On Mon, Mar 24, 2014 at 02:36:22PM -0700, Junio C Hamano wrote:
> Kirill Smelkov <[email protected]> writes:
>
> > The downside is that try_to_follow_renames(), if active, we cause
> > re-reading of 2 initial trees, which was negligible based on my timings,
>
> That would depend on how often the codepath triggered in your test
> case, but is totally understandable. It fires only when the path we
> have been following disappears from the parent, and the processing
> of try-to-follow itself is very compute-intensive (it needs to run
> find-copies-harder logic) that will end up reading many subtrees of
> the two initial trees; two more reading of tree objects will be
> dwarfed by the actual processing.
I agree and thanks for the explanation.
> > and which is outweighed cogently by the upsides.
>
> > Changes since v1:
> >
> > - don't need to touch diff.h, as diff_tree() became static.
>
> Nice. I wonder if it is an option to let the function keep its name
> diff_tree() without renaming it to __diff_tree_whatever(), though.
As I see it, in Git for functions operating on trees, there is convention
to accept either `struct tree_desc *` and be named simply, or sha1 and
be named with _sha1 suffix. From this point of view for new diff_tree()
accepting sha1's and staying with its old name would be confusing.
Besides, in the end we'll have two function with high-level wrapper, and
lower-lever worker:
- diff_tree_sha1(), and
- diff_tree_paths().
So it's not about this only particular case. Both do some simple
preparation, call worker, and perform some cleanup.
So the question is how to name the worker?
In Linux they use "__" prefix. We could also use some other prefix or
suffix, e.g. "_bh" (for bottom-half), "_worker", "_low", "_raw", etc...
To me, personally, the cleanest is "__" prefix, but maybe I'm too used
to Linux etc... I'm open to other naming scheme, only it should be
consistent.
What are the downsides of "__" prefix by the way?
> > tree-diff.c | 60
> > ++++++++++++++++++++++++++++--------------------------------
> > 1 file changed, 28 insertions(+), 32 deletions(-)
> >
> > diff --git a/tree-diff.c b/tree-diff.c
> > index b99622c..f90acf5 100644
> > --- a/tree-diff.c
> > +++ b/tree-diff.c
> > @@ -137,12 +137,17 @@ static void skip_uninteresting(struct tree_desc *t,
> > struct strbuf *base,
> > }
> > }
> >
> > -static int diff_tree(struct tree_desc *t1, struct tree_desc *t2,
> > - const char *base_str, struct diff_options *opt)
> > +static int __diff_tree_sha1(const unsigned char *old, const unsigned char
> > *new,
> > + const char *base_str, struct diff_options *opt)
> > {
> > + struct tree_desc t1, t2;
> > + void *t1tree, *t2tree;
> > struct strbuf base;
> > int baselen = strlen(base_str);
> >
> > + t1tree = fill_tree_descriptor(&t1, old);
> > + t2tree = fill_tree_descriptor(&t2, new);
> > +
> > /* Enable recursion indefinitely */
> > opt->pathspec.recursive = DIFF_OPT_TST(opt, RECURSIVE);
> >
> > @@ -155,39 +160,41 @@ static int diff_tree(struct tree_desc *t1, struct
> > tree_desc *t2,
> > if (diff_can_quit_early(opt))
> > break;
> > if (opt->pathspec.nr) {
> > - skip_uninteresting(t1, &base, opt);
> > - skip_uninteresting(t2, &base, opt);
