Re: [PATCH V2 2/3] drivers/staging: zcache: host services and PAM services

From: Minchan Kim
Date: Wed Feb 09 2011 - 18:57:42 EST


On Thu, Feb 10, 2011 at 1:39 AM, Dan Magenheimer
<dan.magenheimer@xxxxxxxxxx> wrote:
>
>
>> From: Minchan Kim [mailto:minchan.kim@xxxxxxxxx]
>
>> As I read your comment, I can't find the benefit of zram compared to
>> frontswap.
>
> Well, I am biased, but I agree that frontswap is a better technical
> solution than zram. ;-) ÂBut "dynamic-ity" is very important to
> me and may be less important to others.
>
> I thought of these other differences, both technical and
> non-technical:
>
> - Zram is minimally invasive to the swap subsystem, requiring only
> Âone hook which is already upstream (though see below) and is
> Âapparently already used by some Linux users. ÂFrontswap is somewhat

Yes. I think what someone is using it is a problem.

> Âmore invasive and, UNTIL zcache-was-kztmem was posted a few weeks
> Âago, had no non-Xen users (though some distros are already shipping
> Âthe hooks in their kernels because Xen supports it); as a result,
> Âfrontswap has gotten almost no review by kernel swap subsystem
> Âexperts who I'm guessing weren't interested in anything that
> Ârequired Xen to use... hopefully that barrier is now resolved
> Â(but bottom line is frontswap is not yet upstream).

That's why I suggested to remove frontswap in this turn.
If any swap experts has a interest, maybe you can't receive any ack or
review about the part in this series. Maybe maintainers ends up
hesitating the merge.

If zcache except frontswap is merged into mainline or receive enough
review, then you can try merging frontswap as further step.

Thanks.

--
Kind regards,
Minchan Kim
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