Re: [PATCH v2 00/16] Parallelizing filesystem writeback

Kundan Kumar
2025-10-29T06:05:56Z

On 10/22/2025 10:09 AM, Christoph Hellwig wrote:
> On Tue, Oct 21, 2025 at 09:46:30AM +1100, Dave Chinner wrote:
>> Not necessarily. The allocator can (and will) select different AGs
>> for an inode as the file grows and the AGs run low on space. Once
>> they select a different AG for an inode, they don't tend to return
>> to the original AG because allocation targets are based on
>> contiguous allocation w.r.t. existing adjacent extents, not the AG
>> the inode is located in.
>
> Also, as pointed out in the last discussion of this for the RT
> subvolume there is zero relation between the AG the inode is in
> and the data placement.
>
>
I evaluated the effect of parallel writeback on realtime inodes and
observed no improvement in IOPS. We can limit writes for realtime
inodes to utilize a single default (0) writeback context. Do you
see it differently?