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Date: Mon, 01 Aug 2011 21:57:34 +0200
From: Jan Kiszka <jan.kiszka@web.de>
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Subject: Re: [Qemu-devel] [PATCH] xen: Avoid useless allocation in Xen case.
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To: Anthony PERARD <anthony.perard@citrix.com>
Cc: Xen Devel <xen-devel@lists.xensource.com>, QEMU-devel <qemu-devel@nongnu.org>, Stefano Stabellini <stefano.stabellini@eu.citrix.com>, Alexander Graf <agraf@suse.de>

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On 2011-08-01 21:26, Anthony PERARD wrote:
> The code_gen_buffer is not use by Xen and can be really big (several
> GB). Even if the host RAM is not used, this buffer just burn the addres=
s
> space of the QEMU process.
>=20
> So to "avoid" this allocation, the asked tb_size is set to the minimum.=

>=20
> The other way to do that would be to not call code_gen_alloc when Xen i=
s
> enabled.
>=20
> Signed-off-by: Anthony PERARD <anthony.perard@citrix.com>
> ---
>  vl.c |    8 ++++++++
>  1 files changed, 8 insertions(+), 0 deletions(-)
>=20
> diff --git a/vl.c b/vl.c
> index d8c7c01..bd60a89 100644
> --- a/vl.c
> +++ b/vl.c
> @@ -3106,6 +3106,14 @@ int main(int argc, char **argv, char **envp)
>          }
>      }
> =20
> +    if (xen_enabled()) {
> +        /* Allocate only the minimum amount of memory for the code_gen=
_buffer.
> +         * Xen does not use it and we need the virtual address space f=
or the
> +         * MapCache.
> +         */
> +        tb_size =3D 1;
> +    }
> +

The same applies to kvm, please generalize.

Jan


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