On 12/30/2020 2:42 PM, Elijah Newren wrote:
> On Wed, Dec 30, 2020 at 11:26 AM Derrick Stolee via GitGitGadget
> <gitgitgadget@xxxxxxxxx> wrote:
>>
>> From: Derrick Stolee <dstolee@xxxxxxxxxxxxx>
>>
>> The traverse_trees() method recusively walks through trees, but also
>
> recursively -- you're missing the second 'r'.
Thanks.
>> prunes the tree-walk based on a callback. Some callers, such as
>> unpack_trees(), are quite complicated and can have wildly different
>> performance between two different commands.
>
> Not sure it belongs in the commit message, but you do have me curious
> what you're digging in to...
I'm still testing whether my idea will work out. Hopefully soon. ;)
>> Create constants that count these values and then report the results at
>> the end of a process. These counts are cumulative across multiple "root"
>> instances of traverse_trees(), but they provide reproducible values for
>> demonstrating improvements to the pruning algorithm when possible.
>>
>> Signed-off-by: Derrick Stolee <dstolee@xxxxxxxxxxxxx>
>> ---
>> tree-walk.c | 33 +++++++++++++++++++++++++++++++++
>> unpack-trees.c | 1 -
>> 2 files changed, 33 insertions(+), 1 deletion(-)
>
> From the subject, you are changing tree-walk. unpack-trees depends on
> tree-walk, but why is something exposed to it with this kind of
> change? Maybe I'll see when I get to it.
Oops. I originally reported the stats at the end of unpack_trees(), but
it seems I didn't completely back out that change.
>> diff --git a/tree-walk.c b/tree-walk.c
>> index 0160294712b..2d6226d5f18 100644
>> --- a/tree-walk.c
>> +++ b/tree-walk.c
>> @@ -4,6 +4,7 @@
>> #include "object-store.h"
>> #include "tree.h"
>> #include "pathspec.h"
>> +#include "json-writer.h"
>>
>> static const char *get_mode(const char *str, unsigned int *modep)
>> {
>> @@ -167,6 +168,25 @@ int tree_entry_gently(struct tree_desc *desc, struct name_entry *entry)
>> return 1;
>> }
>>
>> +static int traverse_trees_atexit_registered;
>> +static int traverse_trees_count;
>> +static int traverse_trees_cur_depth;
>> +static int traverse_trees_max_depth;
>> +
>> +static void trace2_traverse_trees_statistics_atexit(void)
>> +{
>> + struct json_writer jw = JSON_WRITER_INIT;
>> +
>> + jw_object_begin(&jw, 0);
>> + jw_object_intmax(&jw, "traverse_trees_count", traverse_trees_count);
>> + jw_object_intmax(&jw, "traverse_trees_max_depth", traverse_trees_max_depth);
>> + jw_end(&jw);
>> +
>> + trace2_data_json("traverse_trees", the_repository, "statistics", &jw);
>> +
>> + jw_release(&jw);
>> +}
>
> Yeah, I don't know the json_writer or trace2 stuff; might be nice to
> cc Josh Steadmon or someone to review this patch. (Or perhaps he
> already reviewed internally?)
I guess I could have pointed out that this change is modeled after
a similar statistics reporting in 42e50e78 (revision.c: add trace2
stats around Bloom filter usage, 2020-04-06).
>> +
>> void setup_traverse_info(struct traverse_info *info, const char *base)
>> {
>> size_t pathlen = strlen(base);
>> @@ -180,6 +200,11 @@ void setup_traverse_info(struct traverse_info *info, const char *base)
>> info->namelen = pathlen;
>> if (pathlen)
>> info->prev = &dummy;
>> +
>> + if (trace2_is_enabled() && !traverse_trees_atexit_registered) {
>> + atexit(trace2_traverse_trees_statistics_atexit);
>> + traverse_trees_atexit_registered = 1;
>> + }
>> }
>>
>> char *make_traverse_path(char *path, size_t pathlen,
>> @@ -416,6 +441,12 @@ int traverse_trees(struct index_state *istate,
>> int interesting = 1;
>> char *traverse_path;
>>
>> + traverse_trees_count++;
>> + traverse_trees_cur_depth++;
>> +
>> + if (traverse_trees_cur_depth > traverse_trees_max_depth)
>> + traverse_trees_max_depth = traverse_trees_cur_depth;
>> +
>> if (n >= ARRAY_SIZE(entry))
>> BUG("traverse_trees() called with too many trees (%d)", n);
>>
>> @@ -515,6 +546,8 @@ int traverse_trees(struct index_state *istate,
>> free(traverse_path);
>> info->traverse_path = NULL;
>> strbuf_release(&base);
>> +
>> + traverse_trees_cur_depth--;
>
> I double-checked to see if there were any other return sites in this
> function. There aren't, which is nice and keeps this clean.
>
>> return error;
>> }
>>
>> diff --git a/unpack-trees.c b/unpack-trees.c
>> index 323280dd48b..02f484604ac 100644
>> --- a/unpack-trees.c
>> +++ b/unpack-trees.c
>> @@ -1559,7 +1559,6 @@ static void populate_from_existing_patterns(struct unpack_trees_options *o,
>> free(sparse);
>> }
>>
>> -
>
> Did you mean to combine this cleanup with some other patch? If not,
> could it be put into its own patch?
It should be dropped! Thanks.
>> static int verify_absent(const struct cache_entry *,
>> enum unpack_trees_error_types,
>> struct unpack_trees_options *);
>> --
>> gitgitgadget
>
> Seems like a good change other than a few small nits. I don't know
> the json_writer/trace2 stuff, so you might want another reviewer, but
> it's only a few lines and seems relatively straightforward.
I should point out that an easy way to test this locally is
to run
GIT_TRACE2_PERF=1 git read-tree -mu HEAD
to trigger a full recursive walk. The output JSON payload looks
like this:
statistics:{"traverse_trees_count":203,"traverse_trees_max_depth":7}
Thanks,
-Stolee
