, Thorsten (wearing his 'the Linux kernel's regression tracker' hat)
--
Everything you wanna know about Linux kernel regression tracking:
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#regzbot poke

>> Can you please do a run where lvm or MD raid are providing the raid0?
> no LVM/MD used here.
> 
>> It doesn't look like you're using compression, but I wanted to double check.
> 
> Yes. '-m xx -d yy' with other default mkfs.btrfs option, so no compression.
> 
>> How much ram do you have?
> 
> 192G ECC memory.
> 
> two CPU numa nodes, but all PCIe3 NVMe SSD are connected to one NVMe HBA/
> one numa node.
> 
>> Your fio run has 4 jobs going, can I please see the full fio output for
>> a fast run and a slow run?
> 
> fio results are saved into attachment files (fast.text & slow.txt)
> 
> Best Regards
> Wang Yugui (wangyugui@e16-tech.com)
> 2023/08/13