On 12/04/2013 04:34 PM, Alexey Kardashevskiy wrote:
> On 11/16/2013 03:58 AM, Alexey Kardashevskiy wrote:
>> On 16.11.2013 0:15, Alexander Graf wrote:
>>>
>>>
>>> Am 15.11.2013 um 00:12 schrieb Alexey Kardashevskiy <a...@ozlabs.ru>:
>>>
>>>> At the moment only a whole CPU core can be assigned to a KVM. Since
>>>> POWER7/8 support several threads per core, we want all threads of a core
>>>> to go to the same KVM so every time we run QEMU with -enable-kvm on
>>>> POWER, we have to add -smp X,threads=(4|8)" (4 for POWER7 and
>>>> 8 for POWER8).
>>>>
>>>> This patch tries to read smp_threads number from an accelerator and
>>>> falls back to the default value (1) if the accelerator did not care
>>>> to change it.
>>>>
>>>> Signed-off-by: Alexey Kardashevskiy <a...@ozlabs.ru>
>>>> ---
>>>>
>>>> (!!!)
>>>>
>>>> The usual question - what would be the normal way of doing this?
>>>> What does this patch break? I cannot think of anything right now.
>>>
>>> Is this really what the user wants? On p7 you can run in no-smt, smt2
>>> and smt4 mode. Today we simply default to no-smt. Changing defaults
>>> is usually a bad thing.
>>
>>
>> Defaulting to 1 thread on P7 is a bad thing (other threads stay unused -
>> what is good about this?) and the only reason which I know why it is
>> still threads=1 is that it is hard to make a patch for upstream to
>> change this default.
>>
>>
>> Paul, please, help.
>
>
> Anyone, ping? Thanks.
Everyone ignores me :(
>
>
>>> Alex
>>>
>>>>
>>>>
>>>> ---
>>>> target-ppc/kvm.c | 6 ++++++
>>>> vl.c | 29 ++++++++++++++++-------------
>>>> 2 files changed, 22 insertions(+), 13 deletions(-)
>>>>
>>>> diff --git a/target-ppc/kvm.c b/target-ppc/kvm.c
>>>> index 10d0cd9..80c0386 100644
>>>> --- a/target-ppc/kvm.c
>>>> +++ b/target-ppc/kvm.c
>>>> @@ -109,6 +109,12 @@ int kvm_arch_init(KVMState *s)
>>>> "VM to stall at times!\n");
>>>> }
>>>>
>>>> + if (!smp_threads) {
>>>> + smp_threads = cap_ppc_smt;
>>>> + } else {
>>>> + smp_threads = MIN(smp_threads, cap_ppc_smt);
>>>> + }
>>>> +
>>>> kvm_ppc_register_host_cpu_type();
>>>>
>>>> return 0;
>>>> diff --git a/vl.c b/vl.c
>>>> index 4ad15b8..97fa203 100644
>>>> --- a/vl.c
>>>> +++ b/vl.c
>>>> @@ -210,7 +210,7 @@ int singlestep = 0;
>>>> int smp_cpus = 1;
>>>> int max_cpus = 0;
>>>> int smp_cores = 1;
>>>> -int smp_threads = 1;
>>>> +int smp_threads = 0;
>>>> #ifdef CONFIG_VNC
>>>> const char *vnc_display;
>>>> #endif
>>>> @@ -1395,7 +1395,9 @@ static void smp_parse(QemuOpts *opts)
>>>> if (cpus == 0 || sockets == 0) {
>>>> sockets = sockets > 0 ? sockets : 1;
>>>> cores = cores > 0 ? cores : 1;
>>>> - threads = threads > 0 ? threads : 1;
>>>> + if (!threads) {
>>>> + threads = smp_threads > 0 ? smp_threads : 1;
>>>> + }
>>>> if (cpus == 0) {
>>>> cpus = cores * threads * sockets;
>>>> }
>>>> @@ -1413,7 +1415,8 @@ static void smp_parse(QemuOpts *opts)
>>>> smp_cpus = cpus;
>>>> smp_cores = cores > 0 ? cores : 1;
>>>> smp_threads = threads > 0 ? threads : 1;
>>>> -
>>>> + } else if (!smp_threads) {
>>>> + smp_threads = 1;
>>>> }
>>>>
>>>> if (max_cpus == 0) {
>>>> @@ -3880,16 +3883,6 @@ int main(int argc, char **argv, char **envp)
>>>> data_dir[data_dir_idx++] = CONFIG_QEMU_DATADIR;
>>>> }
>>>>
>>>> - smp_parse(qemu_opts_find(qemu_find_opts("smp-opts"), NULL));
>>>> -
>>>> - machine->max_cpus = machine->max_cpus ?: 1; /* Default to UP */
>>>> - if (smp_cpus > machine->max_cpus) {
>>>> - fprintf(stderr, "Number of SMP cpus requested (%d), exceeds max
>>>> cpus "
>>>> - "supported by machine `%s' (%d)\n", smp_cpus,
>>>> machine->name,
>>>> - machine->max_cpus);
>>>> - exit(1);
>>>> - }
>>>> -
>>>> /*
>>>> * Get the default machine options from the machine if it is not
>>>> already
>>>> * specified either by the configuration file or by the command line.
>>>> @@ -4039,6 +4032,16 @@ int main(int argc, char **argv, char **envp)
>>>>
>>>> configure_accelerator();
>>>>
>>>> + smp_parse(qemu_opts_find(qemu_find_opts("smp-opts"), NULL));
>>>> +
>>>> + machine->max_cpus = machine->max_cpus ?: 1; /* Default to UP */
>>>> + if (smp_cpus > machine->max_cpus) {
>>>> + fprintf(stderr, "Number of SMP cpus requested (%d), exceeds max
>>>> cpus "
>>>> + "supported by machine `%s' (%d)\n", smp_cpus,
>>>> machine->name,
>>>> + machine->max_cpus);
>>>> + exit(1);
>>>> + }
>>>> +
>>>> if (!qtest_enabled() && qtest_chrdev) {
>>>> qtest_init();
>>>> }
>>
>>
>
>
--
Alexey
