X-Git-Url: http://git.vrable.net/?a=blobdiff_plain;f=bluesky%2Fcache.c;h=72c181a9220552349b0263ffcfdbe082f3a7d335;hb=966a43ffed492d387e0d75e56c3984d9001c15b1;hp=481390f74bf0e34ed47b81463572b871c16fadae;hpb=5b3aafc6c34c798f9ad74539f24c9b278e820163;p=bluesky.git diff --git a/bluesky/cache.c b/bluesky/cache.c index 481390f..72c181a 100644 --- a/bluesky/cache.c +++ b/bluesky/cache.c @@ -13,8 +13,7 @@ #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. */ @@ -22,28 +21,28 @@ 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); 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; - inode->change_pending = 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); } -/* 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); -} - +#if 0 static void flushd_inode(gpointer value, gpointer user_data) { BlueSkyFS *fs = (BlueSkyFS *)user_data; @@ -58,15 +57,24 @@ static void flushd_inode(gpointer value, gpointer user_data) drop_caches(inode); /* If the only references are the one we hold and the one in the - * filesystem inum->inode hash table... The check for a refcount - * of 2 shouldn't be necessary so it should be okay if there is a - * race on the check. */ + * 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_log("bluesky/flushd", G_LOG_LEVEL_DEBUG, - "Trying to drop inode %"PRIu64" from cache", inode->inum); g_mutex_lock(fs->lock); - if (g_hash_table_remove(fs->inodes, &inode->inum)) - bluesky_inode_unref(inode); + 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); } } @@ -112,33 +120,178 @@ static void flushd_inode(gpointer value, gpointer user_data) g_mutex_unlock(inode->lock); bluesky_inode_unref(inode); } +#endif -/* 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) +static void flushd_dirty_inode(BlueSkyInode *inode) { - GSList **list = (GSList **)user_data; - *list = g_slist_prepend(*list, value); - bluesky_inode_ref((BlueSkyInode *)value); + 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; + + /* 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; + + /* 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_start_sync(inode, barrier); + + bluesky_store_async_add_notifier(barrier, writeback_complete, inode); + bluesky_store_async_submit(barrier); + bluesky_store_async_unref(barrier); } -void bluesky_flushd_invoke(BlueSkyFS *fs) +/* Try to flush dirty data to disk, either due to memory pressure or due to + * timeouts. */ +static void flushd_dirty(BlueSkyFS *fs) { - GSList *list = NULL; + int64_t start_time = bluesky_get_current_time(); + g_mutex_lock(fs->lock); + + while (1) { + BlueSkyInode *inode; + if (fs->dirty_list.prev == NULL) + break; + inode = fs->dirty_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); + } + + 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 fromt the cache if needed due to memory pressure. */ +static void flushd_clean(BlueSkyFS *fs) +{ g_mutex_lock(fs->lock); - g_hash_table_foreach(fs->inodes, gather_inodes, &list); + + size_t inode_count = g_hash_table_size(fs->inodes); + if (!inode_count) + 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; + + if (bluesky_verbose) { + g_log("bluesky/flushd", G_LOG_LEVEL_DEBUG, + "Considering dropping cached data for inode %"PRIu64, + inode->inum); + } + + bluesky_inode_ref(inode); + + g_mutex_unlock(fs->lock); + + g_mutex_lock(inode->lock); + + 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); +} + +/* Run the flush daemon for a single iteration, though if it is already + * executing returns immediately. */ +static gpointer flushd_task(BlueSkyFS *fs) +{ + if (!g_mutex_trylock(fs->flushd_lock)) + return NULL; + flushd_dirty(fs); + flushd_clean(fs); + g_mutex_unlock(fs->flushd_lock); + + return NULL; +} - list = g_slist_reverse(list); - g_slist_foreach(list, flushd_inode, fs); +void bluesky_flushd_invoke(BlueSkyFS *fs) +{ + g_thread_create((GThreadFunc)flushd_task, fs, FALSE, 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) + 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)); + } - g_slist_free(list); + bluesky_flushd_invoke(fs); }