From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from ozlabs.org (bilbo.ozlabs.org [103.22.144.67]) (using TLSv1.2 with cipher ADH-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 3xbZXs6CqHzDqTt for ; Mon, 21 Aug 2017 23:39:09 +1000 (AEST) In-Reply-To: <20170727062455.15404-2-aneesh.kumar@linux.vnet.ibm.com> To: "Aneesh Kumar K.V" , benh@kernel.crashing.org, paulus@samba.org From: Michael Ellerman Cc: linuxppc-dev@lists.ozlabs.org, "Aneesh Kumar K.V" Subject: Re: [v3,2/3] powerpc/mm: Don't send IPI to all cpus on THP updates Message-Id: <3xbZXs5CkYz9sDB@ozlabs.org> Date: Mon, 21 Aug 2017 23:39:09 +1000 (AEST) List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Thu, 2017-07-27 at 06:24:54 UTC, "Aneesh Kumar K.V" wrote: > Now that we made sure that lockless walk of linux page table is mostly limitted > to current task(current->mm->pgdir) we can update the THP update sequence to > only send IPI to cpus on which this task has run. This helps in reducing the IPI > overload on systems with large number of CPUs. > > W.r.t kvm even though kvm is walking page table with vpc->arch.pgdir, it is > done only on secondary cpus and in that case we have primary cpu added to > task's mm cpumask. Sending an IPI to primary will force the secondary to do > a vm exit and hence this mm cpumask usage is safe here. > > W.r.t CAPI, we still end up walking linux page table with capi context MM. For > now the pte lookup serialization sends an IPI to all cpus in CPI is in use. We > can further improve this by adding the CAPI interrupt handling cpu to task > mm cpumask. That will be done in a later patch. > > Signed-off-by: Aneesh Kumar K.V Applied to powerpc next, thanks. https://git.kernel.org/powerpc/c/fa4531f753f1c80d21b5eb86ec5c02 cheers