From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: virtio-dev-return-6214-cohuck=redhat.com@lists.oasis-open.org Sender: List-Post: List-Help: List-Unsubscribe: List-Subscribe: Received: from lists.oasis-open.org (oasis-open.org [10.110.1.242]) by lists.oasis-open.org (Postfix) with ESMTP id B187D985D49 for ; Wed, 9 Oct 2019 15:21:45 +0000 (UTC) From: Nitesh Narayan Lal References: <20191001152441.27008.99285.stgit@localhost.localdomain> <7233498c-2f64-d661-4981-707b59c78fd5@redhat.com> <1ea1a4e11617291062db81f65745b9c95fd0bb30.camel@linux.intel.com> <8bd303a6-6e50-b2dc-19ab-4c3f176c4b02@redhat.com> <0a16b11e-ec3b-7196-5b7f-e7395876cf28@redhat.com> <7fc13837-546c-9c4a-1456-753df199e171@redhat.com> <5b6e0b6df46c03bfac906313071ac0362d43c432.camel@linux.intel.com> Message-ID: <5c640ecb-cfef-2fa6-57aa-1352f1036f4e@redhat.com> Date: Wed, 9 Oct 2019 11:21:34 -0400 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Content-Language: en-US Subject: [virtio-dev] Re: [PATCH v11 0/6] mm / virtio: Provide support for unused page reporting To: Alexander Duyck Cc: LKML , linux-mm , Alexander Duyck , David Hildenbrand , virtio-dev@lists.oasis-open.org, kvm list , "Michael S. Tsirkin" , Dave Hansen , Matthew Wilcox , Michal Hocko , Andrew Morton , Mel Gorman , Vlastimil Babka , Oscar Salvador , Yang Zhang , Pankaj Gupta , Konrad Rzeszutek Wilk , Rik van Riel , lcapitulino@redhat.com, "Wang, Wei W" , Andrea Arcangeli , Paolo Bonzini , Dan Williams List-ID: On 10/7/19 1:06 PM, Nitesh Narayan Lal wrote: [...] >> So what was the size of your guest? One thing that just occurred to me= is >> that you might be running a much smaller guest than I was. > I am running a 30 GB guest. > >>>> If so I would have expected a much higher difference versus >>>> baseline as zeroing/faulting the pages in the host gets expensive fa= irly >>>> quick. What is the host kernel you are running your test on? I'm jus= t >>>> wondering if there is some additional overhead currently limiting yo= ur >>>> setup. My host kernel was just the same kernel I was running in the = guest, >>>> just built without the patches applied. >>> Right now I have a different host-kernel. I can install the same kern= el to the >>> host as well and see if that changes anything. >> The host kernel will have a fairly significant impact as I recall. For= >> example running a stock CentOS kernel lowered the performance compared= to >> running a linux-next kernel. As a result the numbers looked better sin= ce >> the overall baseline was lower to begin with as the host OS was >> introducing additional overhead. > I see in that case I will try by installing the same guest kernel > to the host as well. As per your suggestion, I tried replacing the host kernel with an upstream kernel without my patches i.e., my host has a kernel built on to= p of the upstream kernel's master branch which has Sept 23rd commit and the= guest has the same kernel for the no-hinting case and same kernel + my patches for the page reporting case. With the changes reported earlier on top of v12, I am not seeing any furt= her degradation (other than what I have previously reported). To be sure that THP is actively used, I did an experiment where I changed= the MEMSIZE in the page_fault. On doing so THP usage checked via /proc/meminf= o also increased as I expected. In any case, if you find something else please let me know and I will loo= k into it again. I am still looking into your suggestion about cache line bouncing and wil= l reply to it, if I have more questions. [...] --=20 Thanks Nitesh --------------------------------------------------------------------- To unsubscribe, e-mail: virtio-dev-unsubscribe@lists.oasis-open.org For additional commands, e-mail: virtio-dev-help@lists.oasis-open.org