[Qemu-devel] [PATCH v7 07/42] ram_debug_dump_bitmap: Dump a migration bitmap as text

[Dr. David Alan Gilbert (git)]

From: "Dr. David Alan Gilbert" <address@hidden>

Useful for debugging the migration bitmap and other bitmaps
of the same format (including the sentmap in postcopy).

The bitmap is printed to stderr.
Lines that are all the expected value are excluded so the output
can be quite compact for many bitmaps.

Signed-off-by: Dr. David Alan Gilbert <address@hidden>
---
 include/migration/migration.h |  1 +
 migration/ram.c               | 38 ++++++++++++++++++++++++++++++++++++++
 2 files changed, 39 insertions(+)

diff --git a/include/migration/migration.h b/include/migration/migration.h
index 9387c8c..b3a7f75 100644
--- a/include/migration/migration.h
+++ b/include/migration/migration.h
@@ -144,6 +144,7 @@ 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
diff --git a/migration/ram.c b/migration/ram.c
index 57368e1..efc215a 100644
--- a/migration/ram.c
+++ b/migration/ram.c
@@ -1051,6 +1051,44 @@ static void reset_ram_globals(void)
 
 #define MAX_WAIT 50 /* ms, half buffered_file limit */
 
+/*
+ * 'expected' is the value you expect the bitmap mostly to be full
+ * of; 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);
+        }
+    }
+}
 
 /* Each of ram_save_setup, ram_save_iterate and ram_save_complete has
  * long-running RCU critical section.  When rcu-reclaims in the code
-- 
2.4.3