Re: [PATCH v4 2/5] unpack-trees: add performance tracing

[Ben Peart]

On 8/12/2018 4:15 AM, Nguyễn Thái Ngọc Duy wrote:
We're going to optimize unpack_trees() a bit in the following
patches. Let's add some tracing to measure how long it takes before
and after. This is the baseline ("git checkout -" on webkit.git, 275k
files on worktree)

     performance: 0.056651714 s:  read cache .git/index
     performance: 0.183101080 s:  preload index
     performance: 0.008584433 s:  refresh index
     performance: 0.633767589 s:   traverse_trees
     performance: 0.340265448 s:   check_updates
     performance: 0.381884638 s:   cache_tree_update
     performance: 1.401562947 s:  unpack_trees
     performance: 0.338687914 s:  write index, changed mask = 2e
     performance: 0.411927922 s:    traverse_trees
     performance: 0.000023335 s:    check_updates
     performance: 0.423697246 s:   unpack_trees
     performance: 0.423708360 s:  diff-index
     performance: 2.559524127 s: git command: git checkout -

Signed-off-by: Nguyễn Thái Ngọc Duy <pclo...@gmail.com>
---
  cache-tree.c   | 2 ++
  unpack-trees.c | 9 ++++++++-
  2 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/cache-tree.c b/cache-tree.c
index 6b46711996..105f13806f 100644
--- a/cache-tree.c
+++ b/cache-tree.c
@@ -433,7 +433,9 @@ int cache_tree_update(struct index_state *istate, int flags)
  
  	if (i)
                return i;
+       trace_performance_enter();

This one is a little odd to me.  I think the either the 
trace_performance_enter() call should move up to include the 
verify_cache() call or the enter/leave should move into the update_one() 
call as that is all it is measuring/reporting on.

        i = update_one(it, cache, entries, "", 0, &skip, flags);
+       trace_performance_leave("cache_tree_update");
        if (i < 0)
                return i;
        istate->cache_changed |= CACHE_TREE_CHANGED;
diff --git a/unpack-trees.c b/unpack-trees.c
index cd0680f11e..b237eaa0f2 100644
--- a/unpack-trees.c
+++ b/unpack-trees.c
@@ -354,6 +354,7 @@ static int check_updates(struct unpack_trees_options *o)
        struct checkout state = CHECKOUT_INIT;
        int i;
  
+	trace_performance_enter();
        state.force = 1;
        state.quiet = 1;
        state.refresh_cache = 1;
@@ -423,6 +424,7 @@ static int check_updates(struct unpack_trees_options *o)
        errs |= finish_delayed_checkout(&state);
        if (o->update)
                git_attr_set_direction(GIT_ATTR_CHECKIN, NULL);
+       trace_performance_leave("check_updates");
        return errs != 0;
  }
  
@@ -1279,6 +1281,7 @@ int unpack_trees(unsigned len, struct tree_desc *t, struct unpack_trees_options
        if (len > MAX_UNPACK_TREES)
                die("unpack_trees takes at most %d trees", MAX_UNPACK_TREES);
  
+	trace_performance_enter();
        memset(&el, 0, sizeof(el));
        if (!core_apply_sparse_checkout || !o->update)
                o->skip_sparse_checkout = 1;
@@ -1351,7 +1354,10 @@ int unpack_trees(unsigned len, struct tree_desc *t, 
struct unpack_trees_options
                        }
                }
  
-		if (traverse_trees(len, t, &info) < 0)
+               trace_performance_enter();
+               ret = traverse_trees(len, t, &info);
+               trace_performance_leave("traverse_trees");

Why not move this enter/leave pair into the traverse_trees() function 
itself?

+               if (ret < 0)
                        goto return_failed;
        }
  
@@ -1443,6 +1449,7 @@ int unpack_trees(unsigned len, struct tree_desc *t, struct unpack_trees_options
        o->src_index = NULL;
  
  done:
+       trace_performance_leave("unpack_trees");
        clear_exclude_list(&el);
        return ret;