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From: Andrew Morton <akpm@linux-foundation.org>
To: Minchan Kim <minchan@kernel.org>
Cc: LKML <linux-kernel@vger.kernel.org>,
	Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>,
	Joey Pabalinas <joeypabalinas@gmail.com>
Subject: Re: [PATCH v3 5/7] zram: support idle/huge page writeback
Date: Wed, 28 Nov 2018 15:35:59 -0800
Message-ID: <20181128153559.f6645b98a7033b6f6f6b0fbc@linux-foundation.org> (raw)
In-Reply-To: <20181127055429.251614-6-minchan@kernel.org>

On Tue, 27 Nov 2018 14:54:27 +0900 Minchan Kim <minchan@kernel.org> wrote:

> This patch supports new feature "zram idle/huge page writeback".
> On zram-swap usecase, zram has usually many idle/huge swap pages.
> It's pointless to keep in memory(ie, zram).
> 
> To solve the problem, this feature introduces idle/huge page
> writeback to backing device so the goal is to save more memory
> space on embedded system.
> 
> Normal sequence to use idle/huge page writeback feature is as follows,
> 
> while (1) {
>         # mark allocated zram slot to idle
>         echo all > /sys/block/zram0/idle
>         # leave system working for several hours
>         # Unless there is no access for some blocks on zram,
> 	# they are still IDLE marked pages.
> 
>         echo "idle" > /sys/block/zram0/writeback
> 	or/and
> 	echo "huge" > /sys/block/zram0/writeback
>         # write the IDLE or/and huge marked slot into backing device
> 	# and free the memory.
> }
> 
> By per discussion:
> https://lore.kernel.org/lkml/20181122065926.GG3441@jagdpanzerIV/T/#u,
> 
> This patch removes direct incommpressibe page writeback feature
> (d2afd25114f4, zram: write incompressible pages to backing device)
> so we could regard it as regression because incompressible pages
> doesn't go to backing storage automatically. Instead, usre should
> do it via "echo huge" > /sys/block/zram/writeback" manually.

I'm not in any position to determine the regression risk here.

Why is that feature being removed, anyway?

> If we hear some regression, we could restore the function.

Why not do that now?



  reply index

Thread overview: 23+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-11-27  5:54 [PATCH v3 0/7] zram idle " Minchan Kim
2018-11-27  5:54 ` [PATCH v3 1/7] zram: fix lockdep warning of free block handling Minchan Kim
2018-11-29  2:43   ` Sergey Senozhatsky
2018-11-27  5:54 ` [PATCH v3 2/7] zram: fix double free backing device Minchan Kim
2018-11-29  2:32   ` Sergey Senozhatsky
2018-11-27  5:54 ` [PATCH v3 3/7] zram: refactoring flags and writeback stuff Minchan Kim
2018-11-27  5:54 ` [PATCH v3 4/7] zram: introduce ZRAM_IDLE flag Minchan Kim
2018-11-29  2:29   ` Sergey Senozhatsky
2018-11-27  5:54 ` [PATCH v3 5/7] zram: support idle/huge page writeback Minchan Kim
2018-11-28 23:35   ` Andrew Morton [this message]
2018-11-29  1:36     ` Minchan Kim
2018-11-27  5:54 ` [PATCH v3 6/7] zram: add bd_stat statistics Minchan Kim
2018-11-27  5:54 ` [PATCH v3 7/7] zram: writeback throttle Minchan Kim
2018-11-28 23:41   ` Andrew Morton
2018-11-29  1:55     ` Minchan Kim
2018-11-29  2:23   ` Sergey Senozhatsky
2018-12-02 23:18     ` Minchan Kim
2018-12-03  2:30       ` Sergey Senozhatsky
2018-12-03  2:41         ` Minchan Kim
2018-12-03  2:45           ` Sergey Senozhatsky
2018-11-30  4:36 ` [PATCH v3 0/7] zram idle page writeback Sergey Senozhatsky
2018-12-02 23:20   ` Minchan Kim
2018-12-02 23:28 ` Joey Pabalinas

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