> > + skip_uninteresting(&t1, &base, opt);
> > + skip_uninteresting(&t2, &base, opt);
> > }
> > - if (!t1->size && !t2->size)
> > + if (!t1.size && !t2.size)
> > break;
> >
> > - cmp = tree_entry_pathcmp(t1, t2);
> > + cmp = tree_entry_pathcmp(&t1, &t2);
> >
> > /* t1 = t2 */
> > if (cmp == 0) {
> > if (DIFF_OPT_TST(opt, FIND_COPIES_HARDER) ||
> > - hashcmp(t1->entry.sha1, t2->entry.sha1) ||
> > - (t1->entry.mode != t2->entry.mode))
> > - show_path(&base, opt, t1, t2);
> > + hashcmp(t1.entry.sha1, t2.entry.sha1) ||
> > + (t1.entry.mode != t2.entry.mode))
> > + show_path(&base, opt, &t1, &t2);
> >
> > - update_tree_entry(t1);
> > - update_tree_entry(t2);
> > + update_tree_entry(&t1);
> > + update_tree_entry(&t2);
> > }
> >
> > /* t1 < t2 */
> > else if (cmp < 0) {
> > - show_path(&base, opt, t1, /*t2=*/NULL);
> > - update_tree_entry(t1);
> > + show_path(&base, opt, &t1, /*t2=*/NULL);
> > + update_tree_entry(&t1);
> > }
> >
> > /* t1 > t2 */
> > else {
> > - show_path(&base, opt, /*t1=*/NULL, t2);
> > - update_tree_entry(t2);
> > + show_path(&base, opt, /*t1=*/NULL, &t2);
> > + update_tree_entry(&t2);
> > }
> > }
> >
> > strbuf_release(&base);
> > + free(t2tree);
> > + free(t1tree);
> > return 0;
> > }
> >
> > @@ -202,7 +209,7 @@ static inline int diff_might_be_rename(void)
> > !DIFF_FILE_VALID(diff_queued_diff.queue[0]->one);
> > }
> >
> > -static void try_to_follow_renames(struct tree_desc *t1, struct tree_desc
> > *t2, const char *base, struct diff_options *opt)
> > +static void try_to_follow_renames(const unsigned char *old, const unsigned
> > char *new, const char *base, struct diff_options *opt)
> > {
> > struct diff_options diff_opts;
> > struct diff_queue_struct *q = &diff_queued_diff;
> > @@ -240,7 +247,7 @@ static void try_to_follow_renames(struct tree_desc *t1,
> > struct tree_desc *t2, co
> > diff_opts.break_opt = opt->break_opt;
> > diff_opts.rename_score = opt->rename_score;
> > diff_setup_done(&diff_opts);
> > - diff_tree(t1, t2, base, &diff_opts);
> > + __diff_tree_sha1(old, new, base, &diff_opts);
> > diffcore_std(&diff_opts);
> > free_pathspec(&diff_opts.pathspec);
> >
> > @@ -301,23 +308,12 @@ static void try_to_follow_renames(struct tree_desc
> > *t1, struct tree_desc *t2, co
> >
> > int diff_tree_sha1(const unsigned char *old, const unsigned char *new,
> > const char *base, struct diff_options *opt)
> > {
> > - void *tree1, *tree2;
> > - struct tree_desc t1, t2;
> > - unsigned long size1, size2;
> > int retval;
> >
> > - tree1 = fill_tree_descriptor(&t1, old);
> > - tree2 = fill_tree_descriptor(&t2, new);
> > - size1 = t1.size;
> > - size2 = t2.size;
> > - retval = diff_tree(&t1, &t2, base, opt);
> > - if (!*base && DIFF_OPT_TST(opt, FOLLOW_RENAMES) &&
> > diff_might_be_rename()) {
> > - init_tree_desc(&t1, tree1, size1);
> > - init_tree_desc(&t2, tree2, size2);
> > - try_to_follow_renames(&t1, &t2, base, opt);
> > - }
> > - free(tree1);
> > - free(tree2);
> > + retval = __diff_tree_sha1(old, new, base, opt);
> > + if (!*base && DIFF_OPT_TST(opt, FOLLOW_RENAMES) &&
> > diff_might_be_rename())
> > + try_to_follow_renames(old, new, base, opt);
> > +
> > return retval;
> > }
--
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