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Groups > linux.kernel > #1406807
| From | "Li, Liang Z" <liang.z.li@intel.com> |
|---|---|
| Newsgroups | linux.kernel |
| Subject | RE: [PATCH RFC kernel] balloon: speed up inflating/deflating process |
| Date | 2016-05-25 12:20 +0200 |
| Message-ID | <rCE4V-8dd-7@gated-at.bofh.it> (permalink) |
| References | (3 earlier) <rChrI-1Tg-11@gated-at.bofh.it> <rCCFQ-7fL-7@gated-at.bofh.it> <rCCPv-7j6-1@gated-at.bofh.it> <rCDix-7HT-5@gated-at.bofh.it> <rCDBT-7Ok-1@gated-at.bofh.it> |
| Organization | linux.* mail to news gateway |
> > > >
> > > > Hi MST,
> > > >
> > > > I have measured the performance when using a 32K page bitmap,
> > >
> > > Just to make sure. Do you mean a 32Kbyte bitmap?
> > > Covering 1Gbyte of memory?
> > Yes.
> >
> > >
> > > > and inflate the balloon to 3GB
> > > > of an idle guest with 4GB RAM.
> > >
> > > Should take 3 requests then, right?
> > >
> >
> > No, we can't assign the PFN when allocating page in balloon driver,
> > So the PFNs of pages allocated may be across a large range, we will
> > tell the host once the pfn_max -pfn_min >= 0x40000(1GB range), so the
> > requests count is most likely to be more than 3.
> >
> > > > Now:
> > > > total inflating time: 338ms
> > > > the count of virtio data transmission: 373
> > >
> > > Why was this so high? I would expect 3 transmissions.
> >
> > I follow your suggestion:
> > ----------------------------------------------------------------------
> > -------------- Suggestion to address all above comments:
> > 1. allocate a bunch of pages and link them up,
> > calculating the min and the max pfn.
> > if max-min exceeds the allocated bitmap size,
> > tell host.
> > 2. limit allocated bitmap size to something reasonable.
> > How about 32Kbytes? This is 256kilo bit in the map, which comes
> > out to 1Giga bytes of memory in the balloon.
> > ----------------------------------------------------------------------
> > --------------- Because the PFNs of the allocated pages are not linear
> > increased, so 3 transmissions are impossible.
> >
> >
> > Liang
>
> Interesting. How about instead of tell host, we do multiple scans, each time
> ignoring pages out of range?
>
> for (pfn = min pfn; pfn < max pfn; pfn += 1G) {
> foreach page
> if page pfn < pfn || page pfn >= pfn + 1G
> continue
> set bit
> tell host
> }
>
That means we have to allocate/free all the requested pages first, and then tell the host.
It works fine for inflating, but for deflating, because the page has been deleted from the vb-> vb_dev_info->pages,
so, we have to use a struct to save the dequeued pages before calling release_pages_balloon(),
I think a page bitmap is the best struct to save these pages, because it consumes less memory.
And that bitmap should be large enough to save pfn 0 to max_pfn.
If the above is true, then we are back to the square one. we really need a large page bitmap. Right?
Liang
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[PATCH RFC kernel] balloon: speed up inflating/deflating process Liang Li <liang.z.li@intel.com> - 2016-05-20 12:10 +0200
Re: [PATCH RFC kernel] balloon: speed up inflating/deflating process Paolo Bonzini <pbonzini@redhat.com> - 2016-05-20 13:30 +0200
RE: [PATCH RFC kernel] balloon: speed up inflating/deflating process "Li, Liang Z" <liang.z.li@intel.com> - 2016-05-24 10:00 +0200
Re: [PATCH RFC kernel] balloon: speed up inflating/deflating process Cornelia Huck <cornelia.huck@de.ibm.com> - 2016-05-20 13:30 +0200
RE: [PATCH RFC kernel] balloon: speed up inflating/deflating process "Li, Liang Z" <liang.z.li@intel.com> - 2016-05-24 09:50 +0200
Re: [PATCH RFC kernel] balloon: speed up inflating/deflating process "Michael S. Tsirkin" <mst@redhat.com> - 2016-05-20 14:10 +0200
RE: [PATCH RFC kernel] balloon: speed up inflating/deflating process "Li, Liang Z" <liang.z.li@intel.com> - 2016-05-24 12:00 +0200
RE: [PATCH RFC kernel] balloon: speed up inflating/deflating process "Li, Liang Z" <liang.z.li@intel.com> - 2016-05-24 12:00 +0200
Re: [PATCH RFC kernel] balloon: speed up inflating/deflating process "Michael S. Tsirkin" <mst@redhat.com> - 2016-05-24 12:10 +0200
RE: [PATCH RFC kernel] balloon: speed up inflating/deflating process "Li, Liang Z" <liang.z.li@intel.com> - 2016-05-24 12:40 +0200
Re: [PATCH RFC kernel] balloon: speed up inflating/deflating process "Michael S. Tsirkin" <mst@redhat.com> - 2016-05-24 13:20 +0200
RE: [PATCH RFC kernel] balloon: speed up inflating/deflating process "Li, Liang Z" <liang.z.li@intel.com> - 2016-05-24 16:40 +0200
Re: [PATCH RFC kernel] balloon: speed up inflating/deflating process "Michael S. Tsirkin" <mst@redhat.com> - 2016-05-24 17:20 +0200
RE: [PATCH RFC kernel] balloon: speed up inflating/deflating process "Li, Liang Z" <liang.z.li@intel.com> - 2016-05-25 03:00 +0200
RE: [PATCH RFC kernel] balloon: speed up inflating/deflating process "Li, Liang Z" <liang.z.li@intel.com> - 2016-05-25 03:10 +0200
Re: [PATCH RFC kernel] balloon: speed up inflating/deflating process "Michael S. Tsirkin" <mst@redhat.com> - 2016-05-25 10:40 +0200
RE: [PATCH RFC kernel] balloon: speed up inflating/deflating process "Li, Liang Z" <liang.z.li@intel.com> - 2016-05-25 10:50 +0200
Re: [PATCH RFC kernel] balloon: speed up inflating/deflating process "Michael S. Tsirkin" <mst@redhat.com> - 2016-05-25 11:00 +0200
RE: [PATCH RFC kernel] balloon: speed up inflating/deflating process "Li, Liang Z" <liang.z.li@intel.com> - 2016-05-25 11:30 +0200
Re: [PATCH RFC kernel] balloon: speed up inflating/deflating process "Michael S. Tsirkin" <mst@redhat.com> - 2016-05-25 11:50 +0200
RE: [PATCH RFC kernel] balloon: speed up inflating/deflating process "Li, Liang Z" <liang.z.li@intel.com> - 2016-05-25 12:20 +0200
Re: [PATCH RFC kernel] balloon: speed up inflating/deflating process "Michael S. Tsirkin" <mst@redhat.com> - 2016-05-25 12:40 +0200
RE: [PATCH RFC kernel] balloon: speed up inflating/deflating process "Li, Liang Z" <liang.z.li@intel.com> - 2016-05-25 16:40 +0200
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