Re: [Qemu-devel] [PATCH v2 08/27] HACK: Always enable parallel_cpus

[Richard Henderson]

On 09/08/2016 01:39 AM, Alex Bennée wrote:
> 
> Richard Henderson <address@hidden> writes:
> 
>> This is really just a placeholder for an actual
>> command-line switch for mttcg.
>> ---
>>  translate-all.c | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/translate-all.c b/translate-all.c
>> index 99ae7f9..a10fa06 100644
>> --- a/translate-all.c
>> +++ b/translate-all.c
>> @@ -119,7 +119,7 @@ static void *l1_map[V_L1_SIZE];
>>
>>  /* code generation context */
>>  TCGContext tcg_ctx;
>> -bool parallel_cpus;
>> +bool parallel_cpus = 1;
> 
> I appreciate this is currently a hack but for CONFIG_USER it should
> always be true anyway.

One could delay setting parallel_cpus until one of a number of syscalls occur:

(1) clone, with CLONE_VM
(2) mmap, with MAP_SHARED
(3) shmat

which would allow single-threaded programs to run without the atomic overhead.

r~