linux-kernel - Re: [f2fs-dev] [PATCH 2/2] f2fs: handle decompress only post processing in softirq

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Message-ID: <YrEXmiRH+DcbW2EI@B-P7TQMD6M-0146.local>
Date:   Tue, 21 Jun 2022 08:58:02 +0800
From:   Gao Xiang <hsiangkao@...ux.alibaba.com>
To:     Daeho Jeong <daeho43@...il.com>
Cc:     linux-kernel@...r.kernel.org,
        linux-f2fs-devel@...ts.sourceforge.net, kernel-team@...roid.com,
        Daeho Jeong <daehojeong@...gle.com>
Subject: Re: [f2fs-dev] [PATCH 2/2] f2fs: handle decompress only post
 processing in softirq

On Mon, Jun 20, 2022 at 10:38:43AM -0700, Daeho Jeong wrote:
> From: Daeho Jeong <daehojeong@...gle.com>
> 
> Now decompression is being handled in workqueue and it makes read I/O
> latency non-deterministic, because of the non-deterministic scheduling
> nature of workqueues. So, I made it handled in softirq context only if
> possible, not in low memory devices, since this modification will
> maintain decompresion related memory a little longer.
> 

Again, I don't think this method scalable.  Since you already handle
all decompression algorithms in this way.  Laterly, I wonder if you'd
like to handle all:
 - decompression algorithms;
 - verity algorithms;
 - decrypt algorithms;

in this way, regardless of slow decompression algorithms, that would be a
long latency and CPU overhead of softirq context.  This is my last words
on this, I will not talk anymore.

Thanks,
Gao Xiang