#include "bluesky-private.h"
#define WRITEBACK_DELAY (20 * 1000000)
+#define CACHE_DROP_DELAY (20 * 1000000)
/* Filesystem caching and cache coherency. There are actually a couple of
* different tasks that are performed here:
* - Writing batches of data to the cloud.
*/
-static void writeback_complete(gpointer a, gpointer i)
-{
- BlueSkyInode *inode = (BlueSkyInode *)i;
-
- if (bluesky_verbose) {
- g_log("bluesky/flushd", G_LOG_LEVEL_DEBUG,
- "Writeback for inode %"PRIu64" complete", inode->inum);
- }
-
- g_mutex_lock(inode->lock);
-
- inode->change_commit = inode->change_pending;
- inode->change_pending = 0;
- if (inode->change_count == inode->change_commit) {
- /* If inode is no longer dirty... */
- inode->change_time = 0;
- g_mutex_lock(inode->fs->lock);
- bluesky_list_unlink(&inode->fs->dirty_list, inode->dirty_list);
- inode->dirty_list = NULL;
- g_mutex_unlock(inode->fs->lock);
- }
-
- g_mutex_unlock(inode->lock);
-}
-
static void flushd_dirty_inode(BlueSkyInode *inode)
{
BlueSkyFS *fs = inode->fs;
g_mutex_lock(fs->lock);
- bluesky_list_unlink(&fs->dirty_list, inode->dirty_list);
- inode->dirty_list = NULL;
+ bluesky_list_unlink(&fs->unlogged_list, inode->unlogged_list);
+ inode->unlogged_list = NULL;
g_mutex_unlock(fs->lock);
/* Inode is clean; nothing to do. */
if (inode->change_count == inode->change_commit)
return;
- /* Inode writeback is in progress; put back on the dirty list. */
- if (inode->change_pending) {
- /* Waiting for an earlier writeback to finish, so don't start a new
- * writeback yet. */
- g_mutex_lock(fs->lock);
- inode->change_time = bluesky_get_current_time();
- bluesky_list_unlink(&fs->dirty_list, inode->dirty_list);
- inode->dirty_list = bluesky_list_prepend(&fs->dirty_list, inode);
- g_mutex_unlock(fs->lock);
- return;
- }
-
if (bluesky_verbose) {
g_log("bluesky/flushd", G_LOG_LEVEL_DEBUG,
"Starting flush of inode %"PRIu64, inode->inum);
}
- inode->change_pending = inode->change_count;
bluesky_inode_start_sync(inode);
}
+/* Check whether memory usage may have dropped below critical thresholds for
+ * waking up waiting threads. */
+void flushd_check_wakeup(BlueSkyFS *fs)
+{
+ int dirty = g_atomic_int_get(&fs->cache_dirty);
+ dirty += g_atomic_int_get(&fs->cache_log_dirty);
+
+ if (dirty <= bluesky_watermark_high_dirty)
+ g_cond_broadcast(fs->flushd_cond);
+}
+
/* Try to flush dirty data to disk, either due to memory pressure or due to
* timeouts. */
static void flushd_dirty(BlueSkyFS *fs)
int64_t start_time = bluesky_get_current_time();
g_mutex_lock(fs->lock);
+ while (1) {
+ BlueSkyInode *inode;
+ if (fs->unlogged_list.prev == NULL)
+ break;
+ inode = fs->unlogged_list.prev->data;
+
+ if (bluesky_verbose) {
+ g_log("bluesky/flushd", G_LOG_LEVEL_DEBUG,
+ "Considering flushing inode %"PRIu64, inode->inum);
+ }
+
+ /* Stop processing dirty inodes if we both have enough memory available
+ * and the oldest inode is sufficiently new that it need not be flushed
+ * out. */
+ uint64_t elapsed = bluesky_get_current_time() - inode->change_time;
+ if (g_atomic_int_get(&fs->cache_dirty) < bluesky_watermark_low_dirty
+ && elapsed < WRITEBACK_DELAY)
+ break;
+ if (inode->change_time > start_time)
+ break;
+
+ bluesky_inode_ref(inode);
+
+ g_mutex_unlock(fs->lock);
+
+ g_mutex_lock(inode->lock);
+ flushd_dirty_inode(inode);
+ g_mutex_unlock(inode->lock);
+ bluesky_inode_unref(inode);
+
+ g_mutex_lock(fs->lock);
+ flushd_check_wakeup(fs);
+ }
+
+ g_cond_broadcast(fs->flushd_cond);
+
+ g_mutex_unlock(fs->lock);
+}
+
+/* Try to flush dirty data to the cloud.
