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-rw-r--r--fs/xfs/xfs_log_cil.c37
-rw-r--r--fs/xfs/xfs_log_priv.h24
-rw-r--r--fs/xfs/xfs_trace.h1
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),