From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751784Ab2DBMwY (ORCPT ); Mon, 2 Apr 2012 08:52:24 -0400 Received: from masquerade.micron.com ([137.201.242.130]:29185 "EHLO masquerade.micron.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751145Ab2DBMwW convert rfc822-to-8bit (ORCPT ); Mon, 2 Apr 2012 08:52:22 -0400 From: "Luca Porzio (lporzio)" To: Hugh Dickins , Arnd Bergmann CC: Rik van Riel , "linaro-kernel@lists.linaro.org" , "linux-mm@kvack.org" , Alex Lemberg , "linux-kernel@vger.kernel.org" , Saugata Das , Venkatraman S , Yejin Moon , Hyojin Jeong , "linux-mmc@vger.kernel.org" , "kernel-team@android.com" Subject: RE: swap on eMMC and other flash Thread-Topic: swap on eMMC and other flash Thread-Index: AQHNDpzybzWjK4z/iEWbFOApOu/42JaDDSoAgAGt6QCAAsVsIA== Date: Mon, 2 Apr 2012 12:52:04 +0000 Message-ID: <26E7A31274623843B0E8CF86148BFE326FB55F8B@NTXAVZMBX04.azit.micron.com> References: <201203301744.16762.arnd@arndb.de> <201203301850.22784.arnd@arndb.de> In-Reply-To: Accept-Language: it-IT, en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-originating-ip: [10.53.32.185] X-TM-AS-Product-Ver: SMEX-10.0.0.4152-6.500.1024-18812.005 X-TM-AS-Result: No--3.406600-0.000000-31 X-TM-AS-User-Approved-Sender: Yes X-TM-AS-User-Blocked-Sender: No x-mt-checkinternalsenderrule: True Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 8BIT MIME-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hugh, Great topics. As per one of Rik original points: > 4) skip writeout of zero-filled pages - this can be a big help > for KVM virtual machines running Windows, since Windows zeroes > out free pages; simply discarding a zero-filled page is not > at all simple in the current VM, where we would have to iterate > over all the ptes to free the swap entry before being able to > free the swap cache page (I am not sure how that locking would > even work) > > with the extra layer of indirection, the locking for this scheme > can be trivial - either the faulting process gets the old page, > or it gets a new one, either way it'll be zero filled > Since it's KVMs realm here, can't KSM simply solve the zero-filled pages problem avoiding unnecessary burden for the Swap subsystem? Cheers, Luca From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Luca Porzio (lporzio)" Subject: RE: swap on eMMC and other flash Date: Mon, 2 Apr 2012 12:52:04 +0000 Message-ID: <26E7A31274623843B0E8CF86148BFE326FB55F8B@NTXAVZMBX04.azit.micron.com> References: <201203301744.16762.arnd@arndb.de> <201203301850.22784.arnd@arndb.de> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable Return-path: In-Reply-To: Content-Language: en-US Sender: owner-linux-mm@kvack.org To: Hugh Dickins , Arnd Bergmann Cc: Rik van Riel , "linaro-kernel@lists.linaro.org" , "linux-mm@kvack.org" , Alex Lemberg , "linux-kernel@vger.kernel.org" , Saugata Das , Venkatraman S , Yejin Moon , Hyojin Jeong , "linux-mmc@vger.kernel.org" , "kernel-team@android.com" List-Id: linux-mmc@vger.kernel.org Hugh, Great topics. As per one of Rik original points: > 4) skip writeout of zero-filled pages - this can be a big help > for KVM virtual machines running Windows, since Windows zeroes > out free pages; simply discarding a zero-filled page is not > at all simple in the current VM, where we would have to iterate > over all the ptes to free the swap entry before being able to > free the swap cache page (I am not sure how that locking would > even work) >=20 > with the extra layer of indirection, the locking for this scheme > can be trivial - either the faulting process gets the old page, > or it gets a new one, either way it'll be zero filled >=20 Since it's KVMs realm here, can't KSM simply solve the zero-filled pages pr= oblem avoiding unnecessary burden for the Swap subsystem? Cheers,=20 Luca -- 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