+ * TODO: Rewrite this to work on cloud log items rather than inodes, so we can
+ * better track which logs are fully synchronized to the cloud and can be
+ * garbage collected if needed? */
+static void flushd_cloud(BlueSkyFS *fs)
+{
+ int64_t start_time = bluesky_get_current_time();
+ g_mutex_lock(fs->lock);
+
while (1) {
BlueSkyInode *inode;
if (fs->dirty_list.prev == NULL)
if (bluesky_verbose) {
g_log("bluesky/flushd", G_LOG_LEVEL_DEBUG,
- "Considering flushing inode %"PRIu64, inode->inum);
+ "Flushing inode %"PRIu64" to cloud", inode->inum);
}
/* Stop processing dirty inodes if we both have enough memory available
g_mutex_lock(inode->lock);
flushd_dirty_inode(inode);
+ g_mutex_lock(fs->lock);
+ bluesky_list_unlink(&fs->dirty_list, inode->dirty_list);
+ inode->dirty_list = NULL;
+ g_mutex_unlock(fs->lock);
+
+ BlueSkyCloudLog *log = inode->committed_item;
+ bluesky_cloudlog_ref(log);
g_mutex_unlock(inode->lock);
+
+ if (log != NULL)
+ bluesky_cloudlog_serialize(log, fs);
bluesky_inode_unref(inode);
+ bluesky_cloudlog_unref(log);
g_mutex_lock(fs->lock);
}
g_mutex_unlock(fs->lock);
+ bluesky_cloudlog_flush(fs);
}
/* Drop cached data for a given inode, if it is clean. inode must be locked. */
{
if (inode->type == BLUESKY_REGULAR)
bluesky_file_drop_cached(inode);
+
+ BlueSkyCloudLog *log = inode->committed_item;
+ if (log != NULL) {
+ g_mutex_lock(log->lock);
+ if (log->data != NULL
+ && g_atomic_int_get(&log->data_lock_count) == 0
+ && (log->location_flags != 0))
+ {
+ bluesky_cloudlog_stats_update(log, -1);
+ bluesky_string_unref(log->data);
+ log->data = NULL;
+ bluesky_cloudlog_stats_update(log, 1);
+ }
+ if (log->location_flags & CLOUDLOG_CLOUD) {
+ log->location_flags &= ~CLOUDLOG_JOURNAL;
+ }
+ g_mutex_unlock(log->lock);
+ }
}
-/* Drop clean data fromt the cache if needed due to memory pressure. */
+/* Drop clean data from the cache if needed. Clean data should generally be
+ * memory-mapped from log file or similar, so the kernel can drop this clean
+ * data from memory for us and hence memory management isn't too important.
+ * Mainly, we'll want to drop references to data that hasn't been accessed in a
+ * while so that it is possible to reclaim log segments on disk. */
static void flushd_clean(BlueSkyFS *fs)
{
g_mutex_lock(fs->lock);
inode_count = 1;
while (inode_count-- > 0) {
- if (g_atomic_int_get(&fs->cache_total) < bluesky_watermark_medium_total)
- break;
-
BlueSkyInode *inode;
if (fs->accessed_list.prev == NULL)
break;
inode = fs->accessed_list.prev->data;
+ uint64_t elapsed = bluesky_get_current_time() - inode->access_time;
+ if (elapsed < CACHE_DROP_DELAY)
+ break;
+
if (bluesky_verbose) {
g_log("bluesky/flushd", G_LOG_LEVEL_DEBUG,
"Considering dropping cached data for inode %"PRIu64,
if (!g_mutex_trylock(fs->flushd_lock))
return NULL;
flushd_dirty(fs);
- bluesky_cloudlog_write_log(fs);
+ flushd_cloud(fs);
flushd_clean(fs);
+ bluesky_cachefile_gc(fs);
g_mutex_unlock(fs->flushd_lock);
return NULL;
void bluesky_flushd_invoke_conditional(BlueSkyFS *fs)
{
- if (g_atomic_int_get(&fs->cache_dirty) < bluesky_watermark_high_dirty
- && g_atomic_int_get(&fs->cache_total) < bluesky_watermark_high_total)
+ if (g_atomic_int_get(&fs->cache_dirty) < bluesky_watermark_medium_dirty)
return;
if (bluesky_verbose) {
g_log("bluesky/flushd", G_LOG_LEVEL_DEBUG,
- "Too much data; invoking flushd: dirty=%d total=%d",
- g_atomic_int_get(&fs->cache_dirty),
- g_atomic_int_get(&fs->cache_total));
+ "Too much data; invoking flushd: dirty=%d",
+ g_atomic_int_get(&fs->cache_dirty));
}
bluesky_flushd_invoke(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) {
+ 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);
+ g_mutex_unlock(fs->lock);
+ }
}
/* Start a perpetually-running thread that flushes the cache occasionally. */