From: Dan Magenheimer <dan.magenheimer@oracle.com>
To: Seth Jennings <sjenning@linux.vnet.ibm.com>
Cc: linux-mm <linux-mm@kvack.org>, Nitin Gupta <ngupta@vflare.org>,
Robert Jennings <rcj@linux.vnet.ibm.com>,
Brian King <brking@linux.vnet.ibm.com>,
Greg Kroah-Hartman <gregkh@suse.de>, Dave Hansen <dave@sr71.net>
Subject: RE: frontswap/zcache: xvmalloc discussion
Date: Thu, 30 Jun 2011 09:09:37 -0700 (PDT) [thread overview]
Message-ID: <f5f6fc78-5d54-4ea7-abbb-9c0cb14391dc@default> (raw)
In-Reply-To: <f6415652-5925-4aad-b8be-900ce3afd902@default>
> FWIW, I've measured the distribution of zsize (pages compressed
> with frontswap) on my favorite workload (kernel "make -j2" on
> mem=512M to force lots of swapping) and the mean is small, close
> to 1K (PAGE_SIZE/4). I've added some sysfs shows for both
> the current and cumulative distribution (0-63 bytes, 64-127
> bytes, ..., 4032-4095 bytes) for the next update.
>
> I tried your program on the text of Moby Dick and the mean
> was still under 1500 bytes ((3*PAGE_SIZE)/8) with a good
> broad distribution for zsize.
Oops, on retry this morning, I am now clearly seeing the poor
compression. Not sure what is different from last night,
but I suspect I was "watch"ing the new sysfs output during
massive swapping during the run of the test program and
it wasn't updated until program completion (at which point
I was no longer perusing the sysfs output).
Sorry for the noise. However, now that I have a test case
I am implementing another sysfs tunable to reject poorly-
compressible pages that would drive the mean zsize
above the tunable. Zcache will reject these pages until
the mean falls below the threshold. (Setting it to
PAGE_SIZE will continue current behavior, but I've set
the default to (5*PAGE_SIZE)/8 for now.)
Dan
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next prev parent reply other threads:[~2011-06-30 16:10 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-06-22 19:15 frontswap/zcache: xvmalloc discussion Seth Jennings
2011-06-22 19:23 ` [PATCH] Add zv_pool_pages_count to zcache sysfs Seth Jennings
2011-06-23 15:38 ` Dave Hansen
2011-06-23 16:38 ` frontswap/zcache: xvmalloc discussion Dan Magenheimer
2011-06-23 21:59 ` Seth Jennings
2011-06-24 22:40 ` Dan Magenheimer
2011-06-30 2:31 ` Dan Magenheimer
2011-06-30 16:09 ` Dan Magenheimer [this message]
2011-06-24 6:11 ` Nitin Gupta
2011-06-24 15:52 ` Dave Hansen
2011-06-25 2:42 ` Nitin Gupta
2011-08-05 16:22 ` Seth Jennings
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