From: "Theodore Ts'o" <tytso@mit.edu>
To: Andi Kleen <ak@linux.intel.com>
Cc: libaokun1@huawei.com, linux-ext4@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH v3 01/17] ext4: add ext4_try_lock_group() to skip busy groups
Date: Thu, 17 Jul 2025 23:09:32 -0400 [thread overview]
Message-ID: <20250718030932.GE112967@mit.edu> (raw)
In-Reply-To: <87pldy78qc.fsf@linux.intel.com>
On Thu, Jul 17, 2025 at 03:28:27PM -0700, Andi Kleen wrote:
>
> It seems this makes block allocation non deterministic, but depend on
> the system load. I can see where this could cause problems when
> reproducing bugs at least, but perhaps also in other cases.
>
> Better perhaps just round robin the groups?
> Or at least add a way to turn it off.
Ext4 has never guareanteed deterministic allocation; in particular,
there are times when we using get_random_u32 whens selecting the block
group used when allocating a new inode, and since the block alocation
is based on block group of the inode, therefore the block allocation
isn't deterministic.
In any case, given there many workloads are doing multi-threaded
allocations, in practice, even without these calls to get_random,
things tend not to be deterministic anyway.
- Ted
next prev parent reply other threads:[~2025-07-18 3:09 UTC|newest]
Thread overview: 44+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-07-14 13:03 [PATCH v3 00/17] ext4: better scalability for ext4 block allocation Baokun Li
2025-07-14 13:03 ` [PATCH v3 01/17] ext4: add ext4_try_lock_group() to skip busy groups Baokun Li
2025-07-17 10:09 ` Ojaswin Mujoo
2025-07-19 0:37 ` Baokun Li
2025-07-17 22:28 ` Andi Kleen
2025-07-18 3:09 ` Theodore Ts'o [this message]
2025-07-19 0:29 ` Baokun Li
2025-07-22 20:59 ` Andi Kleen
2025-07-14 13:03 ` [PATCH v3 02/17] ext4: separate stream goal hits from s_bal_goals for better tracking Baokun Li
2025-07-17 10:29 ` Ojaswin Mujoo
2025-07-19 1:37 ` Baokun Li
2025-07-14 13:03 ` [PATCH v3 03/17] ext4: remove unnecessary s_mb_last_start Baokun Li
2025-07-17 10:31 ` Ojaswin Mujoo
2025-07-14 13:03 ` [PATCH v3 04/17] ext4: remove unnecessary s_md_lock on update s_mb_last_group Baokun Li
2025-07-17 13:36 ` Ojaswin Mujoo
2025-07-19 1:54 ` Baokun Li
2025-07-14 13:03 ` [PATCH v3 05/17] ext4: utilize multiple global goals to reduce contention Baokun Li
2025-07-14 13:03 ` [PATCH v3 06/17] ext4: get rid of some obsolete EXT4_MB_HINT flags Baokun Li
2025-07-14 13:03 ` [PATCH v3 07/17] ext4: fix typo in CR_GOAL_LEN_SLOW comment Baokun Li
2025-07-14 13:03 ` [PATCH v3 08/17] ext4: convert sbi->s_mb_free_pending to atomic_t Baokun Li
2025-07-14 13:03 ` [PATCH v3 09/17] ext4: merge freed extent with existing extents before insertion Baokun Li
2025-07-14 13:03 ` [PATCH v3 10/17] ext4: fix zombie groups in average fragment size lists Baokun Li
2025-07-14 13:03 ` [PATCH v3 11/17] ext4: fix largest free orders lists corruption on mb_optimize_scan switch Baokun Li
2025-07-14 13:03 ` [PATCH v3 12/17] ext4: factor out __ext4_mb_scan_group() Baokun Li
2025-07-14 13:03 ` [PATCH v3 13/17] ext4: factor out ext4_mb_might_prefetch() Baokun Li
2025-07-14 13:03 ` [PATCH v3 14/17] ext4: factor out ext4_mb_scan_group() Baokun Li
2025-07-14 13:03 ` [PATCH v3 15/17] ext4: convert free groups order lists to xarrays Baokun Li
2025-07-21 11:07 ` Jan Kara
2025-07-21 12:33 ` Baokun Li
2025-07-21 13:45 ` Baokun Li
2025-07-21 18:01 ` Theodore Ts'o
2025-07-22 5:58 ` Baokun Li
2025-07-24 3:55 ` Guenter Roeck
2025-07-24 4:54 ` Theodore Ts'o
2025-07-24 5:20 ` Guenter Roeck
2025-07-24 11:14 ` Zhang Yi
2025-07-24 14:30 ` Guenter Roeck
2025-07-24 14:54 ` Theodore Ts'o
2025-07-25 2:28 ` Zhang Yi
2025-07-26 0:50 ` Baokun Li
2025-07-14 13:03 ` [PATCH v3 16/17] ext4: refactor choose group to scan group Baokun Li
2025-07-14 13:03 ` [PATCH v3 17/17] ext4: implement linear-like traversal across order xarrays Baokun Li
2025-07-15 1:11 ` [PATCH v3 00/17] ext4: better scalability for ext4 block allocation Zhang Yi
2025-07-19 21:45 ` Theodore Ts'o
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