linux-kernel - Re: [PATCH v4 2/4] zram: implement deduplication in zram

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Date:   Wed, 26 Apr 2017 14:57:03 +0900
From:   Joonsoo Kim <js1304@...il.com>
To:     Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Minchan Kim <minchan@...nel.org>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        linux-kernel@...r.kernel.org, kernel-team@....com
Subject: Re: [PATCH v4 2/4] zram: implement deduplication in zram

On Wed, Apr 26, 2017 at 11:14:52AM +0900, Sergey Senozhatsky wrote:
> Hello,
> 
> On (04/26/17 09:52), js1304@...il.com wrote:
> [..]
> >  	ret = scnprintf(buf, PAGE_SIZE,
> > -			"%8llu %8llu %8llu %8lu %8ld %8llu %8lu\n",
> > +			"%8llu %8llu %8llu %8lu %8ld %8llu %8lu %8llu %8llu\n",
> >  			orig_size << PAGE_SHIFT,
> >  			(u64)atomic64_read(&zram->stats.compr_data_size),
> >  			mem_used << PAGE_SHIFT,
> >  			zram->limit_pages << PAGE_SHIFT,
> >  			max_used << PAGE_SHIFT,
> >  			(u64)atomic64_read(&zram->stats.same_pages),
> > -			pool_stats.pages_compacted);
> > +			pool_stats.pages_compacted,
> > +			zram_dedup_dup_size(zram),
> > +			zram_dedup_meta_size(zram));
> 
> hm... should't we subtract zram_dedup_dup_size(zram) from
> ->stats.compr_data_size? we don't use extra memory for dedupped
> pages. or don't inc ->stats.compr_data_size for dedupped pages?

Hmm... My intention is to keep previous stat as much as possible. User
can just notice the saving by only checking mem_used.

However, it's also odd that compr_data_size doesn't show actual
compressed data size.

Minchan, what do you think about it?

Thanks.