From: "Michael S. Tsirkin" <mst@redhat.com> To: Dave Hansen <dave.hansen@intel.com> Cc: Alexander Duyck <alexander.duyck@gmail.com>, linux-mm@kvack.org, linux-kernel@vger.kernel.org, kvm@vger.kernel.org, rkrcmar@redhat.com, alexander.h.duyck@linux.intel.com, x86@kernel.org, mingo@redhat.com, bp@alien8.de, hpa@zytor.com, pbonzini@redhat.com, tglx@linutronix.de, akpm@linux-foundation.org Subject: Re: [RFC PATCH 3/4] kvm: Add guest side support for free memory hints Date: Mon, 11 Feb 2019 14:56:39 -0500 Message-ID: <20190211145531-mutt-send-email-mst@kernel.org> (raw) In-Reply-To: <d0610465-1655-1fd0-4847-7a6ba233df85@intel.com> On Mon, Feb 11, 2019 at 10:19:17AM -0800, Dave Hansen wrote: > On 2/11/19 9:58 AM, Michael S. Tsirkin wrote: > >>> Really it seems we want a virtio ring so we can pass a batch of these. > >>> E.g. 256 entries, 2M each - that's more like it. > >> That only makes sense for a system that's doing high-frequency, > >> discontiguous frees of 2M pages. Right now, a 2M free/realloc cycle > >> (THP or hugetlb) is *not* super-high frequency just because of the > >> latency for zeroing the page. > > Heh but with a ton of free memory, and a thread zeroing some of > > it out in the background, will this still be the case? > > It could be that we'll be able to find clean pages > > at all times. > > In a systems where we have some asynchrounous zeroing of memory where > freed, non-zeroed memory is sequestered out of the allocator, yeah, that > could make sense. > > But, that's not what we have today. Right. I wonder whether it's smart to build this assumption into a host/guest interface though. > >> A virtio ring seems like an overblown solution to a non-existent problem. > > It would be nice to see some traces to help us decide one way or the other. > > Yeah, agreed. Sounds like we need some more testing to see if these > approaches hit bottlenecks anywhere.
next prev parent reply index Thread overview: 55+ messages / expand[flat|nested] mbox.gz Atom feed top 2019-02-04 18:15 [RFC PATCH 0/4] kvm: Report unused guest pages to host Alexander Duyck 2019-02-04 18:15 ` [RFC PATCH 1/4] madvise: Expose ability to set dontneed from kernel Alexander Duyck 2019-02-04 18:15 ` [RFC PATCH 2/4] kvm: Add host side support for free memory hints Alexander Duyck 2019-02-10 0:44 ` Michael S. Tsirkin 2019-02-11 17:34 ` Alexander Duyck 2019-02-11 17:36 ` Michael S. Tsirkin 2019-02-11 17:41 ` Dave Hansen 2019-02-11 17:48 ` Michael S. Tsirkin 2019-02-11 18:30 ` Alexander Duyck 2019-02-11 19:24 ` Michael S. Tsirkin 2019-02-04 18:15 ` [RFC PATCH 3/4] kvm: Add guest " Alexander Duyck 2019-02-04 19:44 ` Dave Hansen 2019-02-04 20:42 ` Alexander Duyck 2019-02-04 23:00 ` Nadav Amit 2019-02-04 23:37 ` Alexander Duyck 2019-02-05 0:03 ` Nadav Amit 2019-02-05 0:16 ` Alexander Duyck 2019-02-05 1:46 ` Nadav Amit 2019-02-05 18:09 ` Alexander Duyck 2019-02-07 18:21 ` Luiz Capitulino 2019-02-07 18:44 ` Alexander Duyck 2019-02-07 20:02 ` Luiz Capitulino 2019-02-08 21:05 ` Nitesh Narayan Lal 2019-02-08 21:31 ` Alexander Duyck 2019-02-10 0:49 ` Michael S. Tsirkin 2019-02-11 16:31 ` Alexander Duyck 2019-02-11 17:36 ` Michael S. Tsirkin 2019-02-11 18:10 ` Alexander Duyck 2019-02-11 19:54 ` Michael S. Tsirkin 2019-02-11 21:00 ` Alexander Duyck 2019-02-11 22:52 ` Michael S. Tsirkin [not found] ` <94462313ccd927d25675f69de459456cf066c1a2.camel@linux.intel.com> 2019-02-12 0:34 ` Michael S. Tsirkin 2019-02-11 17:48 ` Dave Hansen 2019-02-11 17:58 ` Michael S. Tsirkin 2019-02-11 18:19 ` Dave Hansen 2019-02-11 19:56 ` Michael S. Tsirkin [this message] 2019-02-04 18:15 ` [RFC PATCH 4/4] mm: Add merge page notifier Alexander Duyck 2019-02-04 19:40 ` Dave Hansen 2019-02-04 19:51 ` Alexander Duyck 2019-02-10 0:57 ` Michael S. Tsirkin 2019-02-11 13:30 ` Nitesh Narayan Lal 2019-02-11 14:17 ` Michael S. Tsirkin 2019-02-11 16:24 ` Nitesh Narayan Lal 2019-02-11 17:41 ` Michael S. Tsirkin 2019-02-11 18:09 ` Nitesh Narayan Lal 2019-02-11 6:40 ` Aaron Lu 2019-02-11 15:58 ` Alexander Duyck 2019-02-12 2:09 ` Aaron Lu 2019-02-12 17:20 ` Alexander Duyck 2019-02-04 18:19 ` [RFC PATCH QEMU] i386/kvm: Enable paravirtual unused page hint mechanism Alexander Duyck 2019-02-05 17:25 ` [RFC PATCH 0/4] kvm: Report unused guest pages to host Nitesh Narayan Lal 2019-02-05 18:43 ` Alexander Duyck 2019-02-07 14:48 ` Nitesh Narayan Lal 2019-02-07 16:56 ` Alexander Duyck 2019-02-10 0:51 ` Michael S. Tsirkin
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