[patch 026/158] mm: emit tracepoint when RSS changes

* [patch 026/158] mm: emit tracepoint when RSS changes
@ 2019-12-01  1:50 akpm
  2019-12-02 17:14 ` Steven Rostedt
  0 siblings, 1 reply; 12+ messages in thread
From: akpm @ 2019-12-01  1:50 UTC (permalink / raw)
  To: akpm, aneesh.kumar, carmenjackson, dan.j.williams, dancol,
	jglisse, joel, linux-mm, mayankgupta, mhocko, minchan,
	mm-commits, rcampbell, rostedt, timmurray, torvalds, vbabka,
	willy

From: "Joel Fernandes (Google)" <joel@joelfernandes.org>
Subject: mm: emit tracepoint when RSS changes

Useful to track how RSS is changing per TGID to detect spikes in RSS and
memory hogs.  Several Android teams have been using this patch in various
kernel trees for half a year now.  Many reported to me it is really useful
so I'm posting it upstream.

Initial patch developed by Tim Murray.  Changes I made from original
patch: o Prevent any additional space consumed by mm_struct.

Regarding the fact that the RSS may change too often thus flooding the
traces - note that, there is some "hysterisis" with this already.  That is
- We update the counter only if we receive 64 page faults due to
SPLIT_RSS_ACCOUNTING.  However, during zapping or copying of pte range,
the RSS is updated immediately which can become noisy/flooding.  In a
previous discussion, we agreed that BPF or ftrace can be used to rate
limit the signal if this becomes an issue.

Also note that I added wrappers to trace_rss_stat to prevent compiler
errors where linux/mm.h is included from tracing code, causing errors such
as:

  CC      kernel/trace/power-traces.o
In file included from ./include/trace/define_trace.h:102,
                 from ./include/trace/events/kmem.h:342,
                 from ./include/linux/mm.h:31,
                 from ./include/linux/ring_buffer.h:5,
                 from ./include/linux/trace_events.h:6,
                 from ./include/trace/events/power.h:12,
                 from kernel/trace/power-traces.c:15:
./include/trace/trace_events.h:113:22: error: field `ent' has incomplete type
   struct trace_entry ent;    \

Link: http://lore.kernel.org/r/20190903200905.198642-1-joel@joelfernandes.org
Link: http://lkml.kernel.org/r/20191001172817.234886-1-joel@joelfernandes.org
Co-developed-by: Tim Murray <timmurray@google.com>
Signed-off-by: Tim Murray <timmurray@google.com>
Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Carmen Jackson <carmenjackson@google.com>
Cc: Mayank Gupta <mayankgupta@google.com>
Cc: Daniel Colascione <dancol@google.com>
Cc: Steven Rostedt (VMware) <rostedt@goodmis.org>
Cc: Minchan Kim <minchan@kernel.org>
Cc: "Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Jerome Glisse <jglisse@redhat.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Ralph Campbell <rcampbell@nvidia.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 include/linux/mm.h          |   14 +++++++++++---
 include/trace/events/kmem.h |   21 +++++++++++++++++++++
 mm/memory.c                 |    6 ++++++
 3 files changed, 38 insertions(+), 3 deletions(-)

--- a/include/linux/mm.h~mm-emit-tracepoint-when-rss-changes
+++ a/include/linux/mm.h
@@ -1643,19 +1643,27 @@ static inline unsigned long get_mm_count
 	return (unsigned long)val;
 }
 
+void mm_trace_rss_stat(int member, long count);
+
 static inline void add_mm_counter(struct mm_struct *mm, int member, long value)
 {
-	atomic_long_add(value, &mm->rss_stat.count[member]);
+	long count = atomic_long_add_return(value, &mm->rss_stat.count[member]);
+
+	mm_trace_rss_stat(member, count);
 }
 
 static inline void inc_mm_counter(struct mm_struct *mm, int member)
 {
-	atomic_long_inc(&mm->rss_stat.count[member]);
+	long count = atomic_long_inc_return(&mm->rss_stat.count[member]);
+
+	mm_trace_rss_stat(member, count);
 }
 
 static inline void dec_mm_counter(struct mm_struct *mm, int member)
 {
-	atomic_long_dec(&mm->rss_stat.count[member]);
+	long count = atomic_long_dec_return(&mm->rss_stat.count[member]);
+
+	mm_trace_rss_stat(member, count);
 }
 
 /* Optimized variant when page is already known not to be PageAnon */
--- a/include/trace/events/kmem.h~mm-emit-tracepoint-when-rss-changes
+++ a/include/trace/events/kmem.h
@@ -316,6 +316,27 @@ TRACE_EVENT(mm_page_alloc_extfrag,
 		__entry->change_ownership)
 );
 
+TRACE_EVENT(rss_stat,
+
+	TP_PROTO(int member,
+		long count),
+
+	TP_ARGS(member, count),
+
+	TP_STRUCT__entry(
+		__field(int, member)
+		__field(long, size)
+	),
+
+	TP_fast_assign(
+		__entry->member = member;
+		__entry->size = (count << PAGE_SHIFT);
+	),
+
+	TP_printk("member=%d size=%ldB",
+		__entry->member,
+		__entry->size)
+	);
 #endif /* _TRACE_KMEM_H */
 
 /* This part must be outside protection */
--- a/mm/memory.c~mm-emit-tracepoint-when-rss-changes
+++ a/mm/memory.c
@@ -72,6 +72,8 @@
 #include <linux/oom.h>
 #include <linux/numa.h>
 
+#include <trace/events/kmem.h>
+
 #include <asm/io.h>
 #include <asm/mmu_context.h>
 #include <asm/pgalloc.h>
@@ -152,6 +154,10 @@ static int __init init_zero_pfn(void)
 }
 core_initcall(init_zero_pfn);
 
+void mm_trace_rss_stat(int member, long count)
+{
+	trace_rss_stat(member, count);
+}
 
 #if defined(SPLIT_RSS_COUNTING)
 
_


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