After removing a monitor group, its RMID may not be freed immediately
unless its llc_occupancy is less than the re-allocation threshold. If
turning up the threshold, the RMID can be reused. In order to know how
much the threshold should be, it's necessary to acquire the llc_occupancy.
The patch series provides a new tracepoint to track the llc_occupancy.
Changes since v1:
- Rename pseudo_lock_event.h instead of creating a new header file.
- Modify names used in the tracepoint.
- Update changelog.
Changes since v2:
- Fix typo and use the x86/resctrl subject prefix in the cover letter.
- Track both CLOSID and RMID in the tracepoint.
- Remove the details on how perf can be used in patch2's changelog.
Changes since v3:
- Put the tracepoint in the 'else' section of the if/else after
resctrl_arch_rmid_read().
- Modify names used in the tracepoint.
- Document the properties of the tracepoint.
Haifeng Xu (2):
x86/resctrl: Rename pseudo_lock_event.h to trace.h
x86/resctrl: Add tracepoint for llc_occupancy tracking
Documentation/arch/x86/resctrl.rst | 8 +++++++
arch/x86/kernel/cpu/resctrl/monitor.c | 9 ++++++++
arch/x86/kernel/cpu/resctrl/pseudo_lock.c | 2 +-
.../resctrl/{pseudo_lock_event.h => trace.h} | 22 ++++++++++++++++---
4 files changed, 37 insertions(+), 4 deletions(-)
rename arch/x86/kernel/cpu/resctrl/{pseudo_lock_event.h => trace.h} (57%)
--
2.25.1
Now only pseudo-locking part uses tracepoints to do event tracking, but
other parts of resctrl may need new tracepoints. It is unnecessary to
create separate header files and define CREATE_TRACE_POINTS in different
c files which fragments the resctrl tracing.
Therefore, give the resctrl tracepoint header file a generic name to
support its use for tracepoints that are not specific to pseudo-locking.
No functional change.
Signed-off-by: Haifeng Xu <[email protected]>
Suggested-by: Reinette Chatre <[email protected]>
---
arch/x86/kernel/cpu/resctrl/pseudo_lock.c | 2 +-
.../x86/kernel/cpu/resctrl/{pseudo_lock_event.h => trace.h} | 6 +++---
2 files changed, 4 insertions(+), 4 deletions(-)
rename arch/x86/kernel/cpu/resctrl/{pseudo_lock_event.h => trace.h} (88%)
diff --git a/arch/x86/kernel/cpu/resctrl/pseudo_lock.c b/arch/x86/kernel/cpu/resctrl/pseudo_lock.c
index 884b88e25141..492c8e28c4ce 100644
--- a/arch/x86/kernel/cpu/resctrl/pseudo_lock.c
+++ b/arch/x86/kernel/cpu/resctrl/pseudo_lock.c
@@ -31,7 +31,7 @@
#include "internal.h"
#define CREATE_TRACE_POINTS
-#include "pseudo_lock_event.h"
+#include "trace.h"
/*
* The bits needed to disable hardware prefetching varies based on the
diff --git a/arch/x86/kernel/cpu/resctrl/pseudo_lock_event.h b/arch/x86/kernel/cpu/resctrl/trace.h
similarity index 88%
rename from arch/x86/kernel/cpu/resctrl/pseudo_lock_event.h
rename to arch/x86/kernel/cpu/resctrl/trace.h
index 428ebbd4270b..ed5c66b8ab0b 100644
--- a/arch/x86/kernel/cpu/resctrl/pseudo_lock_event.h
+++ b/arch/x86/kernel/cpu/resctrl/trace.h
@@ -2,7 +2,7 @@
#undef TRACE_SYSTEM
#define TRACE_SYSTEM resctrl
-#if !defined(_TRACE_PSEUDO_LOCK_H) || defined(TRACE_HEADER_MULTI_READ)
+#if !defined(_TRACE_RESCTRL_H) || defined(TRACE_HEADER_MULTI_READ)
#define _TRACE_PSEUDO_LOCK_H
#include <linux/tracepoint.h>
@@ -35,9 +35,9 @@ TRACE_EVENT(pseudo_lock_l3,
TP_printk("hits=%llu miss=%llu",
__entry->l3_hits, __entry->l3_miss));
-#endif /* _TRACE_PSEUDO_LOCK_H */
+#endif /* _TRACE_RESCTRL_H */
#undef TRACE_INCLUDE_PATH
#define TRACE_INCLUDE_PATH .
-#define TRACE_INCLUDE_FILE pseudo_lock_event
+#define TRACE_INCLUDE_FILE trace
#include <trace/define_trace.h>
--
2.25.1
In our production environment, after removing monitor groups, those unused
RMIDs get stuck in the limbo list forever because their llc_occupancy are
always larger than the threshold. But the unused RMIDs can be successfully
freed by turning up the threshold.
