linux-kernel - Re: + zram-support-compaction.patch added to -mm tree

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Message-ID: <20150309005718.GA794@swordfish>
Date:	Mon, 9 Mar 2015 09:57:18 +0900
From:	Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>
To:	Minchan Kim <minchan@...nel.org>
Cc:	Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>,
	akpm@...ux-foundation.org, ddstreet@...e.org, gunho.lee@....com,
	iamjoonsoo.kim@....com, jmarchan@...hat.com, juno.choi@....com,
	mel@....ul.ie, ngupta@...are.org, semenzato@...gle.com,
	sergey.senozhatsky@...il.com, sjennings@...iantweb.net,
	mm-commits@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: + zram-support-compaction.patch added to -mm tree

On (03/09/15 09:49), Minchan Kim wrote:
> > rather a discussion question.
> > 
> > Minchan, do you want to provide num_migrated as part of zsmalloc stats rather
> > than having yet another zram attr? we already provide zsmalloc stats and this
> > type of information seems to belong there. just idea.
> 
> Hmm, CONFIG_ZSMALLOC_STAT is actually to show zsmalloc internals.

well, to be fair, compaction is a zsmalloc internal. zram has nothing to do with
it.

but do we we even need this stat? it seems that

   mem_total_used (before compaction) - mem_total_user (after comapction)

will give user an idea on how much memory was compacted.

	-ss

> That's why it is on debugfs. If we add the stat into zsmalloc, we should turn on debugfs
> and CONFIG_ZSMALLOC_STAT to see *a* stat. Even, CONFIG_ZSMALLOC_STAT will add
> unncessary overheads to account another stats fo zsmalloc internals.
> 
> As well, if we add auto-compacion like stuff in zsmalloc(ie, it will trigger
> by itself if fragmention is over to predefined theshold), the stat will
> accumulate stat while someone want to see snapshot compaction effiecieny
> of the moment.
> 
> So, I want to keep it in zram now.
> 
> -- 
> Kind regards,
> Minchan Kim
> 
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