X-Git-Url: http://git.vrable.net/?a=blobdiff_plain;f=bluesky%2Fcache.c;h=58b7cd6f1ac79c6b67af07fc4ece5979f872312d;hb=e49fed25d000a51b316b480c1bfb1b00c1f5d345;hp=211c2b9e5b2ecbad22e77390a468f4408cba632e;hpb=de946bbcea4c0bc0c92a858eae4d5c668e923c83;p=bluesky.git diff --git a/bluesky/cache.c b/bluesky/cache.c index 211c2b9..58b7cd6 100644 --- a/bluesky/cache.c +++ b/bluesky/cache.c @@ -13,17 +13,24 @@ #include "bluesky-private.h" -#define WRITEBACK_DELAY (5 * 1000000) -#define CACHE_CLEAN_DELAY (30 * 1000000) +#define WRITEBACK_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. + */ +#if 0 static void writeback_complete(gpointer a, gpointer i) { BlueSkyInode *inode = (BlueSkyInode *)i; - g_log("bluesky/flushd", G_LOG_LEVEL_DEBUG, - "Writeback for inode %"PRIu64" complete", inode->inum); + if (bluesky_verbose) { + g_log("bluesky/flushd", G_LOG_LEVEL_DEBUG, + "Writeback for inode %"PRIu64" complete", inode->inum); + } g_mutex_lock(inode->lock); @@ -40,118 +47,177 @@ static void writeback_complete(gpointer a, gpointer i) g_mutex_unlock(inode->lock); } +#endif -/* Drop cached data for a given inode, if it is clean. inode must be locked. */ -static void drop_caches(BlueSkyInode *inode) +static void flushd_dirty_inode(BlueSkyInode *inode) { - if (inode->type == BLUESKY_REGULAR) - bluesky_file_drop_cached(inode); + BlueSkyFS *fs = inode->fs; + + g_mutex_lock(fs->lock); + bluesky_list_unlink(&fs->dirty_list, inode->dirty_list); + inode->dirty_list = NULL; + g_mutex_unlock(fs->lock); + + /* Inode is clean; nothing to do. */ + if (inode->change_count == inode->change_commit) + return; + + if (bluesky_verbose) { + g_log("bluesky/flushd", G_LOG_LEVEL_DEBUG, + "Starting flush of inode %"PRIu64, inode->inum); + } + + bluesky_inode_start_sync(inode); } -static void flushd_inode(gpointer value, gpointer user_data) +/* Try to flush dirty data to disk, either due to memory pressure or due to + * timeouts. */ +static void flushd_dirty(BlueSkyFS *fs) { - BlueSkyFS *fs = (BlueSkyFS *)user_data; - - BlueSkyInode *inode = (BlueSkyInode *)value; + int64_t start_time = bluesky_get_current_time(); + g_mutex_lock(fs->lock); - g_mutex_lock(inode->lock); + while (1) { + BlueSkyInode *inode; + if (fs->dirty_list.prev == NULL) + break; + inode = fs->dirty_list.prev->data; - 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); - } + 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); - return; - } + /* 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; - 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; - } + bluesky_inode_ref(inode); + + g_mutex_unlock(fs->lock); - uint64_t elapsed = bluesky_get_current_time() - inode->change_time; - if (elapsed < WRITEBACK_DELAY) { - /* Give a bit more time before starting writeback. */ + g_mutex_lock(inode->lock); + flushd_dirty_inode(inode); g_mutex_unlock(inode->lock); bluesky_inode_unref(inode); - return; + + g_mutex_lock(fs->lock); } - inode->change_pending = inode->change_count; + g_mutex_unlock(fs->lock); +} + +/* Drop cached data for a given inode, if it is clean. inode must be locked. */ +static void drop_caches(BlueSkyInode *inode) +{ + if (inode->type == BLUESKY_REGULAR) + bluesky_file_drop_cached(inode); +} + +/* Drop clean data from the cache if needed due to memory pressure. */ +static void flushd_clean(BlueSkyFS *fs) +{ + g_mutex_lock(fs->lock); - g_log("bluesky/flushd", G_LOG_LEVEL_DEBUG, - "Starting flush of inode %"PRIu64, inode->inum); + size_t inode_count = g_hash_table_size(fs->inodes); + if (!inode_count) + inode_count = 1; + + while (inode_count-- > 0) { +#if 0 + if (g_atomic_int_get(&fs->cache_total) < bluesky_watermark_medium_total) + break; +#endif + + BlueSkyInode *inode; + if (fs->accessed_list.prev == NULL) + break; + inode = fs->accessed_list.prev->data; + + if (bluesky_verbose) { + g_log("bluesky/flushd", G_LOG_LEVEL_DEBUG, + "Considering dropping cached data for inode %"PRIu64, + inode->inum); + } - /* 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; + bluesky_inode_ref(inode); - bluesky_inode_start_sync(inode, barrier); + g_mutex_unlock(fs->lock); - bluesky_store_async_add_notifier(barrier, writeback_complete, inode); - bluesky_store_async_submit(barrier); - bluesky_store_async_unref(barrier); + g_mutex_lock(inode->lock); - g_mutex_unlock(inode->lock); - bluesky_inode_unref(inode); + g_mutex_lock(fs->lock); + bluesky_list_unlink(&fs->accessed_list, inode->accessed_list); + inode->accessed_list = bluesky_list_prepend(&fs->accessed_list, inode); + g_mutex_unlock(fs->lock); + + drop_caches(inode); + + g_mutex_unlock(inode->lock); + bluesky_inode_unref(inode); + + g_mutex_lock(fs->lock); + } + + g_mutex_unlock(fs->lock); } -/* Scan through the cache for dirty data and start flushing it to stable - * storage. This does not guarantee that data is committed when it returns. - * Instead, this can be called occasionally to ensure that dirty data is - * gradually flushed. - * - * We do not want to hold the filesystem lock while flushing individual inodes, - * a that could lead to deadlock. So first scan through the inode table to get - * a reference to all inodes, then process that queue of inodes after dropping - * the filesystem lock. */ -static void gather_inodes(gpointer key, gpointer value, gpointer user_data) +/* Run the flush daemon for a single iteration, though if it is already + * executing returns immediately. */ +static gpointer flushd_task(BlueSkyFS *fs) { - GSList **list = (GSList **)user_data; - *list = g_slist_prepend(*list, value); - bluesky_inode_ref((BlueSkyInode *)value); + if (!g_mutex_trylock(fs->flushd_lock)) + return NULL; + flushd_dirty(fs); + bluesky_cloudlog_write_log(fs); + flushd_clean(fs); + g_mutex_unlock(fs->flushd_lock); + + return NULL; } void bluesky_flushd_invoke(BlueSkyFS *fs) { - GSList *list = NULL; + g_thread_create((GThreadFunc)flushd_task, fs, FALSE, NULL); +} - g_mutex_lock(fs->lock); - g_hash_table_foreach(fs->inodes, gather_inodes, &list); - g_mutex_unlock(fs->lock); +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) + 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)); + } + + bluesky_flushd_invoke(fs); +} + +/* 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); + } - list = g_slist_reverse(list); - g_slist_foreach(list, flushd_inode, fs); + return NULL; +} - g_slist_free(list); +void bluesky_flushd_thread_launch(BlueSkyFS *fs) +{ + g_thread_create((GThreadFunc)flushd_thread, fs, FALSE, NULL); }