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    SubjectRe: [PATCH 2/2] vhost: increase default limit of nregions from 64 to 509
    On Wed, 29 Jul 2015 18:28:26 +0300
    "Michael S. Tsirkin" <mst@redhat.com> wrote:

    > On Wed, Jul 29, 2015 at 04:29:23PM +0200, Igor Mammedov wrote:
    > > although now there is vhost module max_mem_regions option
    > > to set custom limit it doesn't help for default setups,
    > > since it requires administrator manually set a higher
    > > limit on each host. Which complicates servers deployments
    > > and management.
    > > Rise limit to the same value as KVM has (509 slots max),
    > > so that default deployments would work out of box.
    > >
    > > Signed-off-by: Igor Mammedov <imammedo@redhat.com>
    > > ---
    > > PS:
    > > Users that would want to lock down vhost could still
    > > use max_mem_regions option to set lower limit, but
    > > I expect it would be minority.
    >
    > I'm not inclined to merge this.
    >
    > Once we change this we can't take it back. It's not a decision
    > to be taken lightly.
    considering that continuous HVA idea has failed, why would you
    want to take limit back in the future if we rise it now?

    >
    > And memory hotplug users are a minority. Out of these, users with a
    > heavily fragmented PA space due to hotplug abuse are an even smaller
    > minority.
    >
    > > ---
    > > include/uapi/linux/vhost.h | 2 +-
    > > 1 file changed, 1 insertion(+), 1 deletion(-)
    > >
    > > diff --git a/include/uapi/linux/vhost.h b/include/uapi/linux/vhost.h
    > > index 2511954..92657bf 100644
    > > --- a/include/uapi/linux/vhost.h
    > > +++ b/include/uapi/linux/vhost.h
    > > @@ -140,7 +140,7 @@ struct vhost_memory {
    > > #define VHOST_MEM_MAX_NREGIONS_NONE 0
    > > /* We support at least as many nregions in VHOST_SET_MEM_TABLE:
    > > * for use on legacy kernels without VHOST_GET_MEM_MAX_NREGIONS support. */
    > > -#define VHOST_MEM_MAX_NREGIONS_DEFAULT 64
    > > +#define VHOST_MEM_MAX_NREGIONS_DEFAULT 509
    > >
    > > /* VHOST_NET specific defines */
    > >
    > > --
    > > 1.8.3.1



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