[Xen-devel] Re: [PATCH] xen: Avoid useless allocation in Xen case.

[Jan Kiszka <jan.kiszka@xxxxxx>]

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 address
> space of the QEMU process.
> 
> So to "avoid" this allocation, the asked tb_size is set to the minimum.
> 
> The other way to do that would be to not call code_gen_alloc when Xen is
> enabled.
> 
> Signed-off-by: Anthony PERARD <anthony.perard@xxxxxxxxxx>
> ---
>  vl.c |    8 ++++++++
>  1 files changed, 8 insertions(+), 0 deletions(-)
> 
> 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)
>          }
>      }
>  
> +    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 for the
> +         * MapCache.
> +         */
> +        tb_size = 1;
> +    }
> +

The same applies to kvm, please generalize.

Jan

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