[PATCH makedumpfile v2 4/9] Introduce a stat for pages retained by extension

[Stephen Brennan]

Extensions can mark pages to be excluded, but those pages may already be
excluded due to the dump level. We have a statistic to count pages
excluded by extensions. It counts only pages which were excluded because
no other criteria excluded them.

Extensions can mark pages to be retained, but there is no statistic to
count them. Adding a counter to the code as-is would not give us the
value that we care about. Just as above, pages marked for inclusion may
have been included anyway due to the dump-level configuration. The most
useful statistic is the one that tells us how many pages were included
by the extension, which would not have been included otherwise.

Introduce a statistic that counts this amount.  To do so, we have to
skip the short-circuit evaluation when PG_INCLUDE is returned. This
seems like a worthwhile trade-off, since the dump-level checks are all
reasonably efficient.

Signed-off-by: Stephen Brennan <stephen.s.brennan at oracle.com>
---
 makedumpfile.c | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/makedumpfile.c b/makedumpfile.c
index e3a4a6f..fca42e1 100644
--- a/makedumpfile.c
+++ b/makedumpfile.c
@@ -106,6 +106,7 @@ mdf_pfn_t pfn_elf_excluded;
 mdf_pfn_t pfn_extension;
 
 mdf_pfn_t num_dumped;
+mdf_pfn_t num_extension_retained;
 
 int retcd = FAILED;	/* return code */
 
@@ -6638,8 +6639,6 @@ check_order:
 		 * makedumpfile extensions
 		 */
 		filter_pg = run_extension_callback(pfn, pcache, &i);
-		if (filter_pg == PG_INCLUDE)
-			continue;
 
 		/*
 		 * Exclude the free page managed by a buddy
@@ -6721,6 +6720,13 @@ check_order:
 		else
 			continue;
 
+		if (filter_pg == PG_INCLUDE) {
+			/* Account pages which would have been excluded, but were
+			 * retained by an extension. */
+			num_extension_retained += nr_pages;
+			continue;
+		}
+
 		/*
 		 * Execute exclusion
 		 */
@@ -8264,6 +8270,7 @@ write_elf_pages_cyclic(struct cache_data *cd_header, struct cache_data *cd_page)
 	if (info->flag_cyclic) {
 		pfn_zero = pfn_cache = pfn_cache_private = 0;
 		pfn_user = pfn_free = pfn_hwpoison = pfn_offline = pfn_extension = 0;
+		num_extension_retained = 0;
 		pfn_memhole = info->max_mapnr;
 	}
 
@@ -9609,6 +9616,7 @@ write_kdump_pages_and_bitmap_cyclic(struct cache_data *cd_header, struct cache_d
 		 */
 		pfn_zero = pfn_cache = pfn_cache_private = 0;
 		pfn_user = pfn_free = pfn_hwpoison = pfn_offline = pfn_extension = 0;
+		num_extension_retained = 0;
 		pfn_memhole = info->max_mapnr;
 
 		/*
@@ -10576,6 +10584,7 @@ print_report(void)
 	REPORT_MSG("    Extension filter pages  : 0x%016llx\n", pfn_extension);
 	REPORT_MSG("  Remaining pages  : 0x%016llx\n",
 	    pfn_original - pfn_excluded);
+	REPORT_MSG("    Extension retain pages  : 0x%016llx\n", num_extension_retained);
 
 	if (info->flag_elf_dumpfile) {
 		REPORT_MSG("     in ELF format : 0x%016llx\n",
-- 
2.52.0