linux-kernel - Re: [PATCH] mm: extend zero pages to same element pages for zram

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Date:   Fri, 13 Jan 2017 15:36:14 +0900
From:   Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>
To:     Minchan Kim <minchan@...nel.org>
Cc:     Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>,
        zhouxianrong@...wei.com, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, akpm@...ux-foundation.org,
        sergey.senozhatsky@...il.com, ngupta@...are.org,
        Mi.Sophia.Wang@...wei.com, zhouxiyu@...wei.com,
        weidu.du@...wei.com, zhangshiming5@...wei.com,
        won.ho.park@...wei.com
Subject: Re: [PATCH] mm: extend zero pages to same element pages for zram

On (01/13/17 15:23), Minchan Kim wrote:
[..]
> > > Please add same_pages to tail of the stat
> > 
> > sounds ok to me. and yes, can deprecate zero_pages.
> > 
> > seems that with that patch the concept of ZRAM_ZERO disappears. both
> > ZERO and SAME_ELEMENT pages are considered to be the same thing now.
> 
> Right.
> 
> > which is fine and makes sense to me, I think. and if ->.same_pages will
> > replace ->.zero_pages in mm_stat() then I'm also OK. yes, we will see
> > increased number in the last column of mm_stat file, but I don't tend
> > to see any issues here. Minchan, what do you think?
> 
> Could you elaborate a bit? Do you mean this?
> 
>         ret = scnprintf(buf, PAGE_SIZE,
>                         "%8llu %8llu %8llu %8lu %8ld %8llu %8lu\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.zero_pages),
>                         (u64)atomic64_read(&zram->stats.same_pages),
>                         pool_stats.pages_compacted);

yes, correct.

do we need to export it as two different stats (zero_pages and
same_pages), if those are basically same thing internally?

	-ss