Chunyan and Al,
I suggest that you guys work together to add one of Al's user space API in the demonstration program. That program, along with the user space API specification, can be submitted upstream with the mmap patch. That way people have something to start with and the API, although not official, has the opportunity to be seen and used by the community.
Mathieu
On 7 April 2016 at 07:22, Chunyan Zhang zhang.chunyan@linaro.org wrote:
Hi Al and Ola,
I have fixed the problem of mmap for STM, the kernel code is here [1], the user space example program is on linaro pastebin [2], I have tested the program on my device. If you have any questions, please let me know.
Thanks, Chunyan
[1] https://git.linaro.org/people/zhang.chunyan/linux.git/shortlog/refs/heads/st... [2] https://pastebin.linaro.org/view/21995dfa
On Fri, Apr 1, 2016 at 5:41 PM, Ola Liljedahl Ola.Liljedahl@arm.com wrote:
On 01/04/2016, 11:21, "CoreSight on behalf of Al Grant" <coresight-bounces@lists.linaro.org on behalf of Al.Grant@arm.com> wrote:
Ah, right, using this address (map) directly has some thing wrong for now, I haven't found the root cause. Now I have to focus the work on getting STM driver upstreamed first, and then I will take a look at what caused the problem. I will get back to you once STM mmap() interface works well.
Ok I look forward to it. I think a userspace write API could be quite useful for low-overhead instrumentation. On my Cortex-A57 server I can write a 32-bit STM timestamped data item, guaranteed delivery, from userspace every 30ns. It's not as fast as writing an untimestamped item to a ring buffer in local cache (~1ns) but it's less disruptive on cache, and a lot faster than calling clock_gettime() and writing a timestamped item to a ring buffer (~250ns). And I'm fairly sure that I could make the same API work on Intel STH too although I haven't got one to try out.
I approve of this.
‹ Ola
Al _______________________________________________ CoreSight mailing list CoreSight@lists.linaro.org https://lists.linaro.org/mailman/listinfo/coresight
CoreSight mailing list CoreSight@lists.linaro.org https://lists.linaro.org/mailman/listinfo/coresight