diff options
| -rw-r--r-- | fs/xfs/xfs_log_cil.c | 37 | ||||
| -rw-r--r-- | fs/xfs/xfs_log_priv.h | 24 | ||||
| -rw-r--r-- | fs/xfs/xfs_trace.h | 1 |
3 files changed, 58 insertions, 4 deletions
diff --git a/fs/xfs/xfs_log_cil.c b/fs/xfs/xfs_log_cil.c index e3dd405ea767..b43f0e8f43f2 100644 --- a/fs/xfs/xfs_log_cil.c +++ b/fs/xfs/xfs_log_cil.c @@ -669,6 +669,11 @@ xlog_cil_push_work( ASSERT(push_seq <= ctx->sequence); /* + * Wake up any background push waiters now this context is being pushed. + */ + wake_up_all(&ctx->push_wait); + + /* * Check if we've anything to push. If there is nothing, then we don't * move on to a new sequence number and so we have to be able to push * this sequence again later. @@ -744,6 +749,7 @@ xlog_cil_push_work( */ INIT_LIST_HEAD(&new_ctx->committing); INIT_LIST_HEAD(&new_ctx->busy_extents); + init_waitqueue_head(&new_ctx->push_wait); new_ctx->sequence = ctx->sequence + 1; new_ctx->cil = cil; cil->xc_ctx = new_ctx; @@ -891,7 +897,7 @@ out_abort: */ static void xlog_cil_push_background( - struct xlog *log) + struct xlog *log) __releases(cil->xc_ctx_lock) { struct xfs_cil *cil = log->l_cilp; @@ -905,14 +911,36 @@ xlog_cil_push_background( * don't do a background push if we haven't used up all the * space available yet. */ - if (cil->xc_ctx->space_used < XLOG_CIL_SPACE_LIMIT(log)) + if (cil->xc_ctx->space_used < XLOG_CIL_SPACE_LIMIT(log)) { + up_read(&cil->xc_ctx_lock); return; + } spin_lock(&cil->xc_push_lock); if (cil->xc_push_seq < cil->xc_current_sequence) { cil->xc_push_seq = cil->xc_current_sequence; queue_work(log->l_mp->m_cil_workqueue, &cil->xc_push_work); } + + /* + * Drop the context lock now, we can't hold that if we need to sleep + * because we are over the blocking threshold. The push_lock is still + * held, so blocking threshold sleep/wakeup is still correctly + * serialised here. + */ + up_read(&cil->xc_ctx_lock); + + /* + * If we are well over the space limit, throttle the work that is being + * done until the push work on this context has begun. + */ + if (cil->xc_ctx->space_used >= XLOG_CIL_BLOCKING_SPACE_LIMIT(log)) { + trace_xfs_log_cil_wait(log, cil->xc_ctx->ticket); + ASSERT(cil->xc_ctx->space_used < log->l_logsize); + xlog_wait(&cil->xc_ctx->push_wait, &cil->xc_push_lock); + return; + } + spin_unlock(&cil->xc_push_lock); } @@ -1032,9 +1060,9 @@ xfs_log_commit_cil( if (lip->li_ops->iop_committing) lip->li_ops->iop_committing(lip, xc_commit_lsn); } - xlog_cil_push_background(log); - up_read(&cil->xc_ctx_lock); + /* xlog_cil_push_background() releases cil->xc_ctx_lock */ + xlog_cil_push_background(log); } /* @@ -1193,6 +1221,7 @@ xlog_cil_init( INIT_LIST_HEAD(&ctx->committing); INIT_LIST_HEAD(&ctx->busy_extents); + init_waitqueue_head(&ctx->push_wait); ctx->sequence = 1; ctx->cil = cil; cil->xc_ctx = ctx; diff --git a/fs/xfs/xfs_log_priv.h b/fs/xfs/xfs_log_priv.h index 938edd19a8a6..ec22c7a3867f 100644 --- a/fs/xfs/xfs_log_priv.h +++ b/fs/xfs/xfs_log_priv.h @@ -240,6 +240,7 @@ struct xfs_cil_ctx { struct xfs_log_vec *lv_chain; /* logvecs being pushed */ struct list_head iclog_entry; struct list_head committing; /* ctx committing list */ + wait_queue_head_t push_wait; /* background push throttle */ struct work_struct discard_endio_work; }; @@ -337,10 +338,33 @@ struct xfs_cil { * buffer window (32MB) as measurements have shown this to be roughly the * point of diminishing performance increases under highly concurrent * modification workloads. + * + * To prevent the CIL from overflowing upper commit size bounds, we introduce a + * new threshold at which we block committing transactions until the background + * CIL commit commences and switches to a new context. While this is not a hard + * limit, it forces the process committing a transaction to the CIL to block and + * yeild the CPU, giving the CIL push work a chance to be scheduled and start + * work. This prevents a process running lots of transactions from overfilling + * the CIL because it is not yielding the CPU. We set the blocking limit at + * twice the background push space threshold so we keep in line with the AIL + * push thresholds. + * + * Note: this is not a -hard- limit as blocking is applied after the transaction + * is inserted into the CIL and the push has been triggered. It is largely a + * throttling mechanism that allows the CIL push to be scheduled and run. A hard + * limit will be difficult to implement without introducing global serialisation + * in the CIL commit fast path, and it's not at all clear that we actually need + * such hard limits given the ~7 years we've run without a hard limit before + * finding the first situation where a checkpoint size overflow actually + * occurred. Hence the simple throttle, and an ASSERT check to tell us that + * we've overrun the max size. */ #define XLOG_CIL_SPACE_LIMIT(log) \ min_t(int, (log)->l_logsize >> 3, BBTOB(XLOG_TOTAL_REC_SHIFT(log)) << 4) +#define XLOG_CIL_BLOCKING_SPACE_LIMIT(log) \ + (XLOG_CIL_SPACE_LIMIT(log) * 2) + /* * ticket grant locks, queues and accounting have their own cachlines * as these are quite hot and can be operated on concurrently. diff --git a/fs/xfs/xfs_trace.h b/fs/xfs/xfs_trace.h index f7f12d312fd3..a4323a63438d 100644 --- a/fs/xfs/xfs_trace.h +++ b/fs/xfs/xfs_trace.h @@ -1015,6 +1015,7 @@ DEFINE_LOGGRANT_EVENT(xfs_log_ticket_regrant_sub); DEFINE_LOGGRANT_EVENT(xfs_log_ticket_ungrant); DEFINE_LOGGRANT_EVENT(xfs_log_ticket_ungrant_sub); DEFINE_LOGGRANT_EVENT(xfs_log_ticket_ungrant_exit); +DEFINE_LOGGRANT_EVENT(xfs_log_cil_wait); DECLARE_EVENT_CLASS(xfs_log_item_class, TP_PROTO(struct xfs_log_item *lip), |