From: "Li, Liang Z" <liang.z.li@intel.com>
To: "Hansen, Dave" <dave.hansen@intel.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Cc: "virtualization@lists.linux-foundation.org"
<virtualization@lists.linux-foundation.org>,
"linux-mm@kvack.org" <linux-mm@kvack.org>,
"virtio-dev@lists.oasis-open.org"
<virtio-dev@lists.oasis-open.org>,
"kvm@vger.kernel.org" <kvm@vger.kernel.org>,
"qemu-devel@nongnu.org" <qemu-devel@nongnu.org>,
"dgilbert@redhat.com" <dgilbert@redhat.com>,
"quintela@redhat.com" <quintela@redhat.com>,
"Michael S. Tsirkin" <mst@redhat.com>,
Andrew Morton <akpm@linux-foundation.org>,
Vlastimil Babka <vbabka@suse.cz>,
Mel Gorman <mgorman@techsingularity.net>,
Paolo Bonzini <pbonzini@redhat.com>,
"Cornelia Huck" <cornelia.huck@de.ibm.com>,
Amit Shah <amit.shah@redhat.com>
Subject: RE: [PATCH v2 repost 4/7] virtio-balloon: speed up inflate/deflate process
Date: Thu, 28 Jul 2016 01:13:35 +0000 [thread overview]
Message-ID: <F2CBF3009FA73547804AE4C663CAB28E04213CCB@shsmsx102.ccr.corp.intel.com> (raw)
In-Reply-To: <5798DB49.7030803@intel.com>
> Subject: Re: [PATCH v2 repost 4/7] virtio-balloon: speed up inflate/deflate
> process
>
> On 07/26/2016 06:23 PM, Liang Li wrote:
> > + vb->pfn_limit = VIRTIO_BALLOON_PFNS_LIMIT;
> > + vb->pfn_limit = min(vb->pfn_limit, get_max_pfn());
> > + vb->bmap_len = ALIGN(vb->pfn_limit, BITS_PER_LONG) /
> > + BITS_PER_BYTE + 2 * sizeof(unsigned long);
> > + hdr_len = sizeof(struct balloon_bmap_hdr);
> > + vb->bmap_hdr = kzalloc(hdr_len + vb->bmap_len, GFP_KERNEL);
>
> This ends up doing a 1MB kmalloc() right? That seems a _bit_ big. How big
> was the pfn buffer before?
Yes, it is if the max pfn is more than 32GB.
The size of the pfn buffer use before is 256*4 = 1024 Bytes, it's too small,
and it's the main reason for bad performance.
Use the max 1MB kmalloc is a balance between performance and flexibility,
a large page bitmap covers the range of all the memory is no good for a system
with huge amount of memory. If the bitmap is too small, it means we have
to traverse a long list for many times, and it's bad for performance.
Thanks!
Liang
next prev parent reply other threads:[~2016-07-28 1:13 UTC|newest]
Thread overview: 40+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-07-27 1:23 [PATCH v2 repost 0/7] Extend virtio-balloon for fast (de)inflating & fast live migration Liang Li
2016-07-27 1:23 ` [PATCH v2 repost 1/7] virtio-balloon: rework deflate to add page to a list Liang Li
2016-07-27 1:23 ` [PATCH v2 repost 2/7] virtio-balloon: define new feature bit and page bitmap head Liang Li
2016-07-27 1:23 ` [PATCH v2 repost 3/7] mm: add a function to get the max pfn Liang Li
2016-07-27 22:08 ` Michael S. Tsirkin
2016-07-27 22:52 ` Dave Hansen
2016-07-27 1:23 ` [PATCH v2 repost 4/7] virtio-balloon: speed up inflate/deflate process Liang Li
2016-07-27 16:03 ` Dave Hansen
2016-07-27 21:39 ` Michael S. Tsirkin
2016-07-28 3:30 ` Li, Liang Z
2016-07-28 22:15 ` Michael S. Tsirkin
2016-07-29 1:08 ` [virtio-dev] " Li, Liang Z
2016-07-28 1:13 ` Li, Liang Z [this message]
2016-07-28 1:45 ` Michael S. Tsirkin
2016-07-28 6:36 ` [virtio-dev] " Li, Liang Z
2016-07-28 21:51 ` Michael S. Tsirkin
2016-07-29 0:46 ` Li, Liang Z
2016-07-29 19:48 ` Dave Hansen
2016-08-02 0:28 ` Li, Liang Z
2016-07-27 21:36 ` Michael S. Tsirkin
2016-07-28 3:06 ` Li, Liang Z
2016-07-28 22:17 ` Michael S. Tsirkin
2016-07-29 0:38 ` Li, Liang Z
2016-07-27 22:07 ` Michael S. Tsirkin
2016-07-28 3:48 ` Li, Liang Z
2016-07-27 1:23 ` [PATCH v2 repost 5/7] virtio-balloon: define feature bit and head for misc virt queue Liang Li
2016-07-27 1:23 ` [PATCH v2 repost 6/7] mm: add the related functions to get free page info Liang Li
2016-07-27 16:40 ` Dave Hansen
2016-07-27 22:05 ` Michael S. Tsirkin
2016-07-27 22:16 ` Dave Hansen
2016-07-27 23:05 ` Michael S. Tsirkin
2016-07-28 4:36 ` Li, Liang Z
2016-07-28 0:10 ` Li, Liang Z
2016-07-28 0:17 ` Michael S. Tsirkin
2016-07-27 22:13 ` Michael S. Tsirkin
2016-07-28 5:30 ` [virtio-dev] " Li, Liang Z
2016-07-27 1:23 ` [PATCH v2 repost 7/7] virtio-balloon: tell host vm's " Liang Li
2016-07-27 22:00 ` Michael S. Tsirkin
2016-07-28 7:50 ` Li, Liang Z
2016-07-28 21:37 ` Michael S. Tsirkin
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