From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail203.messagelabs.com (mail203.messagelabs.com [216.82.254.243]) by kanga.kvack.org (Postfix) with ESMTP id C05AD90023D for ; Fri, 24 Jun 2011 11:53:00 -0400 (EDT) Received: from d01relay06.pok.ibm.com (d01relay06.pok.ibm.com [9.56.227.116]) by e4.ny.us.ibm.com (8.14.4/8.13.1) with ESMTP id p5OFVCdR021044 for ; Fri, 24 Jun 2011 11:31:12 -0400 Received: from d01av04.pok.ibm.com (d01av04.pok.ibm.com [9.56.224.64]) by d01relay06.pok.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id p5OFqtnK893080 for ; Fri, 24 Jun 2011 11:52:55 -0400 Received: from d01av04.pok.ibm.com (loopback [127.0.0.1]) by d01av04.pok.ibm.com (8.14.4/8.13.1/NCO v10.0 AVout) with ESMTP id p5OFqtqr032247 for ; Fri, 24 Jun 2011 11:52:55 -0400 Subject: Re: frontswap/zcache: xvmalloc discussion From: Dave Hansen In-Reply-To: <4E042A84.5010204@vflare.org> References: <4E023F61.8080904@linux.vnet.ibm.com> <4E042A84.5010204@vflare.org> Content-Type: text/plain; charset="UTF-8" Date: Fri, 24 Jun 2011 08:52:44 -0700 Message-ID: <1308930764.11430.462.camel@nimitz> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Nitin Gupta Cc: Seth Jennings , linux-mm , Dan Magenheimer , Robert Jennings , Brian King , Greg Kroah-Hartman 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 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org