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Date: Fri, 4 Mar 2016 02:32:00 +0000 From: "Li, Liang Z" <liang.z.li@...el.com> To: Cornelia Huck <cornelia.huck@...ibm.com> CC: "quintela@...hat.com" <quintela@...hat.com>, "amit.shah@...hat.com" <amit.shah@...hat.com>, "qemu-devel@...gnu.org" <qemu-devel@...gnu.org>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, "mst@...hat.com" <mst@...hat.com>, "akpm@...ux-foundation.org" <akpm@...ux-foundation.org>, "pbonzini@...hat.com" <pbonzini@...hat.com>, "rth@...ddle.net" <rth@...ddle.net>, "ehabkost@...hat.com" <ehabkost@...hat.com>, "linux-mm@...ck.org" <linux-mm@...ck.org>, "virtualization@...ts.linux-foundation.org" <virtualization@...ts.linux-foundation.org>, "kvm@...r.kernel.org" <kvm@...r.kernel.org>, "dgilbert@...hat.com" <dgilbert@...hat.com> Subject: RE: [RFC qemu 4/4] migration: filter out guest's free pages in ram bulk stage > On Thu, 3 Mar 2016 18:44:28 +0800 > Liang Li <liang.z.li@...el.com> wrote: > > > Get the free pages information through virtio and filter out the free > > pages in the ram bulk stage. This can significantly reduce the total > > live migration time as well as network traffic. > > > > Signed-off-by: Liang Li <liang.z.li@...el.com> > > --- > > migration/ram.c | 52 > > ++++++++++++++++++++++++++++++++++++++++++++++------ > > 1 file changed, 46 insertions(+), 6 deletions(-) > > > > > @@ -1945,6 +1971,20 @@ static int ram_save_setup(QEMUFile *f, void > *opaque) > > DIRTY_MEMORY_MIGRATION); > > } > > memory_global_dirty_log_start(); > > + > > + if (balloon_free_pages_support() && > > + balloon_get_free_pages(migration_bitmap_rcu->free_pages_bmap, > > + &free_pages_count) == 0) { > > + qemu_mutex_unlock_iothread(); > > + while (balloon_get_free_pages(migration_bitmap_rcu- > >free_pages_bmap, > > + &free_pages_count) == 0) { > > + usleep(1000); > > + } > > + qemu_mutex_lock_iothread(); > > + > > + > > + filter_out_guest_free_pages(migration_bitmap_rcu- > >free_pages_bmap); > > A general comment: Using the ballooner to get information about pages that > can be filtered out is too limited (there may be other ways to do this; we > might be able to use cmma on s390, for example), and I don't like hardcoding > to a specific method. > > What about the reverse approach: Code may register a handler that > populates the free_pages_bitmap which is called during this stage? Good suggestion, thanks! Liang > <I like the idea of filtering in general, but I haven't looked at the code yet> >
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