Quoting Lionel Landwerlin (2018-02-12 11:00:10) > On 12/02/18 10:41, Chris Wilson wrote: > > Quoting Lionel Landwerlin (2018-02-12 10:37:52) > >> On 09/02/18 20:53, Chris Wilson wrote: > >>> Quoting Lionel Landwerlin (2018-02-09 17:47:44) > >>>> Hey Chris, > >>>> > >>>> From the i915/perf point of view, I'm fine with this change. > >>>> The pinning of the hw_id when monitoring a single context (with OA) > >>>> doesn't break the existing userspace (I can only think of Mesa). > >>>> > >>>> I'm also trying to build up a system wide monitoring feature in GPUTop > >>>> with a timeline display. This change makes it a bit more challenging. > >>>> But this isn't really an expected feature, it's just nice to have. > >>>> > >>>> What I'm thinking of would be to keep a circular buffer of requests in > >>>> the order they're submitted to an engine. > >>>> Then the i915 perf driver could correlate between the context-switch > >>>> tagged reports coming from OA and the requests submitted. > >>>> Much like the OA buffer, this circular buffer could overflow at which > >>>> point we signal the application using the i915 perf driver and it'll > >>>> most likely close the driver and try again. > >>>> > >>>> I would need that have the hw_id added to the requests. Does that sounds > >>>> possible? > >>> You already add hw_id to the tracepoint. For the requests, it is just > >>> req->ctx->hw_id, valid from submission to retirement. Hmm, the > >>> tracepoint is broken (use-after-free in ctx->hw_id). What value do you > >>> want for HSW? (This patch will assign all legacy submission to HW ID 0.) > >>> But aiui, for HSW oa you want lrca not HW ID. So both the use-after-free > >>> and alternative ids suggest storing it on the request directly. > >> HSW doesn't have a hw_id field in the OA reports. > >> I'll have to come up with something slightly different. > >> > >>> How do you get the HW ID out, via the tracepoint right? > >> It's in the OA reports. > > I mean how do you correlate the HW ID with userspace? > > -Chris > > > Right now, with tracepoints. But as I wrote above, I don't think it's > reliable (because of the timestamp correlation). > My idea was to let the i915 perf driver do it for userspace by attaching > the pid/tid to the drm_i915_perf_record. > On submission i915 would put the request into a circular buffer and i915 > perf would read back the tail of that buffer to match what is coming out > of the OA unit. And I read that as doing the tracing entirely in userspace. Inside the kernel we should be able to do a much better job of knowing what requests/contexts are active, it may just be we take an extra ref and/or context pin for perf tracking. -Chris _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/intel-gfx
