KVM: Don't pre-reserve xarray entries when storing empty/NULL attributesgrafted

Skip the xarray reservation loop when clearing all memory attributes, as
storing NULL only erases the entry and never needs to allocate, so no
reservation (and no cleanup of a failed one) is required in that case.

Suggested-by: Sean Christopherson <seanjc@google.com>
Cc: David Ballesteros <davimaba.v@proton.me>
Signed-off-by: Zeng Chi <zengchi@kylinos.cn>
Link: https://patch.msgid.link/20260921102442.1232375-1-zeng_chi911@163.com
[sean: split to separate patch]
Signed-off-by: Sean Christopherson <seanjc@google.com>

1 files changed, 106 insertions, 0 deletions

diff --git a/include/trace/events/memcg.h b/include/trace/events/memcg.h
new file mode 100644
index 000000000..51b62c593
--- /dev/null
+++ b/include/trace/events/memcg.h
@@ -0,0 +1,106 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#undef TRACE_SYSTEM
+#define TRACE_SYSTEM memcg
+
+#if !defined(_TRACE_MEMCG_H) || defined(TRACE_HEADER_MULTI_READ)
+#define _TRACE_MEMCG_H
+
+#include <linux/memcontrol.h>
+#include <linux/tracepoint.h>
+
+
+DECLARE_EVENT_CLASS(memcg_rstat_stats,
+
+	TP_PROTO(struct mem_cgroup *memcg, int item, long val),
+
+	TP_ARGS(memcg, item, val),
+
+	TP_STRUCT__entry(
+		__field(u64, id)
+		__field(int, item)
+		__field(long, val)
+	),
+
+	TP_fast_assign(
+		__entry->id = cgroup_id(memcg->css.cgroup);
+		__entry->item = item;
+		__entry->val = val;
+	),
+
+	TP_printk("memcg_id=%llu item=%d val=%ld",
+		  __entry->id, __entry->item, __entry->val)
+);
+
+DEFINE_EVENT(memcg_rstat_stats, mod_memcg_state,
+
+	TP_PROTO(struct mem_cgroup *memcg, int item, long val),
+
+	TP_ARGS(memcg, item, val)
+);
+
+DEFINE_EVENT(memcg_rstat_stats, mod_memcg_lruvec_state,
+
+	TP_PROTO(struct mem_cgroup *memcg, int item, long val),
+
+	TP_ARGS(memcg, item, val)
+);
+
+DECLARE_EVENT_CLASS(memcg_rstat_events,
+
+	TP_PROTO(struct mem_cgroup *memcg, int item, unsigned long val),
+
+	TP_ARGS(memcg, item, val),
+
+	TP_STRUCT__entry(
+		__field(u64, id)
+		__field(int, item)
+		__field(unsigned long, val)
+	),
+
+	TP_fast_assign(
+		__entry->id = cgroup_id(memcg->css.cgroup);
+		__entry->item = item;
+		__entry->val = val;
+	),
+
+	TP_printk("memcg_id=%llu item=%d val=%lu",
+		  __entry->id, __entry->item, __entry->val)
+);
+
+DEFINE_EVENT(memcg_rstat_events, count_memcg_events,
+
+	TP_PROTO(struct mem_cgroup *memcg, int item, unsigned long val),
+
+	TP_ARGS(memcg, item, val)
+);
+
+TRACE_EVENT(memcg_flush_stats,
+
+	TP_PROTO(struct mem_cgroup *memcg, s64 stats_updates,
+		bool force, bool needs_flush),
+
+	TP_ARGS(memcg, stats_updates, force, needs_flush),
+
+	TP_STRUCT__entry(
+		__field(u64, id)
+		__field(s64, stats_updates)
+		__field(bool, force)
+		__field(bool, needs_flush)
+	),
+
+	TP_fast_assign(
+		__entry->id = cgroup_id(memcg->css.cgroup);
+		__entry->stats_updates = stats_updates;
+		__entry->force = force;
+		__entry->needs_flush = needs_flush;
+	),
+
+	TP_printk("memcg_id=%llu stats_updates=%lld force=%d needs_flush=%d",
+		__entry->id, __entry->stats_updates,
+		__entry->force, __entry->needs_flush)
+);
+
+#endif /* _TRACE_MEMCG_H */
+
+/* This part must be outside protection */
+#include <trace/define_trace.h>