mem: optimize debug logging enqueued pages

During restore, CRIU prints "Enqueue page-read" messages for
each page-read request [1]. However, this message does not
provide useful information, increases performance overhead
during restore and the size of log file.

$ ./zdtm.py run -t zdtm/static/maps06 -f h -k always
$ grep 'Enqueue' dump/zdtm/static/maps06/56/1/restore.log | wc -l
20494

This commit replaces these log messages with a single message
that shows the number of enqueued page-read requests.

$ grep 'enqueued' dump/zdtm/static/maps06/56/1/restore.log
(00.061449)     56: nr_enqueued_pages:   20493

[1] 91388fc

Signed-off-by: Radostin Stoyanov <rstoyanov@fedoraproject.org>

criu/mem.c

@@ -1087,6 +1087,7 @@ static int restore_priv_vma_content(struct pstree_item *t, struct page_read *pr)
 	unsigned int nr_shared = 0;
 	unsigned int nr_dropped = 0;
 	unsigned int nr_compared = 0;
+	unsigned int nr_enqueued = 0;
 	unsigned int nr_lazy = 0;
 	unsigned long va;
 
@@ -1162,7 +1163,8 @@ static int restore_priv_vma_content(struct pstree_item *t, struct page_read *pr)
 				len >>= PAGE_SHIFT;
 				nr_restored += len;
 				i += len - 1;
-				pr_debug("Enqueue page-read\n");
+
+				nr_enqueued++;
 				continue;
 			}
 
@@ -1257,6 +1259,7 @@ static int restore_priv_vma_content(struct pstree_item *t, struct page_read *pr)
 	cnt_add(CNT_PAGES_RESTORED, nr_restored);
 
 	pr_info("nr_restored_pages: %d\n", nr_restored);
+	pr_info("nr_enqueued_pages:   %d\n", nr_enqueued);
 	pr_info("nr_shared_pages:   %d\n", nr_shared);
 	pr_info("nr_dropped_pages:   %d\n", nr_dropped);
 	pr_info("nr_lazy:           %d\n", nr_lazy);