Re: [PATCH v4 0/3] zram/zsmalloc promotion

[Minchan Kim <minchan@kernel.org>]

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Hi Andrew,

On Wed, Nov 7, 2012 at 8:32 AM, Andrew Morton <akpm@linux-foundation.org>
wrote:
> On Fri, 2 Nov 2012 16:12:44 +0900
> Minchan Kim <minchan@kernel.org> wrote:
>
>> This patchset promotes zram/zsmalloc from staging.
>
> The changelogs are distressingly short of *reasons* for doing this!
>
>> Both are very clean and zram have been used by many embedded product
>> for a long time.
>
> Well that's interesting.
>
> Which embedded products? How are they using zram and what benefit are
> they observing from it, in what scenarios?
>

At least, major TV companys have used zram as swap since two years ago and
recently our production team released android smart phone with zram which
is used as swap, too.
And there is trial to use zram as swap in ChromeOS project, too. (Although
they report some problem recently, it was not a problem of zram).
When you google zram, you can find various usecase in xda-developers.

With my experience, the benefit in real practice was to remove jitter of
video application. It would be effect of efficient memory usage by
compression but more issue is whether swap is there or not in the system.
As you know, recent mobile platform have used JAVA so there are lots of
anonymous pages. But embedded system normally doesn't use eMMC or SDCard as
swap because there is wear-leveling issue and latency so we can't reclaim
anymous pages. It sometime ends up making system very slow when it requires
to get contiguous memory and even many file-backed pages are evicted. It's
never what embedded people want it. Zram is one of best solution for that.

It's very hard to type with mobile phone. :(

-- 
Kind regards,
Minchan Kim

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