From: "Li, Liang Z" <liang.z.li@intel.com>
To: "Hansen, Dave" <dave.hansen@intel.com>,
David Hildenbrand <david@redhat.com>,
"kvm@vger.kernel.org" <kvm@vger.kernel.org>
Cc: "virtio-dev@lists.oasis-open.org"
<virtio-dev@lists.oasis-open.org>,
"mhocko@suse.com" <mhocko@suse.com>,
"mst@redhat.com" <mst@redhat.com>,
"qemu-devel@nongnu.org" <qemu-devel@nongnu.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"linux-mm@kvack.org" <linux-mm@kvack.org>,
"kirill.shutemov@linux.intel.com"
<kirill.shutemov@linux.intel.com>,
"pbonzini@redhat.com" <pbonzini@redhat.com>,
"akpm@linux-foundation.org" <akpm@linux-foundation.org>,
"virtualization@lists.linux-foundation.org"
<virtualization@lists.linux-foundation.org>,
"dgilbert@redhat.com" <dgilbert@redhat.com>
Subject: RE: [PATCH kernel v5 0/5] Extend virtio-balloon for fast (de)inflating & fast live migration
Date: Fri, 9 Dec 2016 03:09:47 +0000 [thread overview]
Message-ID: <F2CBF3009FA73547804AE4C663CAB28E3A14D246@SHSMSX104.ccr.corp.intel.com> (raw)
In-Reply-To: <f7b47cc4-ee94-bacb-5a17-d049b402263e@intel.com>
> Subject: Re: [PATCH kernel v5 0/5] Extend virtio-balloon for fast (de)inflating
> & fast live migration
>
> On 12/07/2016 05:35 AM, Li, Liang Z wrote:
> >> Am 30.11.2016 um 09:43 schrieb Liang Li:
> >> IOW in real examples, do we have really large consecutive areas or
> >> are all pages just completely distributed over our memory?
> >
> > The buddy system of Linux kernel memory management shows there
> should
> > be quite a lot of consecutive pages as long as there are a portion of
> > free memory in the guest.
> ...
> > If all pages just completely distributed over our memory, it means the
> > memory fragmentation is very serious, the kernel has the mechanism to
> > avoid this happened.
>
> While it is correct that the kernel has anti-fragmentation mechanisms, I don't
> think it invalidates the question as to whether a bitmap would be too sparse
> to be effective.
>
> > In the other hand, the inflating should not happen at this time
> > because the guest is almost 'out of memory'.
>
> I don't think this is correct. Most systems try to run with relatively little free
> memory all the time, using the bulk of it as page cache. We have no reason
> to expect that ballooning will only occur when there is lots of actual free
> memory and that it will not occur when that same memory is in use as page
> cache.
>
Yes.
> In these patches, you're effectively still sending pfns. You're just sending
> one pfn per high-order page which is giving a really nice speedup. IMNHO,
> you're avoiding doing a real bitmap because creating a bitmap means either
> have a really big bitmap, or you would have to do some sorting (or multiple
> passes) of the free lists before populating a smaller bitmap.
>
> Like David, I would still like to see some data on whether the choice between
> bitmaps and pfn lists is ever clearly in favor of bitmaps. You haven't
> convinced me, at least, that the data isn't even worth collecting.
I will try to get some data with the real workload and share it with your guys.
Thanks!
Liang
next prev parent reply other threads:[~2016-12-09 3:09 UTC|newest]
Thread overview: 41+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-11-30 8:43 [PATCH kernel v5 0/5] Extend virtio-balloon for fast (de)inflating & fast live migration Liang Li
2016-11-30 8:43 ` [PATCH kernel v5 1/5] virtio-balloon: rework deflate to add page to a list Liang Li
2016-11-30 8:43 ` [PATCH kernel v5 2/5] virtio-balloon: define new feature bit and head struct Liang Li
2016-11-30 8:43 ` [PATCH kernel v5 3/5] virtio-balloon: speed up inflate/deflate process Liang Li
2016-11-30 8:43 ` [PATCH kernel v5 4/5] virtio-balloon: define flags and head for host request vq Liang Li
2016-11-30 8:43 ` [PATCH kernel v5 5/5] virtio-balloon: tell host vm's unused page info Liang Li
2016-11-30 19:15 ` Dave Hansen
2016-12-04 13:13 ` Li, Liang Z
2016-12-05 17:22 ` Dave Hansen
2016-12-06 4:47 ` Li, Liang Z
2016-12-06 8:40 ` [PATCH kernel v5 0/5] Extend virtio-balloon for fast (de)inflating & fast live migration David Hildenbrand
2016-12-07 13:35 ` Li, Liang Z
2016-12-07 15:34 ` Dave Hansen
2016-12-09 3:09 ` Li, Liang Z [this message]
2016-12-07 15:42 ` David Hildenbrand
2016-12-07 15:45 ` Dave Hansen
2016-12-07 16:21 ` David Hildenbrand
2016-12-07 16:57 ` Dave Hansen
2016-12-07 18:38 ` [Qemu-devel] " Andrea Arcangeli
2016-12-07 18:44 ` Dave Hansen
2016-12-07 18:58 ` Andrea Arcangeli
2016-12-07 19:54 ` Dave Hansen
2016-12-07 20:28 ` Andrea Arcangeli
2016-12-09 4:45 ` Li, Liang Z
2016-12-09 4:53 ` Dave Hansen
2016-12-09 5:35 ` Li, Liang Z
2016-12-09 16:42 ` Andrea Arcangeli
2016-12-14 8:20 ` Li, Liang Z
2016-12-14 8:59 ` Li, Liang Z
2016-12-15 15:34 ` Dave Hansen
2016-12-15 15:54 ` Michael S. Tsirkin
2016-12-16 1:12 ` Li, Liang Z
2016-12-16 15:40 ` Andrea Arcangeli
2016-12-17 11:56 ` Li, Liang Z
2016-12-16 0:48 ` Li, Liang Z
2016-12-16 1:09 ` Dave Hansen
2016-12-16 1:38 ` Li, Liang Z
2016-12-16 1:40 ` Dave Hansen
2016-12-16 1:43 ` Li, Liang Z
2016-12-16 16:01 ` Andrea Arcangeli
2016-12-17 12:39 ` Li, Liang Z
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