linux-kernel - Re: [PATCH RFC 1/1] ocfs2: fix write IO performance improvement for high fragmentation

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Message-ID: <895c59e3-01ab-46e1-b02b-7e65a8484e1c@suse.com>
Date: Tue, 1 Apr 2025 12:47:48 +0800
From: Heming Zhao <heming.zhao@...e.com>
To: "joseph.qi@...ux.alibaba.com" <joseph.qi@...ux.alibaba.com>,
 Gautham Ananthakrishna <gautham.ananthakrishna@...cle.com>
Cc: "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
 "ocfs2-devel@...ts.linux.dev" <ocfs2-devel@...ts.linux.dev>,
 Rajesh Sivaramasubramaniom <rajesh.sivaramasubramaniom@...cle.com>,
 Junxiao Bi <junxiao.bi@...cle.com>,
 "akpm@...ux-foundation.org" <akpm@...ux-foundation.org>
Subject: Re: [PATCH RFC 1/1] ocfs2: fix write IO performance improvement for
 high fragmentation

Thank Gautham for the testing job.

Ping Joseph...
Let's quickly fix this bug.
There are two ways to fix the issue in commit 4eb7b93e0310:
- Aautham: https://lore.kernel.org/ocfs2-devel/bcce4e5c-d739-4b1c-86bd-d165ec0780be@suse.com/T/#t
- Heming: https://lore.kernel.org/ocfs2-devel/faef812f-0adc-4a46-951a-5453927c2819@suse.com/T/#t

In my view, my patch is more better.

- Heming

On 4/1/25 12:32, Gautham Ananthakrishna wrote:
> HI Heming,
> 
> I ran the tests on your patch, and it is working fine. The discontig_runner.sh was failing earlier in "Inodes Block Group Test".
> 
> Thanks,
> Gautham.
> ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
> *From:* Heming Zhao <heming.zhao@...e.com>
> *Sent:* Thursday, March 27, 2025 12:23 PM
> *To:* Gautham Ananthakrishna <gautham.ananthakrishna@...cle.com>; joseph.qi@...ux.alibaba.com <joseph.qi@...ux.alibaba.com>
> *Cc:* linux-kernel@...r.kernel.org <linux-kernel@...r.kernel.org>; ocfs2-devel@...ts.linux.dev <ocfs2-devel@...ts.linux.dev>; Rajesh Sivaramasubramaniom <rajesh.sivaramasubramaniom@...cle.com>; Junxiao Bi <junxiao.bi@...cle.com>; akpm@...ux-foundation.org <akpm@...ux-foundation.org>
> *Subject:* Re: [PATCH RFC 1/1] ocfs2: fix write IO performance improvement for high fragmentation
> On 3/27/25 14:21, Gautham Ananthakrishna wrote:
>> HI Heming,
>> 
>> Sharing the test suite may not be practical (it has shell scripts, python and C binaries). However, I can take a look into your patch and run a quick test.
>> 
>> Thanks,
>> Gautham.
>> 
> 
> Thank you for your quick reply and willingness to help.
> 
> - Heming
> ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
>> *From:* Heming Zhao <heming.zhao@...e.com>
>> *Sent:* Thursday, March 27, 2025 11:39 AM
>> *To:* Gautham Ananthakrishna <gautham.ananthakrishna@...cle.com>; joseph.qi@...ux.alibaba.com <joseph.qi@...ux.alibaba.com>
>> *Cc:* linux-kernel@...r.kernel.org <linux-kernel@...r.kernel.org>; ocfs2-devel@...ts.linux.dev <ocfs2-devel@...ts.linux.dev>; Rajesh Sivaramasubramaniom <rajesh.sivaramasubramaniom@...cle.com>; Junxiao Bi <junxiao.bi@...cle.com>; akpm@...ux-foundation.org <akpm@...ux-foundation.org>
>> *Subject:* Re: [PATCH RFC 1/1] ocfs2: fix write IO performance improvement for high fragmentation
>> Hello Gautham,
>> 
>> Thanks for locating the issue and submitting a patch.
>> Is it possible to share your test case for this bug?
>> 
>> The key of this bug is ocfs2_cluster_group_search() comparing with wrong
>> bits size. I have another fix for this bug and will send it to this mailing
>> list later.
>> 
>> Thanks,
>> Heming
>> 
>> On 3/24/25 13:48, Gautham Ananthakrishna wrote:
>>> The commit 4eb7b93e03101fd3f35e69affe566e4b1e3e3dca caused a regression
>>> in our test suite in discontig extent tests. Upon troubleshooting I found
>>> The following issues.
>>> 
>>> 1. The function ocfs2_cluster_group_search() was called for discontig allocations
>>> as well. But it checks only the contiguous bits 'bg_contig_free_bits'.
>>> It hit the ENOSPC in the following case in one of the tests.
>>> 
>>> ocfs2_mkdir()
>>>   ocfs2_reserve_new_inode()
>>>    ocfs2_reserve_suballoc_bits()
>>>     ocfs2_block_group_alloc()
>>>      ocfs2_block_group_alloc_discontig()
>>>       __ocfs2_claim_clusters()
>>>        ocfs2_claim_suballoc_bits()
>>>         ocfs2_search_chain()
>>>          ocfs2_cluster_group_search()
>>> 
>>> Looked like the commit did not consider discontig searches. To fix this,
>>> I have split ocfs2_cluster_group_search() into *_common(), *_contig() and
>>> *_discontig()
>>> 
>>> 2. That commit enforced ocfs2_cluster_group_search() to search only the
>>> 'bits_wanted' number of bits whereas ocfs2_block_group_find_clear_bits()
>>> fills the best available size and the function ocfs2_cluster_group_search()
>>> itself is supposed to search 'min_bits' at the minimum and need not be
>>> 'bits_wanted' always.
>>> 
>>> Fixed the above issues in this patch.
>>> This patch fixes 4eb7b93e03101fd3f35e69affe566e4b1e3e3dca
>>> 
>>> Signed-off-by: Gautham Ananthakrishna <gautham.ananthakrishna@...cle.com>
>>> ---
>>>   fs/ocfs2/suballoc.c | 146 ++++++++++++++++++++++++++++----------------
>>>   1 file changed, 95 insertions(+), 51 deletions(-)
>>> 
>