g_thread_create((GThreadFunc)flushd_task, fs, FALSE, NULL);
}
+/* 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 delay writers while memory frees up
+ * 3 - should block writers until memory frees up
+ */
+static int compute_pressure(BlueSkyFS *fs)
+{
+ /* LEVEL 3 */
+ /* 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)
+ {
+ g_print("pressure: too much dirty data (3)\n");
+ return 3;
+ }
+
+ /* 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("pressure: too many dirty journals (%d >= %d) (3)\n",
+ dirty_journals, dirty_limit);
+ return 3;
+ }
+
+ /* LEVEL 2 */
+ if (g_atomic_int_get(&fs->cache_dirty) > bluesky_watermark_med2_dirty) {
+ g_print("pressure: too much dirty data (2)\n");
+ return 2;
+ }
+
+ if (dirty_journals > 1 && dirty_journals > dirty_limit * 3 / 4) {
+ printf("pressure: many dirty journals (%d), should start writeback (2)\n",
+ dirty_journals);
+ return 2;
+ }
+
+ /* LEVEL 1 */
+ if (g_atomic_int_get(&fs->cache_dirty) > bluesky_watermark_medium_dirty) {
+ g_print("pressure: too much dirty data (1)\n");
+ return 1;
+ }
+
+ if (dirty_journals > 1 && dirty_journals > dirty_limit / 2) {
+ printf("pressure: many dirty journals (%d), should start writeback (1)\n",
+ dirty_journals);
+ return 1;
+ }
+
+ return 0;
+}
+
void bluesky_flushd_invoke_conditional(BlueSkyFS *fs)
{
- if (g_atomic_int_get(&fs->cache_dirty) < bluesky_watermark_medium_dirty)
+ int pressure = compute_pressure(fs);
+ if (pressure == 0)
return;
if (bluesky_verbose) {
/* 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 > 2) {
+ g_cond_wait(fs->flushd_cond, fs->lock);
+ } else if (pressure > 1) {
+ /* Wait for up to 10 seconds. */
+ GTimeVal timeout;
+ g_get_current_time(&timeout);
+ g_time_val_add(&timeout, 10 * 1000 * 1000);
+ g_cond_timed_wait(fs->flushd_cond, fs->lock, &timeout);
+ }
g_mutex_unlock(fs->lock);
+ pressure = compute_pressure(fs);
+ if (pressure == 1)
+ break; /* Do not loop indefinitely for a pressure of 1 */
}
}