Re: [PATCH net-next v3 1/3] selftests/ptr_ring: add benchmark application for ptr_ring

[Yunsheng Lin]

On 2021/7/2 14:43, Jason Wang wrote:
> 
> 在 2021/7/1 下午8:26, Yunsheng Lin 写道:
>> Currently ptr_ring selftest is embedded within the virtio
>> selftest, which involves some specific virtio operation,
>> such as notifying and kicking.
>>
>> As ptr_ring has been used by various subsystems, it deserves
>> it's owner selftest in order to benchmark different usecase
>> of ptr_ring, such as page pool and pfifo_fast qdisc.
>>
>> So add a simple application to benchmark ptr_ring performance.
>> Currently two test mode is supported:
>> Mode 0: Both producing and consuming is done in a single thread,
>>          it is called simple test mode in the test app.
>> Mode 1: Producing and consuming is done in different thread
>>          concurrently, also known as SPSC(single-producer/
>>          single-consumer) test.
>>
>> The multi-producer/single-consumer test for pfifo_fast case is
>> not added yet, which can be added if using CAS atomic operation
>> to enable lockless multi-producer is proved to be better than
>> using r->producer_lock.
>>
>> Signed-off-by: Yunsheng Lin <linyunsheng@xxxxxxxxxx>
>> ---
>> V3: Remove timestamp sampling, use standard C library as much
>>      as possible.

[...]

>> +static void *produce_worker(void *arg)
>> +{
>> +    struct worker_info *info = arg;
>> +    unsigned long i = 0;
>> +    int ret;
>> +
>> +    while (++i <= info->test_count) {
>> +        while (__ptr_ring_full(&ring))
>> +            cpu_relax();
>> +
>> +        ret = __ptr_ring_produce(&ring, (void *)i);
>> +        if (ret) {
>> +            fprintf(stderr, "produce failed: %d\n", ret);
>> +            info->error = true;
>> +            return NULL;
>> +        }
>> +    }
>> +
>> +    info->error = false;
>> +
>> +    return NULL;
>> +}
>> +
>> +static void *consume_worker(void *arg)
>> +{
>> +    struct worker_info *info = arg;
>> +    unsigned long i = 0;
>> +    int *ptr;
>> +
>> +    while (++i <= info->test_count) {
>> +        while (__ptr_ring_empty(&ring))
>> +            cpu_relax();
> 
> 
> Any reason for not simply use __ptr_ring_consume() here?

No particular reason, just to make sure the ring is
non-empty before doing the enqueuing, we could check
if the __ptr_ring_consume() return NULL to decide
the if the ring is empty. Using __ptr_ring_consume()
here enable testing the correctness and performance of
__ptr_ring_consume() too.

> 
> 
>> +
>> +        ptr = __ptr_ring_consume(&ring);
>> +        if ((unsigned long)ptr != i) {
>> +            fprintf(stderr, "consumer failed, ptr: %lu, i: %lu\n",
>> +                (unsigned long)ptr, i);
>> +            info->error = true;
>> +            return NULL;
>> +        }
>> +    }
>> +
>> +    if (!__ptr_ring_empty(&ring)) {
>> +        fprintf(stderr, "ring should be empty, test failed\n");
>> +        info->error = true;
>> +        return NULL;
>> +    }
>> +
>> +    info->error = false;
>> +    return NULL;
>> +}
>> +

[...]

>> +
>> +    return 0;
>> +}
>> diff --git a/tools/testing/selftests/ptr_ring/ptr_ring_test.h b/tools/testing/selftests/ptr_ring/ptr_ring_test.h
>> new file mode 100644
>> index 0000000..32bfefb
>> --- /dev/null
>> +++ b/tools/testing/selftests/ptr_ring/ptr_ring_test.h
> 
> 
> Let's reuse ptr_ring.c in tools/virtio/ringtest. Nothing virt specific there.

It *does* have some virtio specific at the end of ptr_ring.c.
It can be argued that the ptr_ring.c in tools/virtio/ringtest
could be refactored to remove the function related to virtio.

But as mentioned in the previous disscusion [1], the tools/virtio/
seems to have compile error in the latest kernel, it does not seems
right to reuse that. And most of testcase in tools/virtio/ seems
better be in tools/virtio/ringtest instead，so until the testcase
in tools/virtio/ is compile-error-free and moved to tools/testing/
selftests/, it seems better not to reuse it for now.

1. https://patchwork.kernel.org/project/netdevbpf/patch/1624591136-6647-2-git-send-email-linyunsheng@xxxxxxxxxx/#24278945

> 
> Thanks
> 

[...]

> 
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