X-Git-Url: http://git.vrable.net/?a=blobdiff_plain;f=bluesky%2Fcache.c;h=2c1bc92c32a39f78ad639977c916923830caf613;hb=83fd6b61a6e092a22d4d5e59ed95f05f5e287f11;hp=72c181a9220552349b0263ffcfdbe082f3a7d335;hpb=966a43ffed492d387e0d75e56c3984d9001c15b1;p=bluesky.git diff --git a/bluesky/cache.c b/bluesky/cache.c index 72c181a..2c1bc92 100644 --- a/bluesky/cache.c +++ b/bluesky/cache.c @@ -14,161 +14,98 @@ #include "bluesky-private.h" #define WRITEBACK_DELAY (20 * 1000000) +#define CACHE_DROP_DELAY (20 * 1000000) -/* Filesystem caching and cache coherency. */ +/* Filesystem caching and cache coherency. There are actually a couple of + * different tasks that are performed here: + * - Forcing data to the log if needed to reclaim memory or simply if the + * data has been dirty in memory long enough. + * - Writing batches of data to the cloud. + */ -static void writeback_complete(gpointer a, gpointer i) +static void flushd_dirty_inode(BlueSkyInode *inode) { - BlueSkyInode *inode = (BlueSkyInode *)i; + BlueSkyFS *fs = inode->fs; - if (bluesky_verbose) { - g_log("bluesky/flushd", G_LOG_LEVEL_DEBUG, - "Writeback for inode %"PRIu64" complete", inode->inum); - } + g_mutex_lock(fs->lock); + bluesky_list_unlink(&fs->unlogged_list, inode->unlogged_list); + inode->unlogged_list = NULL; + g_mutex_unlock(fs->lock); - g_mutex_lock(inode->lock); + /* Inode is clean; nothing to do. */ + if (inode->change_count == inode->change_commit) + return; - 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); + if (bluesky_verbose) { + g_log("bluesky/flushd", G_LOG_LEVEL_DEBUG, + "Starting flush of inode %"PRIu64, inode->inum); } - g_mutex_unlock(inode->lock); + bluesky_inode_start_sync(inode); } -#if 0 -static void flushd_inode(gpointer value, gpointer user_data) +/* Check whether memory usage may have dropped below critical thresholds for + * waking up waiting threads. */ +void flushd_check_wakeup(BlueSkyFS *fs) { - BlueSkyFS *fs = (BlueSkyFS *)user_data; - - BlueSkyInode *inode = (BlueSkyInode *)value; - - g_mutex_lock(inode->lock); - - if (inode->change_count == inode->change_commit) { - uint64_t delay = bluesky_get_current_time() - inode->access_time; - if (delay >= CACHE_CLEAN_DELAY) { - drop_caches(inode); - - /* If the only references are the one we hold and the one in the - * filesystem inum->inode hash table... First check the refcount - * without the lock for speed, but if the check looks good verify - * it after taking the filesystem lock. */ - if (inode->refcount == 2) { - g_mutex_lock(fs->lock); - if (inode->refcount == 2) { - g_log("bluesky/flushd", G_LOG_LEVEL_DEBUG, - "Trying to drop inode %"PRIu64" from cache", - inode->inum); - if (g_hash_table_remove(fs->inodes, &inode->inum)) - bluesky_inode_unref(inode); - } - bluesky_list_unlink(&inode->fs->accessed_list, - inode->accessed_list); - inode->accessed_list = NULL; - bluesky_list_unlink(&inode->fs->dirty_list, - inode->dirty_list); - inode->dirty_list = NULL; - g_mutex_unlock(fs->lock); - } - } - - g_mutex_unlock(inode->lock); - bluesky_inode_unref(inode); - return; - } + int dirty = g_atomic_int_get(&fs->cache_dirty); + dirty += g_atomic_int_get(&fs->cache_log_dirty); - if (inode->change_pending) { - /* Waiting for an earlier writeback to finish, so don't start a new - * writeback yet. */ - g_mutex_unlock(inode->lock); - bluesky_inode_unref(inode); - return; - } - - uint64_t elapsed = bluesky_get_current_time() - inode->change_time; - if (elapsed < WRITEBACK_DELAY) { - /* Give a bit more time before starting writeback. */ - g_mutex_unlock(inode->lock); - bluesky_inode_unref(inode); - return; - } - - inode->change_pending = inode->change_count; - - g_log("bluesky/flushd", G_LOG_LEVEL_DEBUG, - "Starting flush of inode %"PRIu64, inode->inum); + if (dirty <= bluesky_watermark_high_dirty) + g_cond_broadcast(fs->flushd_cond); +} - /* Create a store barrier. All operations part of the writeback will be - * added to this barrier, so when the barrier completes we know that the - * writeback is finished. */ - BlueSkyStoreAsync *barrier = bluesky_store_async_new(fs->store); - barrier->op = STORE_OP_BARRIER; +/* 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); - bluesky_inode_start_sync(inode, barrier); + while (1) { + BlueSkyInode *inode; + if (fs->unlogged_list.prev == NULL) + break; + inode = fs->unlogged_list.prev->data; - bluesky_store_async_add_notifier(barrier, writeback_complete, inode); - bluesky_store_async_submit(barrier); - bluesky_store_async_unref(barrier); + if (bluesky_verbose) { + g_log("bluesky/flushd", G_LOG_LEVEL_DEBUG, + "Considering flushing inode %"PRIu64, inode->inum); + } - g_mutex_unlock(inode->lock); - bluesky_inode_unref(inode); -} -#endif + /* 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; -static void flushd_dirty_inode(BlueSkyInode *inode) -{ - BlueSkyFS *fs = inode->fs; + bluesky_inode_ref(inode); - g_mutex_lock(fs->lock); - bluesky_list_unlink(&fs->dirty_list, inode->dirty_list); - inode->dirty_list = NULL; - g_mutex_unlock(fs->lock); + g_mutex_unlock(fs->lock); - /* Inode is clean; nothing to do. */ - if (inode->change_count == inode->change_commit) - return; + g_mutex_lock(inode->lock); + flushd_dirty_inode(inode); + g_mutex_unlock(inode->lock); + bluesky_inode_unref(inode); - /* 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); + flushd_check_wakeup(fs); } - inode->change_pending = inode->change_count; - /* Create a store barrier. All operations part of the writeback will be - * added to this barrier, so when the barrier completes we know that the - * writeback is finished. */ - BlueSkyStoreAsync *barrier = bluesky_store_async_new(fs->store); - barrier->op = STORE_OP_BARRIER; + g_cond_broadcast(fs->flushd_cond); - bluesky_inode_start_sync(inode, barrier); - - bluesky_store_async_add_notifier(barrier, writeback_complete, inode); - bluesky_store_async_submit(barrier); - bluesky_store_async_unref(barrier); + g_mutex_unlock(fs->lock); } -/* Try to flush dirty data to disk, either due to memory pressure or due to - * timeouts. */ -static void flushd_dirty(BlueSkyFS *fs) +/* 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); @@ -181,7 +118,7 @@ static void flushd_dirty(BlueSkyFS *fs) 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 @@ -200,13 +137,25 @@ static void flushd_dirty(BlueSkyFS *fs) 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. */ @@ -216,7 +165,11 @@ static void drop_caches(BlueSkyInode *inode) bluesky_file_drop_cached(inode); } -/* 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); @@ -226,14 +179,15 @@ static void flushd_clean(BlueSkyFS *fs) 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, @@ -269,6 +223,7 @@ static gpointer flushd_task(BlueSkyFS *fs) if (!g_mutex_trylock(fs->flushd_lock)) return NULL; flushd_dirty(fs); + flushd_cloud(fs); flushd_clean(fs); g_mutex_unlock(fs->flushd_lock); @@ -282,16 +237,47 @@ void bluesky_flushd_invoke(BlueSkyFS *fs) 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. */ +static gpointer flushd_thread(BlueSkyFS *fs) +{ + while (TRUE) { + bluesky_flushd_invoke(fs); + struct timespec delay; + delay.tv_sec = 2; + delay.tv_nsec = 0; + nanosleep(&delay, NULL); + } + + return NULL; +} + +void bluesky_flushd_thread_launch(BlueSkyFS *fs) +{ + g_thread_create((GThreadFunc)flushd_thread, fs, FALSE, NULL); }