In order to know how much the threshold should be, perf can be used to
acquire the llc_occupancy of RMIDs in each rdt domain.
Instead of using perf tool to track llc_occupancy and filter the log
manually, it is more convenient for users to use tracepoint to do this
work. So add a new tracepoint that shows the llc_occupancy of busy RMIDs
when scanning the limbo list.
Signed-off-by: Haifeng Xu <[email protected]>
Suggested-by: Reinette Chatre <[email protected]>
Suggested-by: James Morse <[email protected]>
---
Documentation/arch/x86/resctrl.rst | 8 ++++++++
arch/x86/kernel/cpu/resctrl/monitor.c | 9 +++++++++
arch/x86/kernel/cpu/resctrl/trace.h | 16 ++++++++++++++++
3 files changed, 33 insertions(+)
diff --git a/Documentation/arch/x86/resctrl.rst b/Documentation/arch/x86/resctrl.rst
index a6279df64a9d..dd3507dc765c 100644
--- a/Documentation/arch/x86/resctrl.rst
+++ b/Documentation/arch/x86/resctrl.rst
@@ -478,6 +478,14 @@ if non-contiguous 1s value is supported. On a system with a 20-bit mask
each bit represents 5% of the capacity of the cache. You could partition
the cache into four equal parts with masks: 0x1f, 0x3e0, 0x7c00, 0xf8000.
+Tracepoint - mon_llc_occupancy_limbo
+------------------------------------
+This tracepoint gives you the precise occupancy values for a subset of RMID
+that are not immediately available for allocation. This can't be relied on
+to produce output every second, it may be necessary to attempt to create an
+empty monitor group to force an update. Output may only be produced if creation
+of a control or monitor group fails.
+
Memory bandwidth Allocation and monitoring
==========================================
diff --git a/arch/x86/kernel/cpu/resctrl/monitor.c b/arch/x86/kernel/cpu/resctrl/monitor.c
index c34a35ec0f03..60b6a29a9e29 100644
--- a/arch/x86/kernel/cpu/resctrl/monitor.c
+++ b/arch/x86/kernel/cpu/resctrl/monitor.c
@@ -24,6 +24,7 @@
#include <asm/resctrl.h>
#include "internal.h"
+#include "trace.h"
/**
* struct rmid_entry - dirty tracking for all RMID.
@@ -354,6 +355,14 @@ void __check_limbo(struct rdt_domain *d, bool force_free)
rmid_dirty = true;
} else {
rmid_dirty = (val >= resctrl_rmid_realloc_threshold);
+
+ /* x86's CLOSID and RMID are independent numbers, so the entry's
+ * closid is a invalid CLOSID. But on arm64, the RMID value isn't
+ * a unique number for each CLOSID. It's necessary to track both
+ * CLOSID and RMID because there may be dependencies between each
+ * other on some architectures.
+ */
+ trace_mon_llc_occupancy_limbo(entry->closid, entry->rmid, d->id, val);
}
if (force_free || !rmid_dirty) {
diff --git a/arch/x86/kernel/cpu/resctrl/trace.h b/arch/x86/kernel/cpu/resctrl/trace.h
index ed5c66b8ab0b..b310b4985b94 100644
--- a/arch/x86/kernel/cpu/resctrl/trace.h
+++ b/arch/x86/kernel/cpu/resctrl/trace.h
@@ -35,6 +35,22 @@ TRACE_EVENT(pseudo_lock_l3,
TP_printk("hits=%llu miss=%llu",
__entry->l3_hits, __entry->l3_miss));
+TRACE_EVENT(mon_llc_occupancy_limbo,
+ TP_PROTO(u32 ctrl_hw_id, u32 mon_hw_id, int domain_id, u64 llc_occupancy_bytes),
+ TP_ARGS(ctrl_hw_id, mon_hw_id, domain_id, llc_occupancy_bytes),
+ TP_STRUCT__entry(__field(u32, ctrl_hw_id)
+ __field(u32, mon_hw_id)
+ __field(int, domain_id)
+ __field(u64, llc_occupancy_bytes)),
+ TP_fast_assign(__entry->ctrl_hw_id = ctrl_hw_id;
+ __entry->mon_hw_id = mon_hw_id;
+ __entry->domain_id = domain_id;
+ __entry->llc_occupancy_bytes = llc_occupancy_bytes;),
+ TP_printk("ctrl_hw_id=%u mon_hw_id=%u domain_d=%d llc_occupancy_bytes=%llu",
+ __entry->ctrl_hw_id, __entry->mon_hw_id, __entry->domain_id,
+ __entry->llc_occupancy_bytes)
+ );
+
#endif /* _TRACE_RESCTRL_H */
#undef TRACE_INCLUDE_PATH
--
2.25.1