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

From: Minchan Kim
Date: Fri Jan 13 2017 - 03:08:01 EST


On Fri, Jan 13, 2017 at 04:02:45PM +0900, Sergey Senozhatsky wrote:
> On (01/13/17 15:47), Minchan Kim wrote:
> [..]
> > > > 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?
> >
> > So, let summary up.
> >
> > 1. replace zero_page stat into same page stat in mm_stat
> > 2. s/zero_pages/same_pages/Documentation/blockdev/zram.txt
> > 3. No need to warn to "cat /sys/block/zram0/mm_stat" user to see zero_pages
> > about semantic change
>
> 1) account zero_page and same_pages in one attr.
>
> this already is in the patch.
>
> 2) do not rename zero_pages attr.
>
> we can't do this so fast, I think.
>
>
> > 3. No need to warn to "cat /sys/block/zram0/mm_stat" user to see zero_pages
> > about semantic change
>
> yes. we just _may_ have more pages (depending on data pattern) which we treat
> as "zero" pages internally. this results in lower memory consumption. I don't
> think warn users about this change is necessary; they won't be able to do
> anything about it anyway. zero_pages stat is pretty much just a fun number to
> know. isn't it?
>

I just wanted to confirm your thought.
I hope anyone doesn't is sensitive on that number. ;)
Let's replace zero_page stat field in mm_stat.

Thanks.