[Qemu-devel] [PATCH v6 17/47] ram_debug_dump_bitmap: Dump a migration bitmap as text

["Dr. David Alan Gilbert (git)" <dgilbert@redhat.com>]

From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>

Misses out lines that are all the expected value so the output
can be quite compact depending on the circumstance.

Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
---
 arch_init.c                   | 40 +++++++++++++++++++++++++++++++++++++++-
 include/migration/migration.h |  1 +
 2 files changed, 40 insertions(+), 1 deletion(-)

diff --git a/arch_init.c b/arch_init.c
index 3a21f0e..2b0cd18 100644
--- a/arch_init.c
+++ b/arch_init.c
@@ -833,13 +833,51 @@ static void reset_ram_globals(void)
 
 #define MAX_WAIT 50 /* ms, half buffered_file limit */
 
-
 /* Each of ram_save_setup, ram_save_iterate and ram_save_complete has
  * long-running RCU critical section.  When rcu-reclaims in the code
  * start to become numerous it will be necessary to reduce the
  * granularity of these critical sections.
  */
 
+/*
+ * 'expected' is the value you expect the bitmap mostly to be full
+ * of and it won't bother printing lines that are all this value
+ * if 'todump' is null the migration bitmap is dumped.
+ */
+void ram_debug_dump_bitmap(unsigned long *todump, bool expected)
+{
+    int64_t ram_pages = last_ram_offset() >> TARGET_PAGE_BITS;
+
+    int64_t cur;
+    int64_t linelen = 128;
+    char linebuf[129];
+
+    if (!todump) {
+        todump = migration_bitmap;
+    }
+
+    for (cur = 0; cur < ram_pages; cur += linelen) {
+        int64_t curb;
+        bool found = false;
+        /*
+         * Last line; catch the case where the line length
+         * is longer than remaining ram
+         */
+        if (cur+linelen > ram_pages) {
+            linelen = ram_pages - cur;
+        }
+        for (curb = 0; curb < linelen; curb++) {
+            bool thisbit = test_bit(cur+curb, todump);
+            linebuf[curb] = thisbit ? '1' : '.';
+            found = found || (thisbit != expected);
+        }
+        if (found) {
+            linebuf[curb] = '\0';
+            fprintf(stderr,  "0x%08" PRIx64 " : %s\n", cur, linebuf);
+        }
+    }
+}
+
 static int ram_save_setup(QEMUFile *f, void *opaque)
 {
     RAMBlock *block;
diff --git a/include/migration/migration.h b/include/migration/migration.h
index 0719d82..fb7551d 100644
--- a/include/migration/migration.h
+++ b/include/migration/migration.h
@@ -152,6 +152,7 @@ uint64_t xbzrle_mig_pages_cache_miss(void);
 double xbzrle_mig_cache_miss_rate(void);
 
 void ram_handle_compressed(void *host, uint8_t ch, uint64_t size);
+void ram_debug_dump_bitmap(unsigned long *todump, bool expected);
 
 /**
  * @migrate_add_blocker - prevent migration from proceeding
-- 
2.1.0