From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([208.118.235.92]:41742) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1TSrEK-0008Cy-0O for qemu-devel@nongnu.org; Mon, 29 Oct 2012 11:26:24 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1TSrEB-00068U-W5 for qemu-devel@nongnu.org; Mon, 29 Oct 2012 11:26:19 -0400 Received: from mx1.redhat.com ([209.132.183.28]:59574) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1TSrEB-00068I-Ma for qemu-devel@nongnu.org; Mon, 29 Oct 2012 11:26:11 -0400 Message-ID: <508E9FAC.5000106@redhat.com> Date: Mon, 29 Oct 2012 17:24:28 +0200 From: Avi Kivity MIME-Version: 1.0 References: <1350897839-29593-1-git-send-email-pingfank@linux.vnet.ibm.com> <508971E2.9050309@redhat.com> In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [patch v4 00/16] push mmio dispatch out of big lock List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Peter Maydell Cc: Liu Ping Fan , Stefan Hajnoczi , Marcelo Tosatti , qemu-devel@nongnu.org, Anthony Liguori , Jan Kiszka , Paolo Bonzini On 10/25/2012 07:13 PM, Peter Maydell wrote: > On 25 October 2012 18:07, Avi Kivity wrote: >> On 10/25/2012 04:04 PM, Peter Maydell wrote: >>> Is there a clear up to date description somewhere of the design and >>> locking strategy here somewhere? I'd rather not have to try to >>> reconstitute it by reading the whole patchset... >> >> It was described somewhere in a document by Marcelo and myself. >> Basically the goal is to arrive at >> >> address_space_write(): >> rcu_read_lock() >> mr = lookup() >> mr->ref() >> rcu_read_unlock() >> >> mr->dispatch() >> >> mr->unref() >> >> This is the same strategy used in many places in the kernel. > > Yes, but this is rather short on the details Until Jan fleshes this out: > (eg, does every > device have its own lock, No, devices which are not modified will continue to use the BQL. > what are we doing with irqs, Eventually they will gain fine-grained threading too. Until then, they will be protected by the big lock (and any device which calls any irq APIs must hold it). > how about > dma from devices, etc etc). DMA will be unlocked, if done to a device which has its own lock (same as mmio). > It's the details of the design I'd > like to see described... -- error compiling committee.c: too many arguments to function