linux-kernel - Re: [PATCH 00/11] md: avoid counter operation conflicts

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Message-ID: <481dc71231494b729b13dcc7392deb00@kioxia.com>
Date: Wed, 27 Mar 2024 01:27:19 +0000
From: tada keisuke <keisuke1.tada@...xia.com>
To: Yu Kuai <yukuai1@...weicloud.com>, "song@...nel.org" <song@...nel.org>
CC: "linux-raid@...r.kernel.org" <linux-raid@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "yukuai (C)"
	<yukuai3@...wei.com>
Subject: Re: [PATCH 00/11] md: avoid counter operation conflicts

>> Currently, active_aligned_reads and nr_pending used as counters are atomic types.
>> Therefore, when inc/dec in a multi-core results in conflicts.
>
> I don't uderstand what's the problem here, what's wrong with atomic
> types in a multi-core system?

Hi Kuai

This patch is not a fix for the problem, but an improvement.
This patch makes the counter inc/dec faster.

For the same reason, active_io was changed from atomic_t to percpu_ref.
https://marc.info/?l=linux-raid&m=167514225920879

Thanks,
Keisuke