linux-kernel - Re: [PATCHv3] zram: use notify_free to account all free notifications

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Date:	Tue, 16 Sep 2014 08:03:06 +0900
From:	Minchan Kim <minchan@...nel.org>
To:	Sergey Senozhatsky <sergey.senozhatsky@...il.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Jerome Marchand <jmarchan@...hat.com>,
	Nitin Gupta <ngupta@...are.org>,
	Chao Yu <chao2.yu@...sung.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCHv3] zram: use notify_free to account all free notifications

On Mon, Sep 15, 2014 at 11:49:28PM +0900, Sergey Senozhatsky wrote:
> `notify_free' device attribute accounts the number of slot free notifications
> and internally represents the number of zram_free_page() calls. Slot free
> notifications are sent only when device is used as a swap device, hence
> `notify_free' is used only for swap devices. Since f4659d8e620d08 (zram:
> support REQ_DISCARD) ZRAM handles yet another one free notification (also
> via zram_free_page() call) -- REQ_DISCARD requests, which are sent by a
> filesystem, whenever some data blocks are discarded. However, there is no
> way to know the number of notifications in the latter case.
> 
> Use `notify_free' to account the number of pages freed by zram_bio_discard()
> and zram_slot_free_notify(). Depending on usage scenario `notify_free'
> represents:
>  a) the number of pages freed because of slot free notifications, which is
>    equal to the number of swap_slot_free_notify() calls, so there is no
>    behaviour change
> 
>  b) the number of pages freed because of REQ_DISCARD notifications
> 
> Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@...il.com>
Acked-by: Minchan Kim <minchan@...nel.org>

Thanks a lot!

-- 
Kind regards,
Minchan Kim
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