linux-kernel - Re: [PATCH 3/3] zram: rework reported to end-user zram statistics

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Date:	Tue, 14 Jan 2014 16:53:55 +0300
From:	Sergey Senozhatsky <sergey.senozhatsky@...il.com>
To:	Jerome Marchand <jmarchan@...hat.com>
Cc:	Minchan Kim <minchan@...nel.org>, Nitin Gupta <ngupta@...are.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/3] zram: rework reported to end-user zram statistics

On (01/14/14 14:43), Jerome Marchand wrote:
[..]
> >>
> >> That's weird: good/bad_compress are accounted, but it seems to me that
> >> they are to never used in any way. If so, there is indeed no reason to
> >> keep them.
> >>
> >>
> >>> Account each sub-request
> >>> compression size so we can calculate real device compression ratio.
> >>
> >> Your patch doesn't change the way pages_stored and compr[essed]_size
> >> are accounted. What does your patch change that allow us to calculate
> >> the "real" compression ratio?
> >>
> >>>
> >>> 4) reported zram stats:
> >>>   - num_writes  -- number of writes
> >>>   - num_reads  -- number of reads
> >>>   - pages_stored -- number of pages currently stored
> >>>   - compressed_size -- compressed size of pages stored
> >>
> >> Wouldn't it be more practical to report the original and compressed
> >> data sizes using the same units as it is currently done?
> >>
> > 
> > hm, do we really need pages_stored stats? what kind of unseful information it
> > shows to end user?.. perhaps, it's better to replace it with accounted passed
> > bvec->bv_len (as uncompressed_size).
> > 
> 
> That's really going to complicates things. We would need to keep track
> of which sectors of a particular page has been written to. It's much
> easier to keep current page granularity and consider any partial I/O
> as an whole page I/O.
> 

fair enough. thank you.

2/3 and 3/3 were changed according to your comments:
- 2/3 drop READA check
- 3/3 update commit message.

ready to re-publish. may I add your ACK to all 3 patches or just to 1/3?

	-ss

> > 
> >> Jerome
> >>
> >>>   - pages_zero  -- number of zero filled pages
> >>>   - failed_read -- number of failed reads
> >>>   - failed_writes -- can happen when memory is too low
> >>>   - invalid_io   -- non-page-aligned I/O requests
> >>>   - notify_free  -- number of swap slot free notifications
> >>>   - memory_used -- zs pool zs_get_total_size_bytes()
> >>>
> >>> Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@...il.com>
> 
> 
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