netdev - Re: [PATCH v2 7/7] perf expr: Migrate expr ids table to a hashmap

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Date:   Fri, 15 May 2020 15:59:28 -0700
From:   Ian Rogers <irogers@...gle.com>
To:     Jiri Olsa <jolsa@...hat.com>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        Andrii Nakryiko <andriin@...com>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...omium.org>,
        Kajol Jain <kjain@...ux.ibm.com>,
        Andi Kleen <ak@...ux.intel.com>,
        John Garry <john.garry@...wei.com>,
        Jin Yao <yao.jin@...ux.intel.com>,
        Kan Liang <kan.liang@...ux.intel.com>,
        Cong Wang <xiyou.wangcong@...il.com>,
        Kim Phillips <kim.phillips@....com>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Leo Yan <leo.yan@...aro.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Networking <netdev@...r.kernel.org>, bpf <bpf@...r.kernel.org>,
        Stephane Eranian <eranian@...gle.com>
Subject: Re: [PATCH v2 7/7] perf expr: Migrate expr ids table to a hashmap

On Fri, May 15, 2020 at 3:41 PM Jiri Olsa <jolsa@...hat.com> wrote:
>
> On Fri, May 15, 2020 at 09:50:07AM -0700, Ian Rogers wrote:
>
> SNIP
>
> > diff --git a/tools/perf/util/expr.c b/tools/perf/util/expr.c
> > index 8b4ce704a68d..f64ab91c432b 100644
> > --- a/tools/perf/util/expr.c
> > +++ b/tools/perf/util/expr.c
> > @@ -4,25 +4,76 @@
> >  #include "expr.h"
> >  #include "expr-bison.h"
> >  #include "expr-flex.h"
> > +#include <linux/kernel.h>
> >
> >  #ifdef PARSER_DEBUG
> >  extern int expr_debug;
> >  #endif
> >
> > +static size_t key_hash(const void *key, void *ctx __maybe_unused)
> > +{
> > +     const char *str = (const char *)key;
> > +     size_t hash = 0;
> > +
> > +     while (*str != '\0') {
> > +             hash *= 31;
> > +             hash += *str;
> > +             str++;
> > +     }
> > +     return hash;
> > +}
> > +
> > +static bool key_equal(const void *key1, const void *key2,
> > +                 void *ctx __maybe_unused)
> > +{
> > +     return !strcmp((const char *)key1, (const char *)key2);
>
> should that be strcasecmp ? would it affect the key_hash as well?

The original code does make use of strcasecmp in one place, but in the
group matching (the main useless use for this code) it doesn't. I
don't think it is a regression to keep it as this, and would like a
test case for when it does matter. Is that ok?

Thanks,
Ian

> jirka
>