From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:54001) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Z2LF5-0007QX-S3 for qemu-devel@nongnu.org; Tue, 09 Jun 2015 11:15:09 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1Z2LF0-0001T2-RA for qemu-devel@nongnu.org; Tue, 09 Jun 2015 11:15:07 -0400 Received: from e36.co.us.ibm.com ([32.97.110.154]:41161) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Z2LF0-0001Rh-K6 for qemu-devel@nongnu.org; Tue, 09 Jun 2015 11:15:02 -0400 Received: from /spool/local by e36.co.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Tue, 9 Jun 2015 09:15:01 -0600 Received: from b03cxnp08025.gho.boulder.ibm.com (b03cxnp08025.gho.boulder.ibm.com [9.17.130.17]) by d03dlp03.boulder.ibm.com (Postfix) with ESMTP id 5E43219D804A for ; Tue, 9 Jun 2015 09:06:00 -0600 (MDT) Received: from d03av03.boulder.ibm.com (d03av03.boulder.ibm.com [9.17.195.169]) by b03cxnp08025.gho.boulder.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id t59FENvj33882202 for ; Tue, 9 Jun 2015 08:14:23 -0700 Received: from d03av03.boulder.ibm.com (localhost [127.0.0.1]) by d03av03.boulder.ibm.com (8.14.4/8.14.4/NCO v10.0 AVout) with ESMTP id t59FEvch025172 for ; Tue, 9 Jun 2015 09:14:58 -0600 Message-ID: <557702EF.5070003@linux.vnet.ibm.com> Date: Tue, 09 Jun 2015 11:14:55 -0400 From: "Jason J. Herne" MIME-Version: 1.0 References: <1433267209-9882-1-git-send-email-jjherne@linux.vnet.ibm.com> <1433267209-9882-2-git-send-email-jjherne@linux.vnet.ibm.com> <87pp5drzrl.fsf@neno.neno> <556F412C.9090106@linux.vnet.ibm.com> <20150603180356.GE2129@work-vm> <556F4343.6070801@linux.vnet.ibm.com> <5575E7E0.4050209@linux.vnet.ibm.com> <20150609080655.GB2135@work-vm> In-Reply-To: <20150609080655.GB2135@work-vm> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH v2 1/3] cpu: Provide vcpu throttling interface Reply-To: jjherne@linux.vnet.ibm.com List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: "Dr. David Alan Gilbert" Cc: quintela@redhat.com, armbru@redhat.com, qemu-devel@nongnu.org, borntraeger@de.ibm.com, amit.shah@redhat.com, afaerber@suse.de On 06/09/2015 04:06 AM, Dr. David Alan Gilbert wrote: > * Jason J. Herne (jjherne@linux.vnet.ibm.com) wrote: >> On 06/03/2015 02:11 PM, Jason J. Herne wrote: >>> On 06/03/2015 02:03 PM, Dr. David Alan Gilbert wrote: >>>> * Jason J. Herne (jjherne@linux.vnet.ibm.com) wrote: >>>>> On 06/03/2015 03:56 AM, Juan Quintela wrote: >>>>>> "Jason J. Herne" wrote: >>> ... >>>>>> We are checking for throotling on each cpu each 10ms. >>>>>> But on patch 2 we can see that we only change the throotling each >>>>>> time that we call migration_bitmap_sync(), that only happens each round >>>>>> through all the pages. Normally auto-converge only matters for machines >>>>>> with lots of memory, so this is going to happen each more than 10ms (we >>>>>> change it each 4 passes). You changed it to each 2 passes, and you add >>>>>> it a 0.2. I think that I would preffer to just have it each single >>>>>> pass, but add a 0.1 each pass? simpler and end result would be the >>>>>> same? >>>>>> >>>>>> >>>>> >>>>> Well, we certainly could make it run every pass but I think it would get >>>>> a little too aggressive then. The reason is, we do not increment the >>>>> throttle >>>>> rate by adding 0.2 each time. We increment it by multiplying the current >>>>> rate >>>>> by 2. So by doing that every pass we are doubling the exponential growth >>>>> rate. I will admit the numbers I chose are hardly scientific... I >>>>> chose them >>>>> because they seemed to provide a decent balance of "throttling >>>>> aggression" >>>>> in >>>>> my workloads. >>>> >>>> That's the advantage of making them parameters. >>> >>> I see your point. Expecting the user to configure these parameters >>> seems a bit much. But I guess, in theory, it is better to have the >>> ability to change them and not need it, than need it and not have it >>> right? >>> >>> So, as you stated earlier these should hook into MigrationParams >>> somehow? I'll admit this is the first I've seen this construct. If >>> this is the optimal location for the two controls (x-throttle-initial, >>> x-throttle-multiplier?) I can add them there. Will keep defaults of >>> 0.2 for initial and 2.0 for multiplier(is there a better name?)? >>> >> >> So I'm attempting add the initial throttle value and the multiplier to >> MigrationParameters and I've come across a problem. >> hmp_migrate_set_parameter assumes all parameters are ints. Apparently >> floating point is not allowed... >> >> void hmp_migrate_set_parameter(Monitor *mon, const QDict *qdict) >> { >> const char *param = qdict_get_str(qdict, "parameter"); >> int value = qdict_get_int(qdict, "value"); >> >> Also from hmp-commands.hx >> >> { >> .name = "migrate_set_parameter", >> .args_type = "parameter:s,value:i", >> .params = "parameter value", >> .help = "Set the parameter for migration", >> .mhandler.cmd = hmp_migrate_set_parameter, >> .command_completion = migrate_set_parameter_completion, >> }, >> >> I'm hoping someone already has an idea for dealing with this problem? If >> not, I suppose this is a good add-on for Dave's discussion on redesigning >> MigrationParameters. > > Oh, that's yet another problem; hadn't thought about this one. > I don't think the suggestions I had in the previous mail would help that one > either; It might work if you flipped the type to 's' and then parsed > that in the hmp code. > I could change it to a string, and then parse the data on a case-by-case basis in the switch/case logic. I feel like this is making a bad situation worse... But I don't see an easy way around it. -- -- Jason J. Herne (jjherne@linux.vnet.ibm.com)