Hi Elijah,
On Thu, 27 Jan 2022, Elijah Newren wrote:
> On Wed, Jan 26, 2022 at 3:37 PM Matthew John Cheetham via GitGitGadget
> <gitgitgadget@xxxxxxxxx> wrote:
> >
> > From: Matthew John Cheetham <mjcheetham@xxxxxxxxxxx>
> >
> > When operating at the scale that Scalar wants to support, certain data
> > shapes are more likely to cause undesirable performance issues, such as
> > large numbers or large sizes of loose objects.
>
> Makes sense.
>
> > By including statistics about this, `scalar diagnose` now makes it
> > easier to identify such scenarios.
> >
> > Signed-off-by: Matthew John Cheetham <mjcheetham@xxxxxxxxxxx>
> > ---
> > contrib/scalar/scalar.c | 60 ++++++++++++++++++++++++++++++++
> > contrib/scalar/t/t9099-scalar.sh | 2 ++
> > 2 files changed, 62 insertions(+)
> >
> > diff --git a/contrib/scalar/scalar.c b/contrib/scalar/scalar.c
> > index 690933ffdf3..c0ad4948215 100644
> > --- a/contrib/scalar/scalar.c
> > +++ b/contrib/scalar/scalar.c
> > @@ -686,6 +686,60 @@ static void dir_file_stats(struct strbuf *buf, const char *path)
> > closedir(dir);
> > }
> >
> > +static int count_files(char *path)
> > +{
> > + DIR *dir = opendir(path);
> > + struct dirent *e;
> > + int count = 0;
> > +
> > + if (!dir)
> > + return 0;
> > +
> > + while ((e = readdir(dir)) != NULL)
> > + if (!is_dot_or_dotdot(e->d_name) && e->d_type == DT_REG)
> > + count++;
> > +
> > + closedir(dir);
> > + return count;
> > +}
> > +
> > +static void loose_objs_stats(struct strbuf *buf, const char *path)
> > +{
> > + DIR *dir = opendir(path);
> > + struct dirent *e;
> > + int count;
> > + int total = 0;
> > + unsigned char c;
> > + struct strbuf count_path = STRBUF_INIT;
> > + size_t base_path_len;
> > +
> > + if (!dir)
> > + return;
> > +
> > + strbuf_addstr(buf, "Object directory stats for ");
> > + strbuf_add_absolute_path(buf, path);
> > + strbuf_addstr(buf, ":\n");
> > +
> > + strbuf_add_absolute_path(&count_path, path);
> > + strbuf_addch(&count_path, '/');
> > + base_path_len = count_path.len;
> > +
> > + while ((e = readdir(dir)) != NULL)
> > + if (!is_dot_or_dotdot(e->d_name) &&
> > + e->d_type == DT_DIR && strlen(e->d_name) == 2 &&
> > + !hex_to_bytes(&c, e->d_name, 1)) {
>
> You only recurse into directories, ignoring individual files.
>
> > + strbuf_setlen(&count_path, base_path_len);
> > + strbuf_addstr(&count_path, e->d_name);
> > + total += (count = count_files(count_path.buf));
> > + strbuf_addf(buf, "%s : %7d files\n", e->d_name, count);
>
> This shows the number of files within a directory.
>
> > + }
> > +
> > + strbuf_addf(buf, "Total: %d loose objects", total);
>
> and this shows the total number of files across all the directories.
>
> But the commit message suggested you also wanted to check for large
> sizes of loose objects. Did that get ripped out at some point with
> the commit message not being updated, or is it perhaps going to be
> included later?
No, there was no plan to include this information later, as the original
.NET implementation of `scalar diagnose` did not provide that information,
either (which I take as a strong sign that we never needed this type of
information to help users, at least not up until this point).
Besides, it would be kind of a difficult thing to say conclusively what
makes a loose file "big". Is it the zlib-compressed size on disk? Or the
unpacked size? Should there be a configurable threshold to determine when
an object is big? Should `core.bigFileThreshold` be co-opted for this?
Together with the fact that there was no need for this information in
practice, it makes me doubt that we should add this type of information. I
actually suspect that _iff_ information of that type would be helpful, a
more complete tool like git-sizer (https://github.com/github/git-sizer/)
would be needed, and I do not really want to subsume git-sizer's
functionality in `scalar diagnose`.
I rephrased the commit message.
Ciao,
Dscho
>
> > +
> > + strbuf_release(&count_path);
> > + closedir(dir);
> > +}
> > +
> > static int cmd_diagnose(int argc, const char **argv)
> > {
> > struct option options[] = {
> > @@ -734,6 +788,12 @@ static int cmd_diagnose(int argc, const char **argv)
> > if ((res = stage(tmp_dir.buf, &buf, "packs-local.txt")))
> > goto diagnose_cleanup;
> >
> > + strbuf_reset(&buf);
> > + loose_objs_stats(&buf, ".git/objects");
> > +
> > + if ((res = stage(tmp_dir.buf, &buf, "objects-local.txt")))
> > + goto diagnose_cleanup;
> > +
> > if ((res = stage_directory(tmp_dir.buf, ".git", 0)) ||
> > (res = stage_directory(tmp_dir.buf, ".git/hooks", 0)) ||
> > (res = stage_directory(tmp_dir.buf, ".git/info", 0)) ||
> > diff --git a/contrib/scalar/t/t9099-scalar.sh b/contrib/scalar/t/t9099-scalar.sh
> > index b1745851e31..f2ec156d819 100755
> > --- a/contrib/scalar/t/t9099-scalar.sh
> > +++ b/contrib/scalar/t/t9099-scalar.sh
> > @@ -77,6 +77,8 @@ test_expect_success UNZIP 'scalar diagnose' '
> > unzip -p "$zip_path" diagnostics.log >out &&
> > test_file_not_empty out &&
> > unzip -p "$zip_path" packs-local.txt >out &&
> > + test_file_not_empty out &&
> > + unzip -p "$zip_path" objects-local.txt >out &&
> > test_file_not_empty out
> > '
> >
> > --
> > gitgitgadget
>
