Re: [PATCH v4 06/53] tools api fs: Switch filename__read_str to use io.h

[Ian Rogers]

On Sun, Nov 5, 2023 at 7:53 PM Namhyung Kim <namhyung@xxxxxxxxxx> wrote:
>
> On Thu, Nov 2, 2023 at 10:58 AM Ian Rogers <irogers@xxxxxxxxxx> wrote:
> >
> > filename__read_str has its own string reading code that allocates
> > memory before reading into it. The memory allocated is sized at BUFSIZ
> > that is 8kb. Most strings are short and so most of this 8kb is
> > wasted.
> >
> > Refactor io__getline so that the newline character can be configurable
> > and ignored in the case of filename__read_str.
> >
> > Code like build_caches_for_cpu in perf's header.c will read many
> > strings and hold them in a data structure, in this case multiple
> > strings per cache level per CPU. Using io.h's io__getline avoids the
> > wasted memory as strings are temporarily read into a buffer on the
> > stack before being copied to a buffer that grows 128 bytes at a time
> > and is never sized larger than the string.
> >
> > For a 16 hyperthread system the memory consumption of "perf record
> > true" is reduced by 180kb, primarily through saving memory when
> > reading the cache information.
> >
> > Signed-off-by: Ian Rogers <irogers@xxxxxxxxxx>
> > ---
>
> [SNIP]
> > diff --git a/tools/lib/api/io.h b/tools/lib/api/io.h
> > index a77b74c5fb65..50d33e14fb56 100644
> > --- a/tools/lib/api/io.h
> > +++ b/tools/lib/api/io.h
> > @@ -141,7 +141,7 @@ static inline int io__get_dec(struct io *io, __u64 *dec)
> >  }
> >
> >  /* Read up to and including the first newline following the pattern of getline. */
>
> You may want to update the comment as well.
>
> > -static inline ssize_t io__getline(struct io *io, char **line_out, size_t *line_len_out)
> > +static inline ssize_t io__getline_nl(struct io *io, char **line_out, size_t *line_len_out, int nl)
>
> How about io__getdelim() similar to POSIX?

Thanks done for v5.

Ian

> Thanks,
> Namhyung
>
>
> >  {
> >         char buf[128];
> >         int buf_pos = 0;
> > @@ -151,7 +151,7 @@ static inline ssize_t io__getline(struct io *io, char **line_out, size_t *line_l
> >
> >         /* TODO: reuse previously allocated memory. */
> >         free(*line_out);
> > -       while (ch != '\n') {
> > +       while (ch != nl) {
> >                 ch = io__get_char(io);
> >
> >                 if (ch < 0)
> > @@ -184,4 +184,9 @@ static inline ssize_t io__getline(struct io *io, char **line_out, size_t *line_l
> >         return -ENOMEM;
> >  }
> >
> > +static inline ssize_t io__getline(struct io *io, char **line_out, size_t *line_len_out)
> > +{
> > +       return io__getline_nl(io, line_out, line_len_out, /*nl=*/'\n');
> > +}
> > +
> >  #endif /* __API_IO__ */
> > --
> > 2.42.0.869.gea05f2083d-goog
> >
>