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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 7/7] zram: writeback throttle
Date: Wed, 28 Nov 2018 15:41:41 -0800
Message-ID: <20181128154141.d67b70957bc4833d9f0d6635@linux-foundation.org> (raw)
In-Reply-To: <20181127055429.251614-8-minchan@kernel.org>

On Tue, 27 Nov 2018 14:54:29 +0900 Minchan Kim <minchan@kernel.org> wrote:

> On small memory system, there are lots of write IO so if we use
> flash device as swap, there would be serious flash wearout.
> To overcome the problem, system developers need to design write
> limitation strategy to guarantee flash health for entire product life.
> 
> This patch creates a new konb "writeback_limit" on zram. With that,
> if current writeback IO count(/sys/block/zramX/io_stat) excceds
> the limitation, zram stops further writeback until admin can reset
> the limit.

I'm not really understanding this.  Does this only refer to suspending
the idle page writeback feature?  Not all zram writeback, surely?

I don't think the documentation gives an administrator sufficient
information to effectively use the feature.  Some additional discussion
would help.  What sort of values should it be set to and why?

And what is the default setting?  And why?

And the limit isn't persistent across reboots which makes me wonder
whether the overall feature is particularly valuable?


  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 page writeback 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
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 [this message]
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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