[RFC PATCH v6 31/34] dyndbg: detect repeated site recs in add_module

[Jim Cromie]

Since the 1st patch in this series, which partitioned into structs
_ddebug & _ddebug_site while leaving lineno in _ddebug, we have had
chunks of repeating site records; every pr_debug in a function
has identical site data.

To avoid reliance on the redundant data, we need:
0. ._map field (added HEAD~1)
1. detection of repeating sites.

In ddebug_add_module(), alter the index initialization loop to recognize
the 1st record in each block of repeats, remember it in "j", and use it
to ._map all the pr_debugs in that block.  To find the block starts,
we can just look for a new .function in each row.

This gives us, for each function; 1st used row, 2nd-Nth unused rows.
To actually reclaim useful memory chunks, we will have to pack the
site records up towards the header.

Heres what booting with dynamic_debug.verbose=3 will show:

1st 3 builtin modules:
- cols 3,4 row 1 - shows +1 due to previous head64
- cols 2,4 - shows repeat detection working

rcu: Hierarchical SRCU implementation.
dyndbg: add-module: head64.1 sites
dyndbg:  skip header head64
dyndbg: add-module: main.6 sites
Callback from call_rcu_tasks_trace() invoked.
dyndbg:  0 0 1 1 main.run_init_process.1358
dyndbg:  1 0 2 1 main.run_init_process.1356
dyndbg:  2 0 3 1 main.run_init_process.1355
dyndbg:  3 0 4 1 main.run_init_process.1353
dyndbg:  4 4 5 5 main.initcall_blacklisted.1142
dyndbg:  5 5 6 6 main.initcall_blacklist.1103
dyndbg:   6 debug prints in module main (in 3 functions)
dyndbg: add-module: initramfs.1 sites
dyndbg:  0 0 7 7 initramfs.unpack_to_rootfs.496
dyndbg:   1 debug prints in module initramfs (in 1 functions)
dyndbg: add-module: ibs.3 sites
dyndbg:  0 0 8 8 ibs.force_ibs_eilvt_setup.926
dyndbg:  1 1 9 9 ibs.setup_ibs_ctl.897
dyndbg:  2 1 10 9 ibs.setup_ibs_ctl.890
dyndbg:   3 debug prints in module ibs (in 2 functions)

for a loaded module:
- row 0000 - is the header (function==module) - lineno is garbage
- cols 2,4 - show repeat detect
- 9 functions - over by 1, due to counting the header

dyndbg: add-module: intel_rapl_common.13 sites
dyndbg:  0 0 0 0 intel_rapl_common.intel_rapl_common.16928
dyndbg:  1 1 1 1 intel_rapl_common.rapl_remove_package.1279
dyndbg:  2 2 2 2 intel_rapl_common.rapl_detect_domains.1245
dyndbg:  3 2 3 2 intel_rapl_common.rapl_detect_domains.1242
dyndbg:  4 4 4 4 intel_rapl_common.rapl_package_register_powercap.1159
dyndbg:  5 4 5 4 intel_rapl_common.rapl_package_register_powercap.1145
dyndbg:  6 4 6 4 intel_rapl_common.rapl_package_register_powercap.1114
dyndbg:  7 4 7 4 intel_rapl_common.rapl_package_register_powercap.1108
dyndbg:  8 8 8 8 intel_rapl_common.rapl_update_domain_data.1083
dyndbg:  9 9 9 9 intel_rapl_common.rapl_check_unit_atom.824
dyndbg:  10 10 10 10 intel_rapl_common.rapl_check_unit_core.796
dyndbg:  11 11 11 11 intel_rapl_common.rapl_read_data_raw.722
dyndbg:  12 12 12 12 intel_rapl_common.contraint_to_pl.303
dyndbg:  13 debug prints in module intel_rapl_common (in 9 functions)
Signed-off-by: Jim Cromie <jim.cromie@xxxxxxxxx>
---
 lib/dynamic_debug.c | 26 ++++++++++++++++++++------
 1 file changed, 20 insertions(+), 6 deletions(-)

diff --git a/lib/dynamic_debug.c b/lib/dynamic_debug.c
index 524303a04462..e12538640b51 100644
--- a/lib/dynamic_debug.c
+++ b/lib/dynamic_debug.c
@@ -1073,7 +1073,7 @@ static int __ddebug_add_module(struct _ddebug *tab, struct _ddebug_site *sites,
 {
 	struct ddebug_table *dt;
 	union _ddebug_header *dh = (union _ddebug_header *) &tab[0];
-	int i;
+	int i, j, ct;
 
 	v3pr_info("add-module: %s.%d sites\n", modname, numdbgs);
 
@@ -1107,10 +1107,22 @@ static int __ddebug_add_module(struct _ddebug *tab, struct _ddebug_site *sites,
 	dt->ddebugs = tab;
 	dt->sites = sites;
 
-	for (i = 0; i < numdbgs; i++) {
-		tab[i]._back = base + i;
-		tab[i]._map = base + i;
-		v3pr_info(" %d %d %d %s.%s.%d\n", i, tab[i]._back, tab[i]._map,
+	/*
+	 * Since sites don't have lineno (thats in struct _ddebug),
+	 * all pr_debugs in a function have identical site data.  So
+	 * we watch for repeats on site.function, and reuse the index
+	 * of the 1st site record in a repeating block.
+	 */
+	for (ct = i = j = 0; i < numdbgs; i++) {
+		tab[i]._back = base + i; /* index back to header */
+
+		if (sites[i].function != sites[j].function) {
+			j = i; /* remember 1st row with new fn */
+			ct++;
+		}
+		tab[i]._map = base + j;
+
+		v3pr_info(" %d %d %d %d %s.%s.%d\n", i, j, tab[i]._back, tab[i]._map,
 			  modname, sites[i].function, tab[i].lineno);
 	}
 
@@ -1118,7 +1130,9 @@ static int __ddebug_add_module(struct _ddebug *tab, struct _ddebug_site *sites,
 	list_add(&dt->link, &ddebug_tables);
 	mutex_unlock(&ddebug_lock);
 
-	v2pr_info("%3u debug prints in module %s\n", numdbgs, modname);
+	v2pr_info("%3u debug prints in module %s (in %d functions)\n",
+		  numdbgs, modname, ++ct);
+
 	return 0;
 }
 
-- 
2.31.1