From mboxrd@z Thu Jan 1 00:00:00 1970 From: Will Deacon Subject: Re: [PATCH] kvmtool: Add parameter to specifiy number of threads in thread_pool Date: Mon, 29 Jun 2015 10:45:03 +0100 Message-ID: <20150629094502.GA17474@arm.com> References: <20150629074544.GA15313@alberich> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: "kvm@vger.kernel.org" To: Andreas Herrmann Return-path: Received: from foss.arm.com ([217.140.101.70]:37383 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751852AbbF2JpI (ORCPT ); Mon, 29 Jun 2015 05:45:08 -0400 Content-Disposition: inline In-Reply-To: <20150629074544.GA15313@alberich> Sender: kvm-owner@vger.kernel.org List-ID: On Mon, Jun 29, 2015 at 08:45:44AM +0100, Andreas Herrmann wrote: > > With current code the number of threads added to the thread_pool > equals number of online CPUs. Thus on an OcteonIII cn78xx system we > usually have 48 threads per guest just for the thread_pool. IMHO this > is overkill for guests that just have a few vCPUs and/or if a guest is > pinned to a subset of host CPUs. E.g. > > # numactl -C 4,5,7,8 ./lkvm run -c 2 -m 256 -k paravirt -d rootfs.ext3 ... > # ps -La | grep threadpool-work | wc -l > 48 > > Don't change default behaviour (for sake of compatibility) but > introduce a new parameter ("-t" or "--threads") that allows to specify > number of threads to be created for the thread_pool: > > # numactl -C 4,5,7,8 ./lkvm run -c 2 -m 256 --threads 4 -k paravirt -d ... > # ps -La | grep threadpool-work | wc -l > 4 We should probably bound this on some minimum value. I assume things go pear-shaped if you pass --threads 1 (or 0, or -1)? Will