From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([208.118.235.92]:47538) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1SuQc5-0001jC-SO for qemu-devel@nongnu.org; Thu, 26 Jul 2012 12:08:34 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1SuQbw-0000hu-C0 for qemu-devel@nongnu.org; Thu, 26 Jul 2012 12:08:33 -0400 Received: from mx1.redhat.com ([209.132.183.28]:48446) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1SuQbw-0000ho-2Y for qemu-devel@nongnu.org; Thu, 26 Jul 2012 12:08:24 -0400 Message-ID: <50116B73.2070401@redhat.com> Date: Thu, 26 Jul 2012 19:08:19 +0300 From: Avi Kivity MIME-Version: 1.0 References: <1342803890-1795-1-git-send-email-ehabkost@redhat.com> <1342803890-1795-3-git-send-email-ehabkost@redhat.com> <20120723122014.GB26120@redhat.com> <20120725184220.GI13029@otherpad.lan.raisama.net> <20120726060840.GQ26120@redhat.com> <20120726141653.GD27859@shell.eng.rdu.redhat.com> <50115A4D.2050303@redhat.com> <20120726150701.GD7834@shell.eng.rdu.redhat.com> In-Reply-To: <20120726150701.GD7834@shell.eng.rdu.redhat.com> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [SeaBIOS PATCH 2/2] allow CPUs to have non-contiguous Local APIC IDs (v2) List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Eduardo Habkost Cc: Igor Mammedov , Kevin O'Connor , seabios@seabios.org, qemu-devel@nongnu.org, Gleb Natapov On 07/26/2012 06:07 PM, Eduardo Habkost wrote: > On Thu, Jul 26, 2012 at 05:55:09PM +0300, Avi Kivity wrote: >> On 07/26/2012 05:16 PM, Eduardo Habkost wrote: >> >> > >> >> > It's possible to replace the atomic read of CountCPUs with the bitmap weight >> >> > calculation on the loop, but: is it really worth it? >> >> > >> >> Why not? This eliminates one more global state. >> > >> > Maybe we can simply make it stop being global and be used only by the >> > smp.c initialization code? >> > >> > Even if the variable didn't exist yet, I think I would add it myself: >> > it's simpler and more efficient to calculate the bitmap weight once, >> > while filling the bitmap, than recalculating it every time on the >> > while(cmos_smp_count) loop. >> >> So you're spinning more efficiently? > > No, coding more efficiently. I'm lazy. :-) > > I don't want to risk breaking that part of the code to save 2 bytes of > memory. It's possible to impement it reliably, yes, but it's also very > easy to introduce a subtle bug, so why touch something that works > perfectly just to save 2 bytes? Like gleb, I prefer avoiding derived state which can get out-of-sync. -- error compiling committee.c: too many arguments to function