read-cache: log the number of scanned files to trace2

Report the number of files in the working directory that were read and
their hashes verified in `refresh_index()`.

FSMonitor improves the performance of commands like `git status` by
avoiding scanning the disk for changed files.  Let's measure this.

Signed-off-by: Jeff Hostetler <jeffhost@microsoft.com>
Reviewed-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/read-cache.c b/read-cache.c
index 893cc41e1d93eedae4ef7b4c9a84ac1a971d0a6f..c9dd7f4015ed9cc71ab064c7c90e662a9d518348 100644 (file)
--- a/read-cache.c
+++ b/read-cache.c
@@ -1365,7 +1365,8 @@ static struct cache_entry *refresh_cache_ent(struct index_state *istate,
                                             struct cache_entry *ce,
                                             unsigned int options, int *err,
                                             int *changed_ret,
-                                            int *t2_did_lstat)
+                                            int *t2_did_lstat,
+                                            int *t2_did_scan)
 {
        struct stat st;
        struct cache_entry *updated;
@@ -1445,6 +1446,8 @@ static struct cache_entry *refresh_cache_ent(struct index_state *istate,
                }
        }
 
+       if (t2_did_scan)
+               *t2_did_scan = 1;
        if (ie_modified(istate, ce, &st, options)) {
                if (err)
                        *err = EINVAL;
@@ -1523,6 +1526,7 @@ int refresh_index(struct index_state *istate, unsigned int flags,
        const char *unmerged_fmt;
        struct progress *progress = NULL;
        int t2_sum_lstat = 0;
+       int t2_sum_scan = 0;
 
        if (flags & REFRESH_PROGRESS && isatty(2))
                progress = start_delayed_progress(_("Refresh index"),
@@ -1547,6 +1551,7 @@ int refresh_index(struct index_state *istate, unsigned int flags,
                int changed = 0;
                int filtered = 0;
                int t2_did_lstat = 0;
+               int t2_did_scan = 0;
 
                ce = istate->cache[i];
                if (ignore_submodules && S_ISGITLINK(ce->ce_mode))
@@ -1574,8 +1579,9 @@ int refresh_index(struct index_state *istate, unsigned int flags,
 
                new_entry = refresh_cache_ent(istate, ce, options,
                                              &cache_errno, &changed,
-                                             &t2_did_lstat);
+                                             &t2_did_lstat, &t2_did_scan);
                t2_sum_lstat += t2_did_lstat;
+               t2_sum_scan += t2_did_scan;
                if (new_entry == ce)
                        continue;
                if (progress)
@@ -1612,6 +1618,7 @@ int refresh_index(struct index_state *istate, unsigned int flags,
                replace_index_entry(istate, i, new_entry);
        }
        trace2_data_intmax("index", NULL, "refresh/sum_lstat", t2_sum_lstat);
+       trace2_data_intmax("index", NULL, "refresh/sum_scan", t2_sum_scan);
        trace2_region_leave("index", "refresh", NULL);
        if (progress) {
                display_progress(progress, istate->cache_nr);
@@ -1625,7 +1632,7 @@ struct cache_entry *refresh_cache_entry(struct index_state *istate,
                                        struct cache_entry *ce,
                                        unsigned int options)
 {
-       return refresh_cache_ent(istate, ce, options, NULL, NULL, NULL);
+       return refresh_cache_ent(istate, ce, options, NULL, NULL, NULL, NULL);
 }