linux-kernel - Re: [PATCH v5] block: move non sync requests complete flow to softirq

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Message-ID: <cf7e9e40-dcd3-4bcd-8bf5-fc1d594afae6@kernel.dk>
Date: Fri, 6 Sep 2024 07:35:38 -0600
From: Jens Axboe <axboe@...nel.dk>
To: ZhangHui <zhanghui31@...omi.com>, bvanassche@....org,
 ming.lei@...hat.com, dlemoal@...nel.org
Cc: linux-block@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5] block: move non sync requests complete flow to softirq

On 9/6/24 3:54 AM, ZhangHui wrote:
> From: zhanghui <zhanghui31@...omi.com>
> 
> Currently, for a controller that supports multiple queues, like UFS4.0,
> the mq_ops->complete is executed in the interrupt top-half. Therefore, 
> the file system's end io is executed during the request completion process,
> such as f2fs_write_end_io on smartphone.
> 
> However, we found that the execution time of the file system end io
> is strongly related to the size of the bio and the processing speed
> of the CPU. Because the file system's end io will traverse every page
> in bio, this is a very time-consuming operation.
> 
> We measured that the 80M bio write operation on the little CPU will
> cause the execution time of the top-half to be greater than 100ms,
> which will undoubtedly affect interrupt response latency.
> 
> Let's fix this issue by moving non sync requests completion to softirq
> context, and keeping sync requests completion in the IRQ top-half context.

Didn't we already conclude that the fix for this would be on the f2fs
side?

-- 
Jens Axboe