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Subject[PATCH] mm, vmscan, tracing: Use pointer to reclaim_stat struct in trace event

The trace event trace_mm_vmscan_lru_shrink_inactive() currently has 12
parameters! Seven of them are from the reclaim_stat structure. This
structure is currently local to mm/vmscan.c. By moving it to the global
vmstat.h header, we can also reference it from the vmscan tracepoints. In
moving it, it brings down the overhead of passing so many arguments to the
trace event. In the future, we may limit the number of arguments that a
trace event may pass (ideally just 6, but more realistically it may be 8).

Before this patch, the code to call the trace event is this:

0f 83 aa fe ff ff jae ffffffff811e6261 <shrink_inactive_list+0x1e1>
48 8b 45 a0 mov -0x60(%rbp),%rax
45 8b 64 24 20 mov 0x20(%r12),%r12d
44 8b 6d d4 mov -0x2c(%rbp),%r13d
8b 4d d0 mov -0x30(%rbp),%ecx
44 8b 75 cc mov -0x34(%rbp),%r14d
44 8b 7d c8 mov -0x38(%rbp),%r15d
48 89 45 90 mov %rax,-0x70(%rbp)
8b 83 b8 fe ff ff mov -0x148(%rbx),%eax
8b 55 c0 mov -0x40(%rbp),%edx
8b 7d c4 mov -0x3c(%rbp),%edi
8b 75 b8 mov -0x48(%rbp),%esi
89 45 80 mov %eax,-0x80(%rbp)
65 ff 05 e4 f7 e2 7e incl %gs:0x7ee2f7e4(%rip) # 15bd0 <__preempt_count>
48 8b 05 75 5b 13 01 mov 0x1135b75(%rip),%rax # ffffffff8231bf68 <__tracepoint_mm_vmscan_lru_shrink_inactive+0x28>
48 85 c0 test %rax,%rax
74 72 je ffffffff811e646a <shrink_inactive_list+0x3ea>
48 89 c3 mov %rax,%rbx
4c 8b 10 mov (%rax),%r10
89 f8 mov %edi,%eax
48 89 85 68 ff ff ff mov %rax,-0x98(%rbp)
89 f0 mov %esi,%eax
48 89 85 60 ff ff ff mov %rax,-0xa0(%rbp)
89 c8 mov %ecx,%eax
48 89 85 78 ff ff ff mov %rax,-0x88(%rbp)
89 d0 mov %edx,%eax
48 89 85 70 ff ff ff mov %rax,-0x90(%rbp)
8b 45 8c mov -0x74(%rbp),%eax
48 8b 7b 08 mov 0x8(%rbx),%rdi
48 83 c3 18 add $0x18,%rbx
50 push %rax
41 54 push %r12
41 55 push %r13
ff b5 78 ff ff ff pushq -0x88(%rbp)
41 56 push %r14
41 57 push %r15
ff b5 70 ff ff ff pushq -0x90(%rbp)
4c 8b 8d 68 ff ff ff mov -0x98(%rbp),%r9
4c 8b 85 60 ff ff ff mov -0xa0(%rbp),%r8
48 8b 4d 98 mov -0x68(%rbp),%rcx
48 8b 55 90 mov -0x70(%rbp),%rdx
8b 75 80 mov -0x80(%rbp),%esi
41 ff d2 callq *%r10

After the patch:

0f 83 a8 fe ff ff jae ffffffff811e626d <shrink_inactive_list+0x1cd>
8b 9b b8 fe ff ff mov -0x148(%rbx),%ebx
45 8b 64 24 20 mov 0x20(%r12),%r12d
4c 8b 6d a0 mov -0x60(%rbp),%r13
65 ff 05 f5 f7 e2 7e incl %gs:0x7ee2f7f5(%rip) # 15bd0 <__preempt_count>
4c 8b 35 86 5b 13 01 mov 0x1135b86(%rip),%r14 # ffffffff8231bf68 <__tracepoint_mm_vmscan_lru_shrink_inactive+0x28>
4d 85 f6 test %r14,%r14
74 2a je ffffffff811e6411 <shrink_inactive_list+0x371>
49 8b 06 mov (%r14),%rax
8b 4d 8c mov -0x74(%rbp),%ecx
49 8b 7e 08 mov 0x8(%r14),%rdi
49 83 c6 18 add $0x18,%r14
4c 89 ea mov %r13,%rdx
45 89 e1 mov %r12d,%r9d
4c 8d 45 b8 lea -0x48(%rbp),%r8
89 de mov %ebx,%esi
51 push %rcx
48 8b 4d 98 mov -0x68(%rbp),%rcx
ff d0 callq *%rax

