From: Dan Magenheimer <dan.magenheimer@oracle.com>
To: Seth Jennings <sjenning@linux.vnet.ibm.com>,
Nitin Gupta <ngupta@vflare.org>
Cc: Greg KH <greg@kroah.com>,
gregkh@suse.de, devel@driverdev.osuosl.org,
cascardo@holoscopio.com, linux-kernel@vger.kernel.org,
dave@linux.vnet.ibm.com, linux-mm@kvack.org,
brking@linux.vnet.ibm.com, rcj@linux.vnet.ibm.com
Subject: RE: [PATCH v2 0/3] staging: zcache: xcfmalloc support
Date: Thu, 15 Sep 2011 10:29:51 -0700 (PDT) [thread overview]
Message-ID: <075c4e4c-a22d-47d1-ae98-31839df6e722@default> (raw)
In-Reply-To: <4E72284B.2040907@linux.vnet.ibm.com>
> From: Seth Jennings [mailto:sjenning@linux.vnet.ibm.com]
> Subject: Re: [PATCH v2 0/3] staging: zcache: xcfmalloc support
>
> Hey Nitin,
>
> So this is how I see things...
>
> Right now xvmalloc is broken for zcache's application because
> of its huge fragmentation for half the valid allocation sizes
> (> PAGE_SIZE/2).
Um, I have to disagree here. It is broken for zcache for
SOME set of workloads/data, where the AVERAGE compression
is poor (> PAGE_SIZE/2).
> My xcfmalloc patches are _a_ solution that is ready now. Sure,
> it doesn't so compaction yet, and it has some metadata overhead.
> So it's not "ideal" (if there is such I thing). But it does fix
> the brokenness of xvmalloc for zcache's application.
But at what cost? As Dave Hansen pointed out, we still do
not have a comprehensive worst-case performance analysis for
xcfmalloc. Without that (and without an analysis over a very
large set of workloads), it is difficult to characterize
one as "better" than the other.
> So I see two ways going forward:
>
> 1) We review and integrate xcfmalloc now. Then, when you are
> done with your allocator, we can run them side by side and see
> which is better by numbers. If yours is better, you'll get no
> argument from me and we can replace xcfmalloc with yours.
>
> 2) We can agree on a date (sooner rather than later) by which your
> allocator will be completed. At that time we can compare them and
> integrate the best one by the numbers.
>
> Which would you like to do?
Seth, I am still not clear why it is not possible to support
either allocation algorithm, selectable at runtime. Or even
dynamically... use xvmalloc to store well-compressible pages
and xcfmalloc for poorly-compressible pages. I understand
it might require some additional coding, perhaps even an
ugly hack or two, but it seems possible.
Dan
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next prev parent reply other threads:[~2011-09-15 17:30 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-09-07 14:09 Seth Jennings
2011-09-07 14:09 ` [PATCH v2 1/3] staging: zcache: xcfmalloc memory allocator for zcache Seth Jennings
2011-09-07 14:09 ` [PATCH v2 2/3] staging: zcache: replace xvmalloc with xcfmalloc Seth Jennings
2011-09-07 14:09 ` [PATCH v2 3/3] staging: zcache: add zv_page_count and zv_desc_count Seth Jennings
2011-09-09 20:34 ` [PATCH v2 0/3] staging: zcache: xcfmalloc support Greg KH
2011-09-10 2:41 ` Nitin Gupta
2011-09-12 14:35 ` Seth Jennings
2011-09-13 1:55 ` Nitin Gupta
2011-09-13 15:58 ` Seth Jennings
2011-09-13 21:18 ` Nitin Gupta
2011-09-15 16:31 ` Seth Jennings
2011-09-15 17:29 ` Dan Magenheimer [this message]
2011-09-15 19:24 ` Seth Jennings
2011-09-15 20:07 ` Dan Magenheimer
2011-10-03 15:59 ` Dave Hansen
2011-10-03 17:54 ` Nitin Gupta
2011-10-03 18:22 ` Dave Hansen
2011-10-05 1:03 ` Dan Magenheimer
2011-09-15 22:17 ` Dave Hansen
2011-09-15 22:27 ` Dan Magenheimer
2011-09-16 17:36 ` Nitin Gupta
2011-09-16 17:52 ` Nitin Gupta
2011-09-16 17:46 ` Nitin Gupta
2011-09-16 18:33 ` Seth Jennings
2011-11-01 17:30 ` Dave Hansen
2011-11-01 18:35 ` Dan Magenheimer
2011-11-02 2:42 ` Nitin Gupta
2011-09-29 17:47 ` Seth Jennings
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