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SubjectRe: [PATCH 5/9] perf utils: add support for arch standard events
On Thu, Feb 08, 2018 at 02:45:37PM +0000, John Garry wrote:
> On 08/02/2018 13:55, Jiri Olsa wrote:
> > On Wed, Feb 07, 2018 at 01:45:00AM +0800, John Garry wrote:
> >
> > SNIP
> >
> > > + char *perpkg;
> > > + char *unit;
> > > + char *metric_expr;
> > > + char *metric_name;
> > > + char *metric_group;
> > > + struct list_head list;
> > > + char strings[];
> > > +};
> > > +
> > > +static LIST_HEAD(arch_std_events);
> > > +
> > > +#define ADD_EVENT_STRING(string) do { if (string) { \
> > > + es->string = strings; \
> > > + strings += snprintf(strings, len, "%s", string) + 1; \
> > > +} } while (0)
> > > +
> > > +static int save_arch_std_events(void *data, char *name, char *event,
> > > + char *desc, char *long_desc, char *pmu,
> > > + char *unit, char *perpkg, char *metric_expr,
> > > + char *metric_name, char *metric_group)
> > > +{
> > > + struct event_struct *es;
> > > + struct stat *sb = data;
> > > + int len;
> > > + char *strings;
> > > +
> > > + /*
> > > + * Lazily allocate size of the json file to hold the
> > > + * strings, which would be more than large enough.
> > > + */
> > > + len = sb->st_size;
> > > +
> > > + es = malloc(sizeof(*es) + len);
> >
> > hum, so for single event you allocate buffer of the size
> > of the entire file this event is defined in?
> >
> > what do I miss? I assume there're more of those arch-defined
> > events defined in the single file..
>
> Hi Jirka,
>
> Yes, allocating the file size per event was just to make the code more
> concise (instead of finding each string length), but obviously it is an
> inefficient practice in terms of memory usage.
>
> But since the JSONs are generally not huge, and in practice we would only be
> accessing a fraction of the buffer's physical memory to save the event
> strings, I thought it ok.
>
> Anyway, I'll see if there is something more efficient I can do.

maybe the json parser could provide the overall lenght?

jirka

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