[igt-dev] [PATCH igt] igt/gem_exec_schedule: Trim max number of contexts used

[Antonio Argenziano]

On 13/02/18 15:10, Chris Wilson wrote:
> Quoting Antonio Argenziano (2018-02-13 22:47:35)
>>
>>
>> On 13/02/18 01:26, Chris Wilson wrote:
>>> icl offers a much reduced context space, and in its simplest setup we
>>> cannot allocate one context per priority level, so trim the number and
>>> reuse the same context for multiple priority requests.
>>>
>>> Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
>>> ---
>>>    tests/gem_exec_schedule.c | 38 +++++++++++++++++++++++---------------
>>>    1 file changed, 23 insertions(+), 15 deletions(-)
>>>
>>> diff --git a/tests/gem_exec_schedule.c b/tests/gem_exec_schedule.c
>>> index 05f7ae38..ec02d994 100644
>>> --- a/tests/gem_exec_schedule.c
>>> +++ b/tests/gem_exec_schedule.c
>>> @@ -43,6 +43,8 @@
>>>    #define BUSY_QLEN 8
>>>    #define MAX_ELSP_QLEN 16
>>>    
>>> +#define MAX_CONTEXTS 256
>>> +
>>>    IGT_TEST_DESCRIPTION("Check that we can control the order of execution");
>>>    
>>>    static void store_dword(int fd, uint32_t ctx, unsigned ring,
>>> @@ -556,8 +558,8 @@ static void preemptive_hang(int fd, unsigned ring)
>>>    static void deep(int fd, unsigned ring)
>>>    {
>>>    #define XS 8
>>> -     const unsigned int nctx = MAX_PRIO - MIN_PRIO;
>>> -     const unsigned size = ALIGN(4*nctx, 4096);
>>> +     const unsigned int nreq = MAX_PRIO - MIN_PRIO;
>>> +     const unsigned size = ALIGN(4*nreq, 4096);
>>>        struct timespec tv = {};
>>>        struct cork cork;
>>>        uint32_t result, dep[XS];
>>> @@ -565,10 +567,9 @@ static void deep(int fd, unsigned ring)
>>>        uint32_t *ptr;
>>>        uint32_t *ctx;
>>>    
>>> -     ctx = malloc(sizeof(*ctx) * nctx);
>>> -     for (int n = 0; n < nctx; n++) {
>>> +     ctx = malloc(sizeof(*ctx) * MAX_CONTEXTS);
>>> +     for (int n = 0; n < MAX_CONTEXTS; n++) {
>>>                ctx[n] = gem_context_create(fd);
>>> -             gem_context_set_priority(fd, ctx[n], MAX_PRIO - nctx + n);
>>>        }
>>>    
>>>        result = gem_create(fd, size);
>>> @@ -592,7 +593,7 @@ static void deep(int fd, unsigned ring)
>>>                execbuf.buffers_ptr = to_user_pointer(obj);
>>>                execbuf.buffer_count = XS + 2;
>>>                execbuf.flags = ring;
>>> -             for (int n = 0; n < nctx; n++) {
>>> +             for (int n = 0; n < MAX_CONTEXTS; n++) {
>>>                        execbuf.rsvd1 = ctx[n];
>>>                        gem_execbuf(fd, &execbuf);
>>>                }
>>> @@ -603,22 +604,29 @@ static void deep(int fd, unsigned ring)
>>>        plug(fd, &cork);
>>>    
>>>        /* Create a deep dependency chain, with a few branches */
>>> -     for (int n = 0; n < nctx && igt_seconds_elapsed(&tv) < 8; n++)
>>> +     for (int n = 0; n < nreq && igt_seconds_elapsed(&tv) < 8; n++) {
>>> +             uint32_t context = ctx[n % MAX_CONTEXTS];
>>
>> Doesn't this introduce some intra-context dependency we didn't have
>> before? Do we care?
> 
> Yes, it reduces the re-ordering possibilities (it will also exercise
> priority inversion within the context as well). We have to reduce the
> test somehow, and this preserves the essence in that the kernel has to
> manage the same long dependencies chains, just now with a few more
> branches.

OK.

Acked-by: Antonio Argenziano <antonio.argenziano at intel.com>

Thanks,
Antonio

> -Chris
>