Add write throttling based on the size of the uncommitted journal

[bluesky.git] / bluesky / cache.c

diff --git a/bluesky/cache.c b/bluesky/cache.c
index bfbfe3c..b20960c 100644 (file)
--- a/bluesky/cache.c
+++ b/bluesky/cache.c
@@ -328,12 +328,14 @@ void bluesky_cachefile_gc(BlueSkyFS *fs)
          * then we'll just skip the file on this pass. */
         if (g_mutex_trylock(cachefile->lock)) {
             int64_t age = bluesky_get_current_time() - cachefile->atime;
-            g_print("%s addr=%p mapcount=%d refcount=%d atime_age=%f",
-                    cachefile->filename, cachefile->addr, cachefile->mapcount,
-                    cachefile->refcount, age / 1e6);
-            if (cachefile->fetching)
-                g_print(" (fetching)");
-            g_print("\n");
+            if (bluesky_verbose) {
+                g_print("%s addr=%p mapcount=%d refcount=%d size=%d atime_age=%f",
+                        cachefile->filename, cachefile->addr, cachefile->mapcount,
+                        cachefile->refcount, cachefile->disk_used, age / 1e6);
+                if (cachefile->fetching)
+                    g_print(" (fetching)");
+                g_print("\n");
+            }
 
             gboolean deletion_candidate = FALSE;
             if (g_atomic_int_get(&fs->log->disk_used)
@@ -353,14 +355,19 @@ void bluesky_cachefile_gc(BlueSkyFS *fs)
             }
 
             if (deletion_candidate) {
-                g_print("   ...deleting\n");
+                if (bluesky_verbose) {
+                    g_print("   ...deleting\n");
+                }
                 if (unlinkat(fs->log->dirfd, cachefile->filename, 0) < 0) {
                     fprintf(stderr, "Unable to unlink journal %s: %m\n",
                             cachefile->filename);
                 }
 
-                g_atomic_int_add(&fs->log->disk_used, -(cachefile->len / 1024));
+                g_atomic_int_add(&fs->log->disk_used, -cachefile->disk_used);
                 g_hash_table_remove(fs->log->mmap_cache, cachefile->filename);
+                bluesky_rangeset_free(cachefile->items);
+                if (cachefile->prefetches != NULL)
+                    bluesky_rangeset_free(cachefile->prefetches);
                 g_mutex_unlock(cachefile->lock);
                 g_mutex_free(cachefile->lock);
                 g_cond_free(cachefile->cond);
@@ -414,9 +421,50 @@ void bluesky_flushd_invoke(BlueSkyFS *fs)
     g_thread_create((GThreadFunc)flushd_task, fs, FALSE, NULL);
 }
 
-void bluesky_flushd_invoke_conditional(BlueSkyFS *fs)
+/* How urgent is flushing out data?  Returns one of several values:
+ *   0 - memory state is fine
+ *   1 - should launch flushd if not already running
+ *   2 - should block writers until memory frees up
+ */
+static int compute_pressure(BlueSkyFS *fs)
 {
+    /* LEVEL 2 */
+    /* Too much dirty data in memory? */
+    if (g_atomic_int_get(&fs->cache_dirty)
+                + g_atomic_int_get(&fs->cache_log_dirty)
+           > bluesky_watermark_high_dirty)
+        return 2;
+
+    /* Too much uncommitted data in the journal on disk, not yet flushed to the
+     * cloud? */
+    printf("Dirty journals: %d to %d\n",
+           fs->log->journal_watermark, fs->log->seq_num);
+    int dirty_limit;
+    dirty_limit = bluesky_options.cache_size / (LOG_SEGMENT_SIZE / 1024) / 2;
+    int dirty_journals = fs->log->seq_num - fs->log->journal_watermark + 1;
+    if (dirty_journals > 1 && dirty_journals >= dirty_limit) {
+        printf("Too many dirty journals (%d >= %d)\n",
+               dirty_journals, dirty_limit);
+        return 2;
+    }
+
+    /* LEVEL 1 */
     if (g_atomic_int_get(&fs->cache_dirty) < bluesky_watermark_medium_dirty)
+        return 1;
+
+    if (dirty_journals > 1 && dirty_journals > dirty_limit / 2) {
+        printf("Many dirty journals (%d), should start writeback\n",
+               dirty_journals);
+        return 1;
+    }
+
+    return 0;
+}
+
+void bluesky_flushd_invoke_conditional(BlueSkyFS *fs)
+{
+    int pressure = compute_pressure(fs);
+    if (pressure == 0)
         return;
 
     if (bluesky_verbose) {
@@ -429,16 +477,17 @@ void bluesky_flushd_invoke_conditional(BlueSkyFS *fs)
 
     /* If the system is under heavy memory pressure, actually delay execution
      * so the flush daemon can catch up. */
-    while (g_atomic_int_get(&fs->cache_dirty)
-                + g_atomic_int_get(&fs->cache_log_dirty)
-           > bluesky_watermark_high_dirty) {
+    while (pressure > 1) {
         g_log("bluesky/flushd", G_LOG_LEVEL_DEBUG,
               "Waiting due to memory pressure, dirty=%d + %d",
               g_atomic_int_get(&fs->cache_dirty),
               g_atomic_int_get(&fs->cache_log_dirty));
         g_mutex_lock(fs->lock);
-        g_cond_wait(fs->flushd_cond, fs->lock);
+        pressure = compute_pressure(fs);
+        if (pressure > 1)
+            g_cond_wait(fs->flushd_cond, fs->lock);
         g_mutex_unlock(fs->lock);
+        pressure = compute_pressure(fs);
     }
 }