Re: [PATCH v1 0/5] mm/shmem: optimize read with reduced xarray lookups and folio batching

[Andrew Morton]

On Wed, 20 May 2026 18:15:33 +0800 Chi Zhiling <chizhiling@xxxxxxx> wrote:

> From: Chi Zhiling <chizhiling@xxxxxxxxxx>
> 
> This series improves shmem read performance by implementing folio
> batching in the read path and reducing unnecessary xarray lookups.
> 

Thanks.

> Performance Results
> ===================
> 
> Testing was performed with fio sequential read workloads:
> 
>   fio --ioengine=sync --rw=read --size=1G --runtime=180
> 
> 
> ### THP Disabled - Normal Files ###
> 
> | Block Size | Baseline  | v1        | Improvement |
> | ---------- | --------- | --------- | ----------- |
> | 1M         | 11.4GiB/s | 12.7GiB/s | +11.4%      |
> | 64k        | 11.2GiB/s | 12.2GiB/s | +8.9%       |
> | 4k         | 3809MiB/s | 3838MiB/s | +0.8%       |
> 
> ### THP Disabled - Fallocated Files ###
> 
> | Block Size | Baseline  | v1        | Improvement |
> | ---------- | --------- | --------- | ----------- |
> | 1M         | 23.7GiB/s | 28.7GiB/s | +21.1%      |
> | 64k        | 22.6GiB/s | 27.0GiB/s | +19.5%      |
> | 4k         | 4668MiB/s | 4678MiB/s | +0.2%       |
> 
> ### THP Enabled - Normal Files ###
> 
> | Block Size | Baseline  | v1        | Improvement |
> | ---------- | --------- | --------- | ----------- |
> | 1M         | 13.9GiB/s | 13.9GiB/s | 0%          |
> | 64k        | 13.4GiB/s | 13.4GiB/s | 0%          |
> | 4k         | 3818MiB/s | 3836MiB/s | +0.5%       |
> 
> ### THP Enabled - Fallocated Files ###
> 
> | Block Size | Baseline  | v1        | Improvement |
> | ---------- | --------- | --------- | ----------- |
> | 1M         | 24.1GiB/s | 34.9GiB/s | +44.8%      |
> | 64k        | 22.9GiB/s | 31.3GiB/s | +36.7%      |
> | 4k         | 4721MiB/s | 4708MiB/s | -0.3%       |

That looks nice.

AI review might have found a few things:
	https://sashiko.dev/#/patchset/20260520101538.58745-1-chizhiling@xxxxxxx

I'll skip the patchset for now (unreviewed v1!).