From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ingo Molnar Date: Tue, 24 Jan 2006 09:02:35 +0000 Subject: Re: [PATCH] SN2 user-MMIO CPU migration Message-Id: <20060124090235.GA673@elte.hu> List-Id: References: <20060118163305.Y42462@chenjesu.americas.sgi.com> In-Reply-To: <20060118163305.Y42462@chenjesu.americas.sgi.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: linux-ia64@vger.kernel.org * Brent Casavant wrote: > I agree with him that it's not wonderful to hook into mainline > scheduler code to solve this, but the alternative is what I presented > here: check if old CPU = new CPU at each context switch-in, entirely > within IA64 code. what's the problem with doing that? It's a single comparison [of two values we already have accessed in that function!] and a rarely taken branch in a single subarch of a single arch's switch_to() function. If this use (of migration related arch functionality) becomes more widespread then we can generalize it, but right now i just dont see the point, given that the two solutions are almost totally equivalent in terms of "overhead". Ingo