[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH] tools/libxc: Batch memory allocations for PV guests
On Wed, Jun 10, 2015 at 02:38:15PM +0100, Ross Lagerwall wrote: > The current code for allocating memory for PV guests batches the > hypercalls to allocate memory by allocating 1024*1024 extents of order 0 > at a time. To make this faster, first try allocating single extents of > order 9 (2 MiB) before falling back to the order 0 allocating if the > order 9 allocation fails. > > On my test machine this reduced the time to start a 128 GiB PV guest by > about 60 seconds. > > Signed-off-by: Ross Lagerwall <ross.lagerwall@xxxxxxxxxx> > --- > tools/libxc/xc_dom_x86.c | 22 ++++++++++++++++++++-- > 1 file changed, 20 insertions(+), 2 deletions(-) > > diff --git a/tools/libxc/xc_dom_x86.c b/tools/libxc/xc_dom_x86.c > index 783f749..a674d39 100644 > --- a/tools/libxc/xc_dom_x86.c > +++ b/tools/libxc/xc_dom_x86.c > @@ -761,7 +761,7 @@ int arch_setup_meminit(struct xc_dom_image *dom) > { > int rc; > xen_pfn_t pfn, allocsz, mfn, total, pfn_base; > - int i, j; > + int i, j, k; > > rc = x86_compat(dom->xch, dom->guest_domid, dom->guest_type); > if ( rc ) > @@ -881,7 +881,25 @@ int arch_setup_meminit(struct xc_dom_image *dom) > for ( pfn = pfn_base; pfn < pfn_base+pages; pfn++ ) > dom->p2m_host[pfn] = pfn; > > - for ( j = 0; j < pages; j += allocsz ) > + for ( j = 0; j < pages; ) > + { > + if ( (pages - j) < SUPERPAGE_NR_PFNS ) > + break; > + > + mfn = dom->p2m_host[pfn_base + j]; > + rc = xc_domain_populate_physmap(dom->xch, dom->guest_domid, > 1, > + SUPERPAGE_PFN_SHIFT, memflags, &mfn); > + > + if ( rc != 1 ) > + break; > + If you want to optimise you might as well consider batching to reduce the number of hypercall made. See dom->superpages path. Wei. > + for ( k = 0; k < SUPERPAGE_NR_PFNS; k++, j++ ) > + dom->p2m_host[pfn_base + j] = mfn + k; > + } > + > + rc = 0; > + for ( ; j < pages; j += allocsz ) > { > allocsz = pages - j; > if ( allocsz > 1024*1024 ) > -- > 2.1.0 _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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