On Mon, Jun 12, 2023 at 4:17 PM Andrii Nakryiko
<andrii.nakryiko@xxxxxxxxx> wrote:
>
> On Fri, Jun 9, 2023 at 9:12 AM Alexei Starovoitov
> <alexei.starovoitov@xxxxxxxxx> wrote:
> >
> > On Thu, Jun 8, 2023 at 11:32 PM Hou Tao <houtao@xxxxxxxxxxxxxxx> wrote:
> > >
> > > >
> > > >> + --producers=8 --prod-affinity=0-7 "$@")"
> > > > -a -p 8 should just work.
> > > > No need to pick specific cpus.
> > > No. For VM with only 8 CPUs, the affinity of the first producer will be
> > > CPU 1 and the affinity of the last producer will be CPU 8, so the
> > > benchmark will fail to run. But I think I can fix it, so the affinity of
> > > the last producer will be 0 instead.
> >
> > Right. Noticed that too.
> > That should probably be a separate patch to fix this cpu assignment
> > issue in bench for all benchs.
> >
> > Andrii,
> > when you wrote it did you really mean to start assigning cpus from 1
> > or that was just an oversight?
>
> 616 ▸ /* unless explicit producer CPU list is specified, continue after¬
> 617 ▸ * last consumer CPU¬
> 618 ▸ */¬
>
>
> It's been a while, but it seems like each consumer gets its CPU first,
> then each producer. So yeah, seems intentional.
>
> For context, this was done for BPF ringbuf benchmarking, so by default
> I wanted to separate a single consumer from multiple producers.
I see. In this cas Hou's bench has empty consumer:
+static void *htab_mem_consumer(void *arg)
+{
+ return NULL;
+}
but setup_benchmark() still creates an instant 'return NULL' thread
and pins it to cpu 0.
I guess the fix is for htab-mem bench to set env.consumer_cnt = 0
at init time and don't supply empty consumer at all.
May be consumer_cnt=0 can a default and ringbuf bench will just the
default to 1?
