From: Dave Hansen <dave@linux.vnet.ibm.com>
To: Nitin Gupta <ngupta@vflare.org>
Cc: Seth Jennings <sjenning@linux.vnet.ibm.com>,
linux-mm <linux-mm@kvack.org>,
Dan Magenheimer <dan.magenheimer@oracle.com>,
Robert Jennings <rcj@linux.vnet.ibm.com>,
Brian King <brking@linux.vnet.ibm.com>,
Greg Kroah-Hartman <gregkh@suse.de>
Subject: Re: frontswap/zcache: xvmalloc discussion
Date: Fri, 24 Jun 2011 08:52:44 -0700 [thread overview]
Message-ID: <1308930764.11430.462.camel@nimitz> (raw)
In-Reply-To: <4E042A84.5010204@vflare.org>
On Thu, 2011-06-23 at 23:11 -0700, Nitin Gupta wrote:
> Much of this vpage functionality seems to be already present in mainline
> as "flexible arrays"[1]
That's a good observation. I don't know who wrote that junk, but I bet
they never thought of using it for this purpose. :)
FWIW, for flex_arrays, the biggest limitation is that the objects
currently can not cross page boundaries. The current API also doesn't
have any concept of a release function. We'd need those to do the
unmapping after a get(). It certainly wouldn't be impossible to fix,
but it would probably make it quite a bit more complicated.
The other limitation is that each array can only hold a small number of
megabytes worth of data in each array. We only have a single-level
table lookup, and that first-level table is limited to PAGE_SIZE (minus
a wee bit of metadata).
-- Dave
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next prev parent reply other threads:[~2011-06-24 15:53 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
2011-06-24 6:11 ` Nitin Gupta
2011-06-24 15:52 ` Dave Hansen [this message]
2011-06-25 2:42 ` Nitin Gupta
2011-08-05 16:22 ` Seth Jennings
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