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Date:   Thu, 22 Mar 2018 12:10:03 -0400
From:   Steven Rostedt <rostedt@goodmis.org>
To:     LKML <linux-kernel@vger.kernel.org>, linux-mm@kvack.org
Cc:     Michal Hocko <mhocko@suse.com>, Mel Gorman <mgorman@suse.de>,
        Vlastimil Babka <vbabka@suse.cz>,
        Andrew Morton <akpm@linux-foundation.org>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Alexei Starovoitov <ast@fb.com>
Subject: [PATCH] mm, vmscan, tracing: Use pointer to reclaim_stat struct in
 trace event
Message-ID: <20180322121003.4177af15@gandalf.local.home>
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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