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From: Minchan Kim <minchan@kernel.org>
To: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
	Nitin Gupta <ngupta@vflare.org>,
	linux-kernel@vger.kernel.org,
	Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
Subject: Re: [PATCH 0/6] new zram statistics reporting scheme
Date: Thu, 12 Mar 2015 10:55:58 +0900	[thread overview]
Message-ID: <20150312015558.GG10820@blaptop> (raw)
In-Reply-To: <1426000114-4471-1-git-send-email-sergey.senozhatsky@gmail.com>

Hi Sergey,

On Wed, Mar 11, 2015 at 12:08:28AM +0900, Sergey Senozhatsky wrote:
> Hello,
> 
> This patch introduces rework to zram stats. We have per-stat sysfs
> nodes, and it makes things a bit hard to use in user space: it doesn't
> give an immediate stats 'snapshot', it requires user space to use
> more syscals -- open, read, close for every stat file, with 
> appropriate error checks on every step, etc.
> 
> First, zram now accounts block layer statistics. available in
> /sys/block/zram<id>/stat and /proc/diskstats files. So some new
> stats are available (see Documentation/block/stat.txt), besides,
> zram's activities are now can be monitored by sysstat's iostat
> or similar tools.
> 
> Example:
> cat /sys/block/zram0/stat
> 248     0    1984    0   251029     0  2008232   5120   0   5116   5116
> 
> 
> 
> Second, group currently exported on per-stat basis nodes into two
> categories (files):
> 
> -- zram<id>/io_stat
> accumulates device's IO stats, that are not accounted by block layer,
> and contains:
>         failed_reads
>         failed_writes
>         invalid_io
>         notify_free
> 
> Example:
> cat /sys/block/zram0/io_stat
> 0        0        0   652572
> 
> 
> -- zram<id>/mm_stat
> accumulates zram mm stats and contains:
>         orig_data_size
>         compr_data_size
>         mem_used_total
>         mem_limit
>         mem_used_max
>         zero_pages
>         num_migrated
> 
> Example:
> cat /sys/block/zram0/mm_stat
> 434634752 270288572 279158784        0 579895296    15060        0
> 
> 
> per-stat sysfs nodes are now considered to be deprecated and we plan
> to remove them (and clean up some of the existing stat code) in two
> years (as of now, there is no warning printed to syslog about deprecated
> stats being used). user space is advised to use the above mentioned 3
> files.
> 
> 
> note:
> util-linux mailing list is not Cc-ed into this series. once we settle
> it down, I'll write to Karel. (we have several months ahead until 4.1
> will be released).

I really appreciate you enhance stat functions, esp, working with iostat!

One thing I want to discuss is sometime we could remove RO fields
in /sys/block/zram/ but we couldn't remove RW fields because
io_stat/mm_stat doesn't have any writable option now so users will
have two options to read stat. For exmaple,

        cat /sys/block/zram/mem_used_max
        cat /sys/block/zram/mm_stat | awk friend

How about changing only writeable, not readable for duplicated stats
in /sys/block/zram? So, user will have writeable stat to set some
options in /sys/block/zram and readable stat to get some data in
/sys/block/zram/[io|mm]_stat if the stat is duplicated in both.


-- 
Kind regards,
Minchan Kim

  parent reply	other threads:[~2015-03-12  1:56 UTC|newest]

Thread overview: 21+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-03-10 15:08 Sergey Senozhatsky
2015-03-10 15:08 ` [PATCH 1/6] zram: remove `num_migrated' device attr Sergey Senozhatsky
2015-03-12  1:16   ` Minchan Kim
2015-03-12  1:22     ` Sergey Senozhatsky
2015-03-10 15:08 ` [PATCH 2/6] zram: move compact_store() to sysfs functions area Sergey Senozhatsky
2015-03-12  1:24   ` Minchan Kim
2015-03-10 15:08 ` [PATCH 3/6] zram: use generic start/end io accounting Sergey Senozhatsky
2015-03-12  1:25   ` Minchan Kim
2015-03-10 15:08 ` [PATCH 4/6] zram: describe device attrs in documentation Sergey Senozhatsky
2015-03-12  1:33   ` Minchan Kim
2015-03-12  1:47     ` Sergey Senozhatsky
2015-03-10 15:08 ` [PATCH 5/6] zram: export new 'io_stat' sysfs attrs Sergey Senozhatsky
2015-03-12  1:36   ` Minchan Kim
2015-03-10 15:08 ` [PATCH 6/6] zram: export new 'mm_stat' " Sergey Senozhatsky
2015-03-12  1:41   ` Minchan Kim
2015-03-12  1:54     ` Sergey Senozhatsky
2015-03-12  1:55 ` Minchan Kim [this message]
2015-03-12  2:16   ` [PATCH 0/6] new zram statistics reporting scheme Sergey Senozhatsky
2015-03-12  5:03     ` Sergey Senozhatsky
2015-03-12  5:11     ` Minchan Kim
2015-03-12  5:24       ` Sergey Senozhatsky

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