From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mailman by lists.gnu.org with tmda-scanned (Exim 4.43) id 1NJvMA-0007yJ-51 for qemu-devel@nongnu.org; Sun, 13 Dec 2009 15:47:54 -0500 Received: from exim by lists.gnu.org with spam-scanned (Exim 4.43) id 1NJvM9-0007xx-9O for qemu-devel@nongnu.org; Sun, 13 Dec 2009 15:47:53 -0500 Received: from [199.232.76.173] (port=52673 helo=monty-python.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1NJvM9-0007xu-1V for qemu-devel@nongnu.org; Sun, 13 Dec 2009 15:47:53 -0500 Received: from hall.aurel32.net ([88.191.82.174]:33798) by monty-python.gnu.org with esmtps (TLS-1.0:RSA_AES_256_CBC_SHA1:32) (Exim 4.60) (envelope-from ) id 1NJvM8-00071I-Mn for qemu-devel@nongnu.org; Sun, 13 Dec 2009 15:47:52 -0500 Date: Sun, 13 Dec 2009 21:47:49 +0100 From: Aurelien Jarno Subject: Re: [Qemu-devel] [PATCH 1/7] alpha: Implement IMB; add placeholders for other userspace PALcalls. Message-ID: <20091213204749.GD4281@volta.aurel32.net> References: <20091213192815.GB4281@volta.aurel32.net> <4B25465A.8090002@twiddle.net> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline In-Reply-To: <4B25465A.8090002@twiddle.net> List-Id: qemu-devel.nongnu.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Richard Henderson Cc: qemu-devel@nongnu.org On Sun, Dec 13, 2009 at 11:54:02AM -0800, Richard Henderson wrote: > On 12/13/2009 11:28 AM, Aurelien Jarno wrote: > >Is it really necessary to flush all the TB here? QEMU should already > >discard TB that have been modified. > > No. But I meant to look into this more carefully with a view to > disabling the other checking within QEMU and speed things up a tad. > It seems to me that the explicit checking with each memory write > ought to only be necessary on architectures like x86 that don't > architecturally require a flush insn to be used. This is actually done only on the first write access to a page and not to each write, so it should not be so costly. It is however something to investigate, as I agree that removing the checks can add some speed-up. > I can drop this fragment if necessary for patch acceptance, however. > I think it is better to drop it until we have a better view of the whole thing. You can add a comment saying that an optimisation might be possible here. -- Aurelien Jarno GPG: 1024D/F1BCDB73 aurelien@aurel32.net http://www.aurel32.net