linux-kernel - Re: [PATCH] mm/zsmalloc: add compact column to pool stat

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Date:	Mon, 29 Feb 2016 15:26:28 +0900
From:	Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>
To:	Minchan Kim <minchan@...nel.org>
Cc:	Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
	Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org,
	Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>
Subject: Re: [PATCH] mm/zsmalloc: add compact column to pool stat

Hello,

On (02/29/16 15:02), Minchan Kim wrote:
> On Sat, Feb 27, 2016 at 03:23:53PM +0900, Sergey Senozhatsky wrote:
> > Add a new column to pool stats, which will tell us class' zs_can_compact()
> > number, so it will be easier to analyze zsmalloc fragmentation.
> 
> Just nitpick:
> 
> Strictly speaking, zs_can_compact number is number of "ideal freeable page
> by compaction". How about using high level term in description rather than
> function name?

OK, makes sense.


> > At the moment, we have only numbers of FULL and ALMOST_EMPTY classes, but
> > they don't tell us how badly the class is fragmented internally.
> > 
> > The new /sys/kernel/debug/zsmalloc/zramX/classes output look as follows:
> > 
> >  class  size almost_full almost_empty obj_allocated   obj_used pages_used pages_per_zspage compact
> > [..]
> >     12   224           0            2           146          5          8                4       4
> >     13   240           0            0             0          0          0                1       0
> >     14   256           1           13          1840       1672        115                1      10
> >     15   272           0            0             0          0          0                1       0
> > [..]
> >     49   816           0            3           745        735        149                1       2
> >     51   848           3            4           361        306         76                4       8
> >     52   864          12           14           378        268         81                3      21
> >     54   896           1           12           117         57         26                2      12
> >     57   944           0            0             0          0          0                3       0
> > [..]
> >  Total                26          131         12709      10994       1071                      134
> > 
> > For example, from this particular output we can easily conclude that class-896
> > is heavily fragmented -- it occupies 26 pages, 12 can be freed by compaction.
> 
> How about using "freeable" or something which could represent "freeable"?
> IMO, it's more strightforward for user.

OK. didn't want to put any long column name there, which would bloat the
output. will take a look.

> Other than that,
> 
> Acked-by: Minchan Kim <minchan@...nel.org>
> 
> 
> Thanks for the nice job!

thanks.

	-ss