From 7f01069131555a0e9ab332e578a9eb2815e1e12d Mon Sep 17 00:00:00 2001
From: Michael Vrable <vrable@cs.hmc.edu>
Date: Mon, 9 Jan 2012 21:30:02 -0800
Subject: [PATCH] Try out a fix for timeouts with limited bandwidth to cloud.

Delay writes for a short time (10 s) but not indefinitely.
---
 bluesky/bluesky-private.h |  2 ++
 bluesky/cache.c           | 34 ++++++++++++++++++++++++++++------
 bluesky/init.c            |  2 ++
 3 files changed, 32 insertions(+), 6 deletions(-)

diff --git a/bluesky/bluesky-private.h b/bluesky/bluesky-private.h
index 2595367..a783629 100644
--- a/bluesky/bluesky-private.h
+++ b/bluesky/bluesky-private.h
@@ -25,10 +25,12 @@ extern int bluesky_verbose;
 /* Target cache size levels. */
 extern int bluesky_watermark_low_dirty;
 extern int bluesky_watermark_medium_dirty;
+extern int bluesky_watermark_med2_dirty;
 extern int bluesky_watermark_high_dirty;
 
 extern int bluesky_watermark_low_total;
 extern int bluesky_watermark_medium_total;
+extern int bluesky_watermark_med2_total;
 extern int bluesky_watermark_high_total;
 
 /* TODO: Make this go away entirely. */
diff --git a/bluesky/cache.c b/bluesky/cache.c
index 8cd2fb3..cdd5c65 100644
--- a/bluesky/cache.c
+++ b/bluesky/cache.c
@@ -424,18 +424,19 @@ void bluesky_flushd_invoke(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
+ *   2 - should delay writers while memory frees up
+ *   3 - should block writers until memory frees up
  */
 static int compute_pressure(BlueSkyFS *fs)
 {
-    /* LEVEL 2 */
+    /* 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 (2)\n");
-        return 2;
+        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
@@ -446,8 +447,20 @@ static int compute_pressure(BlueSkyFS *fs)
     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) (2)\n",
+        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;
     }
 
@@ -489,10 +502,19 @@ void bluesky_flushd_invoke_conditional(BlueSkyFS *fs)
               g_atomic_int_get(&fs->cache_log_dirty));
         g_mutex_lock(fs->lock);
         pressure = compute_pressure(fs);
-        if (pressure > 1)
+        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 */
     }
 }
 
diff --git a/bluesky/init.c b/bluesky/init.c
index 70d9dad..e8c317a 100644
--- a/bluesky/init.c
+++ b/bluesky/init.c
@@ -34,10 +34,12 @@ int bluesky_max_threads = 16;
  */
 int bluesky_watermark_low_dirty    = (64 << 20) / BLUESKY_BLOCK_SIZE;
 int bluesky_watermark_medium_dirty = (96 << 20) / BLUESKY_BLOCK_SIZE;
+int bluesky_watermark_med2_dirty   = (160 << 20) / BLUESKY_BLOCK_SIZE;
 int bluesky_watermark_high_dirty   = (192 << 20) / BLUESKY_BLOCK_SIZE;
 
 int bluesky_watermark_low_total    = (64 << 20) / BLUESKY_BLOCK_SIZE;
 int bluesky_watermark_medium_total = (128 << 20) / BLUESKY_BLOCK_SIZE;
+int bluesky_watermark_med2_total   = (224 << 20) / BLUESKY_BLOCK_SIZE;
 int bluesky_watermark_high_total   = (256 << 20) / BLUESKY_BLOCK_SIZE;
 
 /* Environment variables that can be used to initialize settings. */
-- 
2.20.1