From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-yh0-f46.google.com (mail-yh0-f46.google.com [209.85.213.46]) by kanga.kvack.org (Postfix) with ESMTP id 873336B0038 for ; Fri, 26 Jun 2015 04:56:36 -0400 (EDT) Received: by yhnv31 with SMTP id v31so40444706yhn.1 for ; Fri, 26 Jun 2015 01:56:36 -0700 (PDT) Received: from SMTP.CITRIX.COM (smtp.citrix.com. [66.165.176.89]) by mx.google.com with ESMTPS id b185si12668287ywd.207.2015.06.26.01.56.35 for (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Fri, 26 Jun 2015 01:56:35 -0700 (PDT) Message-ID: <558D13BF.9030907@citrix.com> Date: Fri, 26 Jun 2015 09:56:31 +0100 From: David Vrabel MIME-Version: 1.0 Subject: Re: [Xen-devel] [PATCHv1 6/8] xen/balloon: only hotplug additional memory if required References: <1435252263-31952-1-git-send-email-david.vrabel@citrix.com> <1435252263-31952-7-git-send-email-david.vrabel@citrix.com> <20150625211834.GO14050@olila.local.net-space.pl> In-Reply-To: <20150625211834.GO14050@olila.local.net-space.pl> Content-Type: text/plain; charset="windows-1252" Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Daniel Kiper , David Vrabel Cc: linux-mm@kvack.org, xen-devel@lists.xenproject.org, Boris Ostrovsky , linux-kernel@vger.kernel.org On 25/06/15 22:18, Daniel Kiper wrote: > On Thu, Jun 25, 2015 at 06:11:01PM +0100, David Vrabel wrote: >> Now that we track the total number of pages (included hotplugged >> regions), it is easy to determine if more memory needs to be >> hotplugged. >> >> Signed-off-by: David Vrabel >> --- >> drivers/xen/balloon.c | 16 +++++++++++++--- >> 1 file changed, 13 insertions(+), 3 deletions(-) >> >> diff --git a/drivers/xen/balloon.c b/drivers/xen/balloon.c >> index 960ac79..dd41da8 100644 >> --- a/drivers/xen/balloon.c >> +++ b/drivers/xen/balloon.c >> @@ -241,12 +241,22 @@ static void release_memory_resource(struct resource *resource) >> * bit set). Real size of added memory is established at page onlining stage. >> */ >> >> -static enum bp_state reserve_additional_memory(long credit) >> +static enum bp_state reserve_additional_memory(void) >> { >> + long credit; >> struct resource *resource; >> int nid, rc; >> unsigned long balloon_hotplug; >> >> + credit = balloon_stats.target_pages - balloon_stats.total_pages; >> + >> + /* >> + * Already hotplugged enough pages? Wait for them to be >> + * onlined. >> + */ > > Comment is wrong or at least misleading. Both values does not depend on onlining. If we get here and credit <=0 then the balloon is empty and we have already hotplugged enough sections to reach target. We need to wait for userspace to online the sections that already exist. >> + if (credit <= 0) >> + return BP_EAGAIN; > > Not BP_EAGAIN for sure. It should be BP_DONE but then balloon_process() will go > into loop until memory is onlined at least up to balloon_stats.target_pages. > BP_ECANCELED does work but it is misleading because it is not an error. So, maybe > we should introduce BP_STOP (or something like that) which works like BP_ECANCELED > and is not BP_ECANCELED. We don't want to spin while waiting for userspace to online a new section so BP_EAGAIN is correct here as it causes the balloon process to be rescheduled at a later time. David -- 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/ . Don't email: email@kvack.org