x86/mm: Add tracepoints for TLB flushes
We don't have any good way to figure out what kinds of flushes
are being attempted. Right now, we can try to use the vm
counters, but those only tell us what we actually did with the
hardware (one-by-one vs full) and don't tell us what was actually
_requested_.
This allows us to select out "interesting" TLB flushes that we
might want to optimize (like the ranged ones) and ignore the ones
that we have very little control over (the ones at context
switch).
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Link: http://lkml.kernel.org/r/20140731154059.4C96CBA5@viggo.jf.intel.com
Acked-by: Rik van Riel <riel@redhat.com>
Cc: Mel Gorman <mgorman@suse.de>
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
diff --git a/arch/x86/include/asm/mmu_context.h b/arch/x86/include/asm/mmu_context.h
index be12c53..166af2a 100644
--- a/arch/x86/include/asm/mmu_context.h
+++ b/arch/x86/include/asm/mmu_context.h
@@ -3,6 +3,10 @@
#include <asm/desc.h>
#include <linux/atomic.h>
+#include <linux/mm_types.h>
+
+#include <trace/events/tlb.h>
+
#include <asm/pgalloc.h>
#include <asm/tlbflush.h>
#include <asm/paravirt.h>
@@ -44,6 +48,7 @@
/* Re-load page tables */
load_cr3(next->pgd);
+ trace_tlb_flush(TLB_FLUSH_ON_TASK_SWITCH, TLB_FLUSH_ALL);
/* Stop flush ipis for the previous mm */
cpumask_clear_cpu(cpu, mm_cpumask(prev));
@@ -71,6 +76,7 @@
* to make sure to use no freed page tables.
*/
load_cr3(next->pgd);
+ trace_tlb_flush(TLB_FLUSH_ON_TASK_SWITCH, TLB_FLUSH_ALL);
load_LDT_nolock(&next->context);
}
}
diff --git a/arch/x86/mm/init.c b/arch/x86/mm/init.c
index f971306..66dba36 100644
--- a/arch/x86/mm/init.c
+++ b/arch/x86/mm/init.c
@@ -18,6 +18,13 @@
#include <asm/dma.h> /* for MAX_DMA_PFN */
#include <asm/microcode.h>
+/*
+ * We need to define the tracepoints somewhere, and tlb.c
+ * is only compied when SMP=y.
+ */
+#define CREATE_TRACE_POINTS
+#include <trace/events/tlb.h>
+
#include "mm_internal.h"
static unsigned long __initdata pgt_buf_start;
diff --git a/arch/x86/mm/tlb.c b/arch/x86/mm/tlb.c
index add5a0f..6f00ecb 100644
--- a/arch/x86/mm/tlb.c
+++ b/arch/x86/mm/tlb.c
@@ -49,6 +49,7 @@
if (cpumask_test_cpu(cpu, mm_cpumask(active_mm))) {
cpumask_clear_cpu(cpu, mm_cpumask(active_mm));
load_cr3(swapper_pg_dir);
+ trace_tlb_flush(TLB_FLUSH_ON_TASK_SWITCH, TLB_FLUSH_ALL);
}
}
EXPORT_SYMBOL_GPL(leave_mm);
@@ -107,15 +108,19 @@
count_vm_tlb_event(NR_TLB_REMOTE_FLUSH_RECEIVED);
if (this_cpu_read(cpu_tlbstate.state) == TLBSTATE_OK) {
- if (f->flush_end == TLB_FLUSH_ALL)
+ if (f->flush_end == TLB_FLUSH_ALL) {
local_flush_tlb();
- else {
+ trace_tlb_flush(TLB_REMOTE_SHOOTDOWN, TLB_FLUSH_ALL);
+ } else {
unsigned long addr;
+ unsigned long nr_pages =
+ f->flush_end - f->flush_start / PAGE_SIZE;
addr = f->flush_start;
while (addr < f->flush_end) {
__flush_tlb_single(addr);
addr += PAGE_SIZE;
}
+ trace_tlb_flush(TLB_REMOTE_SHOOTDOWN, nr_pages);
}
} else
leave_mm(smp_processor_id());
@@ -153,6 +158,7 @@
count_vm_tlb_event(NR_TLB_LOCAL_FLUSH_ALL);
local_flush_tlb();
+ trace_tlb_flush(TLB_LOCAL_SHOOTDOWN, TLB_FLUSH_ALL);
if (cpumask_any_but(mm_cpumask(mm), smp_processor_id()) < nr_cpu_ids)
flush_tlb_others(mm_cpumask(mm), mm, 0UL, TLB_FLUSH_ALL);
preempt_enable();
@@ -191,6 +197,7 @@
__flush_tlb_single(addr);
}
}
+ trace_tlb_flush(TLB_LOCAL_MM_SHOOTDOWN, base_pages_to_flush);
out:
if (base_pages_to_flush == TLB_FLUSH_ALL) {
start = 0UL;
diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
index 96c5750..796deac 100644
--- a/include/linux/mm_types.h
+++ b/include/linux/mm_types.h
@@ -516,4 +516,12 @@
struct page **pages;
};
+enum tlb_flush_reason {
+ TLB_FLUSH_ON_TASK_SWITCH,
+ TLB_REMOTE_SHOOTDOWN,
+ TLB_LOCAL_SHOOTDOWN,
+ TLB_LOCAL_MM_SHOOTDOWN,
+ NR_TLB_FLUSH_REASONS,
+};
+
#endif /* _LINUX_MM_TYPES_H */
diff --git a/include/trace/events/tlb.h b/include/trace/events/tlb.h
new file mode 100644
index 0000000..13391d2
--- /dev/null
+++ b/include/trace/events/tlb.h
@@ -0,0 +1,40 @@
+#undef TRACE_SYSTEM
+#define TRACE_SYSTEM tlb
+
+#if !defined(_TRACE_TLB_H) || defined(TRACE_HEADER_MULTI_READ)
+#define _TRACE_TLB_H
+
+#include <linux/mm_types.h>
+#include <linux/tracepoint.h>
+
+#define TLB_FLUSH_REASON \
+ { TLB_FLUSH_ON_TASK_SWITCH, "flush on task switch" }, \
+ { TLB_REMOTE_SHOOTDOWN, "remote shootdown" }, \
+ { TLB_LOCAL_SHOOTDOWN, "local shootdown" }, \
+ { TLB_LOCAL_MM_SHOOTDOWN, "local mm shootdown" }
+
+TRACE_EVENT(tlb_flush,
+
+ TP_PROTO(int reason, unsigned long pages),
+ TP_ARGS(reason, pages),
+
+ TP_STRUCT__entry(
+ __field( int, reason)
+ __field(unsigned long, pages)
+ ),
+
+ TP_fast_assign(
+ __entry->reason = reason;
+ __entry->pages = pages;
+ ),
+
+ TP_printk("pages:%ld reason:%s (%d)",
+ __entry->pages,
+ __print_symbolic(__entry->reason, TLB_FLUSH_REASON),
+ __entry->reason)
+);
+
+#endif /* _TRACE_TLB_H */
+
+/* This part must be outside protection */
+#include <trace/define_trace.h>