From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jeremy Fitzhardinge Subject: Re: [02/17][PATCH] Implement smp_call_function_mask for ia64 - V8 Date: Tue, 01 Apr 2008 09:06:03 -0700 Message-ID: <47F25D6B.40704@goop.org> References: <42DFA526FC41B1429CE7279EF83C6BDC01048240@pdsmsx415.ccr.corp.intel.com> <47F0AB18.2010707@sgi.com> <47F0FCFE.5010106@goop.org> <47F1F3B1.7020308@sgi.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: Jeremy Fitzhardinge , Carsten Otte , "Luck, Tony" , linux-ia64@vger.kernel.org, kvm-ia64-devel@lists.sourceforge.net, kvm-devel@lists.sourceforge.net, virtualization@lists.linux-foundation.org, "Xu, Anthony" , "Zhang, Xiantao" To: Jes Sorensen Return-path: In-Reply-To: <47F1F3B1.7020308@sgi.com> Sender: linux-ia64-owner@vger.kernel.org List-Id: kvm.vger.kernel.org Jes Sorensen wrote: > Jeremy Fitzhardinge wrote: > >> Jes Sorensen wrote: >> This change has been on the x86 side for ages, and not even Ingo made a >> peep about it ;) >> > > Mmmm, last time I looked, x86 didn't scale to any interesting number > of CPUs :-) > Well, I guess you need all those CPUs if scanning a 64-word bitvector takes anything like the time it takes to do an IPI... > I wasn't suggesting we shouldn't have both interfaces, merely > questioning why adding what to me seems like an unnecessary performance > hit for the classic case of the call. I don't mind how many interfaces there are, so long as there only needs to be one place to hook to plug in the Xen version of smp_call_function_whatever. Perhaps the answer is to just hook the IPI mechanism itself rather than the whole of smp_call_function_mask... Have you looked at Jens Axboe's patches to make all this stuff a lot more arch-common? J