Re: [Qemu-devel] [RFC 2/7] translate-all: add out_size field to TranslationBlock

[Richard Henderson]

On 06/29/2017 01:28 PM, Emilio G. Cota wrote:
> Note that due to the cacheline padding we are using, for
> hosts with 64-byte cache lines this will not waste any
> additional memory. Using a s16 would be ideal, since that
> would plug an existing hole in the struct, but I see no
> guarantee that a TB won't overflow it.
>
> Signed-off-by: Emilio G. Cota<address@hidden>
> ---
>   include/exec/exec-all.h   |  1 +
>   accel/tcg/translate-all.c | 16 ++++++++--------
>   2 files changed, 9 insertions(+), 8 deletions(-)
>
> diff --git a/include/exec/exec-all.h b/include/exec/exec-all.h
> index 35a75f1..df12338 100644
> --- a/include/exec/exec-all.h
> +++ b/include/exec/exec-all.h
> @@ -363,6 +363,7 @@ struct TranslationBlock {
>        */
>       uintptr_t jmp_list_next[2];
>       uintptr_t jmp_list_first;
> +    int32_t out_size; /* size of host code for this block */

unsigned probably better.

I do wonder about putting it in the hole after invalid.
Which itself could be shrunk to bool.

I don't believe there's much chance of an overflow of uint16_t.  The limit of 
OPC_BUF_SIZE = 640 fairly well limits the practical size.  And, honestly, it 
doesn't matter if we saturate to 0xffff, so long as you retain the full-size 
gen_code_size local variable.


r~