linux-kernel - Re: [PATCH v3 3/7] perf evsel: Add iterator to iterate over events ordered by CPU

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Message-ID: <20191101083822.GA4763@krava>
Date:   Fri, 1 Nov 2019 09:38:22 +0100
From:   Jiri Olsa <jolsa@...hat.com>
To:     Andi Kleen <andi@...stfloor.org>
Cc:     acme@...nel.org, jolsa@...nel.org, eranian@...gle.com,
        linux-kernel@...r.kernel.org, Andi Kleen <ak@...ux.intel.com>
Subject: Re: [PATCH v3 3/7] perf evsel: Add iterator to iterate over events
 ordered by CPU

On Wed, Oct 30, 2019 at 12:03:28PM -0700, Andi Kleen wrote:
> > 
> > > The exists evlist->cpus cannot be used (I tried that)
> > > I also don't think we have an existing function to merge
> > > two maps, so that would need to be added to create it.
> > > Just using ->cpu_index is a much simpler change.
> > 
> > I dont think that would be lot of code
> > and it would simplify this one
> 
> AFAIK they're not guaranteed to be sorted, which makes merging
> complicated. I'm not sure it's safe to just sort existing maps
> because someone might have a index.

we could add bitmap to maps, then combining them
would be just a matter of or-ing them

> 
> So you'll need to create temporary maps, sort them and then 
> merge. Won't be simple.

it's also not simple to read simple event close code now

jirka