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SubjectRe: [PATCH 06/14] perf tools: Cache dso data file descriptor
On Tue, May 27, 2014 at 10:05:28AM +0900, Namhyung Kim wrote:
> Hi Jiri,
>
> On Thu, 15 May 2014 19:23:27 +0200, Jiri Olsa wrote:
>
> [SNIP]
> > +static void data_close(void)
> > +{
> > + bool cache_fd = may_cache_fd();
> > +
> > + if (!cache_fd)
> > + close_first_dso();
> > +}
>
> Why do you do this at close()? As long as there's no attempt to open a
> new file, we can keep existing fd, no?

so the way it works now is:

- we keep up to the 'RLIMIT_NOFILE / 2' of open dso objects
- if we try to open dso and it fails, because we are out of
file descriptors, we close dso objects and try to reopen
(check do_open function)
- when we close the dso object we check if number of opened
dso objects is below 'RLIMIT_NOFILE / 2'.. if it is, we keep
the dso opened, if not we close first dso in the list

util/dso.h tries to describe that

>
> > +
> > +void dso__data_close(struct dso *dso)
> > +{
> > + if (dso->data.fd >= 0)
> > + data_close();
> > +}
>
> Hmm.. it's confusing dso__data_close(dso) closes an other dso rather
> than the given dso. And this dso__data_close() is not paired with any
> _open() also these close calls make me confusing which one to use. ;-p

thats due to the caching.. as explained above

About the pairing.. originally the interface was only dso__data_fd
that opened and returned fd, which the caller needed to close.

I added dso__data_close so we could keep track of file descriptors.

I could add dso__data_open I guess, but it is dso__data_fd which is
needed for elf interface anyway.

thanks,
jirka


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