[PATCH 35/45] xfs: introduce per-cpu CIL tracking sructure

Dave Chinner
2021-03-05T05:12:27Z

From: Dave Chinner <dchinner@redhat.com>

The CIL push lock is highly contended on larger machines, becoming a
hard bottleneck that about 700,000 transaction commits/s on >16p
machines. To address this, start moving the CIL tracking
infrastructure to utilise per-CPU structures.

We need to track the space used, the amount of log reservation space
reserved to write the CIL, the log items in the CIL and the busy
extents that need to be completed by the CIL commit. This requires
a couple of per-cpu counters, an unordered per-cpu list and a
globally ordered per-cpu list.

Create a per-cpu structure to hold these and all the management
interfaces needed, as well as the hooks to handle hotplug CPUs.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
---
fs/xfs/xfs_log_cil.c | 94 ++++++++++++++++++++++++++++++++++++++
fs/xfs/xfs_log_priv.h | 15 ++++++
include/linux/cpuhotplug.h | 1 +
3 files changed, 110 insertions(+)

diff --git a/fs/xfs/xfs_log_cil.c b/fs/xfs/xfs_log_cil.c
index f8fb2f59e24c..1bcf0d423d30 100644
--- a/fs/xfs/xfs_log_cil.c
+++ b/fs/xfs/xfs_log_cil.c
@@ -1365,6 +1365,93 @@ xfs_log_item_in_current_chkpt(
return true;
}

+#ifdef CONFIG_HOTPLUG_CPU
+static LIST_HEAD(xlog_cil_pcp_list);
+static DEFINE_SPINLOCK(xlog_cil_pcp_lock);
+static bool xlog_cil_pcp_init;
+
+static int
+xlog_cil_pcp_dead(
+ unsigned int cpu)
+{
+ struct xfs_cil *cil;
+
+ spin_lock(&xlog_cil_pcp_lock);
+ list_for_each_entry(cil, &xlog_cil_pcp_list, xc_pcp_list) {
+ /* move stuff on dead CPU to context */
+ }
+ spin_unlock(&xlog_cil_pcp_lock);
+ return 0;
+}
+
+static int
+xlog_cil_pcp_hpadd(
+ struct xfs_cil *cil)
+{
+ if (!xlog_cil_pcp_init) {
+ int ret;
+ ret = cpuhp_setup_state_nocalls(CPUHP_XFS_CIL_DEAD,
+ "xfs/cil_pcp:dead", NULL,
+ xlog_cil_pcp_dead);
+ if (ret < 0) {
+ xfs_warn(cil->xc_log->l_mp,
+ "Failed to initialise CIL hotplug, error %d. XFS is non-functional.",
+ ret);
+ ASSERT(0);
+ return -ENOMEM;
+ }
+ xlog_cil_pcp_init = true;
+ }
+
+ INIT_LIST_HEAD(&cil->xc_pcp_list);
+ spin_lock(&xlog_cil_pcp_lock);
+ list_add(&cil->xc_pcp_list, &xlog_cil_pcp_list);
+ spin_unlock(&xlog_cil_pcp_lock);
+ return 0;
+}
+
+static void
+xlog_cil_pcp_hpremove(
+ struct xfs_cil *cil)
+{
+ spin_lock(&xlog_cil_pcp_lock);
+ list_del(&cil->xc_pcp_list);
+ spin_unlock(&xlog_cil_pcp_lock);
+}
+
+#else /* !CONFIG_HOTPLUG_CPU */
+static inline void xlog_cil_pcp_hpadd(struct xfs_cil *cil) {}
+static inline void xlog_cil_pcp_hpremove(struct xfs_cil *cil) {}
+#endif
+
+static void __percpu *
+xlog_cil_pcp_alloc(
+ struct xfs_cil *cil)
+{
+ struct xlog_cil_pcp *cilpcp;
+
+ cilpcp = alloc_percpu(struct xlog_cil_pcp);
+ if (!cilpcp)
+ return NULL;
+
+ if (xlog_cil_pcp_hpadd(cil) < 0) {
+ free_percpu(cilpcp);
+ return NULL;
+ }
+ return cilpcp;
+}
+
+static void
+xlog_cil_pcp_free(
+ struct xfs_cil *cil,
+ struct xlog_cil_pcp *cilpcp)
+{
+ if (!cilpcp)
+ return;
+ xlog_cil_pcp_hpremove(cil);
+ free_percpu(cilpcp);
+}
+
/*
* Perform initial CIL structure initialisation.
*/
@@ -1379,6 +1466,12 @@ xlog_cil_init(
if (!cil)
return -ENOMEM;

+ cil->xc_pcp = xlog_cil_pcp_alloc(cil);
+ if (!cil->xc_pcp) {
+ kmem_free(cil);
+ return -ENOMEM;
+ }
+
INIT_LIST_HEAD(&cil->xc_cil);
INIT_LIST_HEAD(&cil->xc_committing);
spin_lock_init(&cil->xc_cil_lock);
@@ -1409,6 +1502,7 @@ xlog_cil_destroy(

ASSERT(list_empty(&cil->xc_cil));
ASSERT(test_bit(XLOG_CIL_EMPTY, &cil->xc_flags));
+ xlog_cil_pcp_free(cil, cil->xc_pcp);
kmem_free(cil);
}

diff --git a/fs/xfs/xfs_log_priv.h b/fs/xfs/xfs_log_priv.h
index e72d14c76e03..2562f29c8986 100644
--- a/fs/xfs/xfs_log_priv.h
+++ b/fs/xfs/xfs_log_priv.h
@@ -231,6 +231,16 @@ struct xfs_cil_ctx {
struct work_struct push_work;
};

+/*
+ * Per-cpu CIL tracking items
+ */
+struct xlog_cil_pcp {
+ uint32_t space_used;
+ uint32_t curr_res;
+ struct list_head busy_extents;
+ struct list_head log_items;
+};
+
/*
* Committed Item List structure
*
@@ -264,6 +274,11 @@ struct xfs_cil {
wait_queue_head_t xc_commit_wait;
xfs_csn_t xc_current_sequence;
wait_queue_head_t xc_push_wait; /* background push throttle */
+
+ struct xlog_cil_pcp __percpu *xc_pcp;
+#ifdef CONFIG_HOTPLUG_CPU
+ struct list_head xc_pcp_list;
+#endif
} ____cacheline_aligned_in_smp;

/* xc_flags bit values */
diff --git a/include/linux/cpuhotplug.h b/include/linux/cpuhotplug.h
index f14adb882338..b13b21d825b3 100644
--- a/include/linux/cpuhotplug.h
+++ b/include/linux/cpuhotplug.h
@@ -52,6 +52,7 @@ enum cpuhp_state {
CPUHP_FS_BUFF_DEAD,
CPUHP_PRINTK_DEAD,
CPUHP_MM_MEMCQ_DEAD,
+ CPUHP_XFS_CIL_DEAD,
CPUHP_PERCPU_CNT_DEAD,
CPUHP_RADIX_DEAD,
CPUHP_PAGE_ALLOC_DEAD,
--
2.28.0