Link: http://lkml.kernel.org/r/2559d7cb-ec60-1200-2362-04fa34fd02bb@fb.com

Reported-by: Alexei Starovoitov <ast@fb.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
---
include/linux/vmstat.h | 11 +++++++++++
include/trace/events/vmscan.h | 24 +++++++++---------------
mm/vmscan.c | 18 +-----------------
3 files changed, 21 insertions(+), 32 deletions(-)

diff --git a/include/linux/vmstat.h b/include/linux/vmstat.h
index a4c2317d8b9f..f25cef84b41d 100644
--- a/include/linux/vmstat.h
+++ b/include/linux/vmstat.h
@@ -20,6 +20,17 @@ extern int sysctl_vm_numa_stat_handler(struct ctl_table *table,
int write, void __user *buffer, size_t *length, loff_t *ppos);
#endif

+struct reclaim_stat {
+ unsigned nr_dirty;
+ unsigned nr_unqueued_dirty;
+ unsigned nr_congested;
+ unsigned nr_writeback;
+ unsigned nr_immediate;
+ unsigned nr_activate;
+ unsigned nr_ref_keep;
+ unsigned nr_unmap_fail;
+};
+
#ifdef CONFIG_VM_EVENT_COUNTERS
/*
* Light weight per cpu counter implementation.
diff --git a/include/trace/events/vmscan.h b/include/trace/events/vmscan.h
index e0b8b9173e1c..5a7435296d89 100644
--- a/include/trace/events/vmscan.h
+++ b/include/trace/events/vmscan.h
@@ -343,15 +343,9 @@ TRACE_EVENT(mm_vmscan_lru_shrink_inactive,

TP_PROTO(int nid,
unsigned long nr_scanned, unsigned long nr_reclaimed,
- unsigned long nr_dirty, unsigned long nr_writeback,
- unsigned long nr_congested, unsigned long nr_immediate,
- unsigned long nr_activate, unsigned long nr_ref_keep,
- unsigned long nr_unmap_fail,
- int priority, int file),
+ struct reclaim_stat *stat, int priority, int file),

- TP_ARGS(nid, nr_scanned, nr_reclaimed, nr_dirty, nr_writeback,
- nr_congested, nr_immediate, nr_activate, nr_ref_keep,
- nr_unmap_fail, priority, file),
+ TP_ARGS(nid, nr_scanned, nr_reclaimed, stat, priority, file),

TP_STRUCT__entry(
__field(int, nid)
@@ -372,13 +366,13 @@ TRACE_EVENT(mm_vmscan_lru_shrink_inactive,
__entry->nid = nid;
__entry->nr_scanned = nr_scanned;
__entry->nr_reclaimed = nr_reclaimed;
- __entry->nr_dirty = nr_dirty;
- __entry->nr_writeback = nr_writeback;
- __entry->nr_congested = nr_congested;
- __entry->nr_immediate = nr_immediate;
- __entry->nr_activate = nr_activate;
- __entry->nr_ref_keep = nr_ref_keep;
- __entry->nr_unmap_fail = nr_unmap_fail;
+ __entry->nr_dirty = stat->nr_dirty;
+ __entry->nr_writeback = stat->nr_writeback;
+ __entry->nr_congested = stat->nr_congested;
+ __entry->nr_immediate = stat->nr_immediate;
+ __entry->nr_activate = stat->nr_activate;
+ __entry->nr_ref_keep = stat->nr_ref_keep;
+ __entry->nr_unmap_fail = stat->nr_unmap_fail;
__entry->priority = priority;
__entry->reclaim_flags = trace_shrink_flags(file);
),
diff --git a/mm/vmscan.c b/mm/vmscan.c
index bee53495a829..aaeb86642095 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -865,17 +865,6 @@ static void page_check_dirty_writeback(struct page *page,
mapping->a_ops->is_dirty_writeback(page, dirty, writeback);
}

-struct reclaim_stat {
- unsigned nr_dirty;
- unsigned nr_unqueued_dirty;
- unsigned nr_congested;
- unsigned nr_writeback;
- unsigned nr_immediate;
- unsigned nr_activate;
- unsigned nr_ref_keep;
- unsigned nr_unmap_fail;
-};
-
/*
* shrink_page_list() returns the number of reclaimed pages
*/
@@ -1828,12 +1817,7 @@ shrink_inactive_list(unsigned long nr_to_scan, struct lruvec *lruvec,
wait_iff_congested(pgdat, BLK_RW_ASYNC, HZ/10);

trace_mm_vmscan_lru_shrink_inactive(pgdat->node_id,
- nr_scanned, nr_reclaimed,
- stat.nr_dirty, stat.nr_writeback,
- stat.nr_congested, stat.nr_immediate,
- stat.nr_activate, stat.nr_ref_keep,
- stat.nr_unmap_fail,
- sc->priority, file);
+ nr_scanned, nr_reclaimed, &stat, sc->priority, file);
return nr_reclaimed;
}

--
2.13.6
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