Re: [PATCH 2/6] pstore: Add event tracing support

[Sai Prakash Ranjan]

On 9/26/2018 2:10 AM, Joel Fernandes wrote:
> On Tue, Sep 25, 2018 at 1:39 PM, Joel Fernandes <joelaf@xxxxxxxxxx> wrote:
> > On Tue, Sep 25, 2018 at 1:37 PM, Joel Fernandes <joelaf@xxxxxxxxxx> wrote:
> > > On Sun, Sep 23, 2018 at 8:33 AM, Sai Prakash Ranjan
> > > <saiprakash.ranjan@xxxxxxxxxxxxxx> wrote:
> > > > On 9/22/2018 10:07 PM, Sai Prakash Ranjan wrote:
> > > > > On 9/22/2018 2:35 PM, Joel Fernandes wrote:
> > > > > > On Sat, Sep 8, 2018 at 4:28 PM Sai Prakash Ranjan
> > > > > > <saiprakash.ranjan@xxxxxxxxxxxxxx> wrote:
> > > > > > > +
> > > > > > > +       trace_seq_init(&iter->seq);
> > > > > > > +       iter->ent = fbuffer->entry;
> > > > > > > +       event_call->event.funcs->trace(iter, 0, event);
> > > > > > > +       trace_seq_putc(&iter->seq, 0);
> > > > > >
> > > > > >
> > > > > > Would it be possible to store the binary trace record in the pstore
> > > > > > buffer instead of outputting text? I suspect that will both be faster
> > > > > > and less space.
> > > > >
> > > > > I will try this and come back.
> > > >
> > > > Hi Joel,
> > > >
> > > > I removed trace_seq_putc and there is some improvement seen: 203 MB/s
> > > >
> > > > # dd if=/dev/zero of=/dev/null status=progress
> > > > 12207371264 bytes (12 GB, 11 GiB) copied, 60 s, 203 MB/s^C
> > > > 24171926+0 records in
> > > > 24171926+0 records out
> > > > 12376026112 bytes (12 GB, 12 GiB) copied, 60.8282 s, 203 MB/s
> > > >
> > > > This seems good when compared to 190 MB/s seen previously.
> > > > If this is Ok, then I will spin v2 with changes suggested.
> > >
> > > Sorry for slow reply, yes that sounds good and a worthwhile perf improvement.
> >
> > Well so I think you should still not use spinlock to synchronize and
> > split the buffer. You could expand pstore_record to have a ts field or
> > introduce a new API like ->write_percpu instead of write, or
> > something. But I strongly feel you should lock. For ftrace function
>
> Aargh, I meant you should *not* lock :-)

OK I can try this and will measure some perf difference.

BTW I guess you missed my previous comment about not able to combine 
logs based on timestamp? Anyways I think if I add some extra ts field, 
then should be able to do it.

Thanks,
Sai

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