linux-ext4 - Re: ext2/zram issue [was: Linux 5.19]

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Date:   Tue, 9 Aug 2022 21:57:50 +0900
From:   Sergey Senozhatsky <senozhatsky@...omium.org>
To:     Jiri Slaby <jirislaby@...nel.org>
Cc:     Sergey Senozhatsky <senozhatsky@...omium.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        minchan@...nel.org, ngupta@...are.org, Jan Kara <jack@...e.com>,
        Ted Ts'o <tytso@....edu>,
        Andreas Dilger <adilger.kernel@...ger.ca>,
        Ext4 Developers List <linux-ext4@...r.kernel.org>,
        avromanov@...rdevices.ru, ddrokosov@...rdevices.ru
Subject: Re: ext2/zram issue [was: Linux 5.19]

On (22/08/09 14:45), Jiri Slaby wrote:
> On 09. 08. 22, 14:35, Jiri Slaby wrote:
> > But the installer is different. It just creates memory pressure, yet,
> > reclaim works well and is able to find memory and go on. I would say
> > atomic vs non-atomic retry in the original (pre-5.19) approach makes the
> > difference.
> 
> Sorry, I meant no-direct-reclaim (5.19) vs direct-reclaim (pre-5.19).

Sure, I understood.

This somehow makes me scratch my head and ask if we really want to
continue using per-CPU steams. We previously (many years ago) had
a list of idle compression streams, which would do compression in
preemptible context and we would have only one zs_malloc handle
allocation path, which would do direct reclaim (when needed)