From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:56678) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1dpW7G-0000YN-Dm for qemu-devel@nongnu.org; Wed, 06 Sep 2017 04:55:23 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1dpW7D-0007IE-Sq for qemu-devel@nongnu.org; Wed, 06 Sep 2017 04:55:22 -0400 Received: from mail-wm0-x22f.google.com ([2a00:1450:400c:c09::22f]:35220) by eggs.gnu.org with esmtps (TLS1.0:RSA_AES_128_CBC_SHA1:16) (Exim 4.71) (envelope-from ) id 1dpW7D-0007HB-Jw for qemu-devel@nongnu.org; Wed, 06 Sep 2017 04:55:19 -0400 Received: by mail-wm0-x22f.google.com with SMTP id f199so6831338wme.0 for ; Wed, 06 Sep 2017 01:55:17 -0700 (PDT) References: <20170829172326.1131-1-bobby.prani@gmail.com> <8ea5a586-4d19-82db-f4b7-058229dc4124@twiddle.net> From: Alex =?utf-8?Q?Benn=C3=A9e?= In-reply-to: <8ea5a586-4d19-82db-f4b7-058229dc4124@twiddle.net> Date: Wed, 06 Sep 2017 09:55:15 +0100 Message-ID: <87ingwmcjw.fsf@linaro.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Subject: Re: [Qemu-devel] [PATCH] tcg/softmmu: Increase size of TLB caches List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Richard Henderson Cc: Pranith Kumar , qemu-devel Richard Henderson writes: > On 09/05/2017 05:33 PM, Pranith Kumar wrote: >>> This significantly degrades performance of alpha-softmmu. >>> It spends about 25% of all cpu time in memset. >> >> What workload does it degrade for? I will try to reproduce and see >> which memset is causing this. > > emerge --update --ask @world > > which is a lot of python, iirc. > > It is the tlb flush memset that is causing this. > The tlb has grown from a few kB to 300kB with your patch. Hmm I wonder if this is QEMU doing global flushes which could actually be partial TLB flushes? emerge is quite a memory hog though so its conceivable we are generating a lot of churn as it runs. -- Alex Bennée