From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail138.messagelabs.com (mail138.messagelabs.com [216.82.249.35]) by kanga.kvack.org (Postfix) with ESMTP id DEFEA6B004A for ; Wed, 15 Sep 2010 09:20:32 -0400 (EDT) Received: from d23relay05.au.ibm.com (d23relay05.au.ibm.com [202.81.31.247]) by e23smtp02.au.ibm.com (8.14.4/8.13.1) with ESMTP id o8FDGBE5025184 for ; Wed, 15 Sep 2010 23:16:11 +1000 Received: from d23av03.au.ibm.com (d23av03.au.ibm.com [9.190.234.97]) by d23relay05.au.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id o8FDKTqM1032330 for ; Wed, 15 Sep 2010 23:20:29 +1000 Received: from d23av03.au.ibm.com (loopback [127.0.0.1]) by d23av03.au.ibm.com (8.14.4/8.13.1/NCO v10.0 AVout) with ESMTP id o8FDKS0q010015 for ; Wed, 15 Sep 2010 23:20:29 +1000 Date: Wed, 15 Sep 2010 22:50:19 +0930 From: Christopher Yeoh Subject: Re: [RFC][PATCH] Cross Memory Attach Message-ID: <20100915225019.4ca665fc@lilo> In-Reply-To: <20100915080235.GA13152@elte.hu> References: <20100915104855.41de3ebf@lilo> <20100915080235.GA13152@elte.hu> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org To: Ingo Molnar Cc: linux-kernel@vger.kernel.org, Andrew Morton , Linus Torvalds , Peter Zijlstra , linux-mm@kvack.org List-ID: On Wed, 15 Sep 2010 10:02:35 +0200 Ingo Molnar wrote: > > What did those OpenMPI facilities use before your patch - shared > memory or sockets? This comparison is against OpenMPI using the shared memory btl. > I have an observation about the interface: > > A small detail: 'int flags' should probably be 'unsigned long flags' > - it leaves more space. ok. > Also, note that there is a further performance optimization possible > here: if the other task's ->mm is the same as this task's (they share > the MM), then the copy can be done straight in this process context, > without GUP. User-space might not necessarily be aware of this so it > might make sense to express this special case in the kernel too. ok. > More fundamentally, wouldnt it make sense to create an iovec > interface here? If the Gather(v) / Scatter(v) / AlltoAll(v) workloads > have any fragmentation on the user-space buffer side then the copy of > multiple areas could be done in a single syscall. (the MM lock has to > be touched only once, target task only be looked up only once, etc.) yes, I think so. Currently where I'm using the interface in OpenMPI I can't take advantage of this, but it could be changed in the future- and its likely other MPI's could take advantage of it already. > Plus, a small naming detail, shouldnt the naming be more IO like: > > sys_process_vm_read() > sys_process_vm_write() Yes, that looks better to me. I really wasn't sure how to name them. Regards, Chris -- cyeoh@au.ibm.com -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org