Hi Mel:

I've been looking into the vmscan:tracing you added for 2.6.36_rc1. I
also backported into 2.6.34 which is the kernel we are currently
working on. However, I seems can not get it fully functional. Are you
aware of any changes on the kernel tracing ABI which could cause that
?

Here is how I reproduce it and I also attached the
postprocess/trace-vmscan-postprocess.pl I patched.

# mount -t debugfs nodev /sys/kernel/debug/

# for i in `find /sys/kernel/debug/tracing/events -name "enable" |
grep mm_`; do echo 1 > $i; done

run a process with pid==30196

# echo 'common_pid == 30196' > /sys/kernel/debug/tracing/events/vmscan/filter

# cat /sys/kernel/debug/tracing/events/vmscan/filter
common_pid == 30196

# ./trace-vmscan-postprocess.pl < /sys/kernel/debug/tracing/trace_pipe
WARNING: Event vmscan/mm_vmscan_lru_shrink_inactive format string not found
WARNING: Event vmscan/mm_vmscan_lru_shrink_active format string not found
^CSIGINT received, report pending. Hit ctrl-c again to exit

Reclaim latencies expressed as order-latency_in_ms

Process          Direct     Wokeup      Pages      Pages    Pages
Time
details           Rclms     Kswapd    Scanned    Sync-IO ASync-IO
Stalled

Kswapd           Kswapd      Order      Pages      Pages    Pages
Instance        Wakeups  Re-wakeup    Scanned    Sync-IO ASync-IO

Summary
Direct reclaims:     			
Direct reclaim pages scanned:		
Direct reclaim write file sync I/O:	
Direct reclaim write anon sync I/O:	
Direct reclaim write file async I/O:	
Direct reclaim write anon async I/O:	
Wake kswapd requests:			
Time stalled direct reclaim: 		0.00 seconds

Kswapd wakeups:				
Kswapd pages scanned:			
Kswapd reclaim write file sync I/O:	
Kswapd reclaim write anon sync I/O:	
Kswapd reclaim write file async I/O:	
Kswapd reclaim write anon async I/O:	
Time kswapd awake:			0.00 seconds

So it didn't give me any output. However, if I turn off the filter for
vmscan, it did give me some data but with random processes on the
system.

The same set of tests works for trace-pagealloc-postprocess.pl though

# cat /sys/kernel/debug/tracing/events/kmem/filter
common_pid == 30196

# ./trace-pagealloc-postprocess.pl < /sys/kernel/debug/tracing/trace_pipe

Process           Pages      Pages      Pages    Pages       PCPU
PCPU     PCPU   Fragment Fragment  MigType Fragment Fragment  Unknown
details          allocd     allocd      freed    freed      pages
drains  refills   Fallback  Causing  Changed   Severe Moderate
                        under lock     direct  pagevec      drain
-30196             2871       2917          0        0          0
  0      439         32       32        0       32        0        0
ddtest-30196       4560       4328          0        0          0
  0      639         26       26        1       25        1        0


Thanks

--Ying