Monetdb's Stethoscope is a profiling tool and has a list of trace options. In the following measured result, I get confused by some metrics.
What exactly is utime, cutime, stime and cstime? They seem to be CPU time in user and kernel space but why the 'start' state of a MAL instruction has such utime but the 'end' state does not have? And, what's its unit?
What's the unit of rss?
blk.reads blk.writes should be the speed of I/O in terms of block. Why some instructions have non-zero blk.reads or blk.writes but their rbytes (bytes read) and wbytes (bytes written) are zero?
This measurement is enabled by this trace option: +SatefiITcmrwbsy which is explained below the the document online. I am not quite sure about their meanings.
The trace options (default 'ISTest'):
S = monitor start of instruction profiling
a = aggregate clock ticks per instruction
e = event counter
f = module.function name
i = instruction counter
I = interpreter thread number
T = wall clock time
t = ticks in microseconds
c = cpu statistics (utime,ctime,stime,cstime)
m = memory resources as provided by OS
r = block reads
w = block writes
b = bytes read/written
s = MAL statement
y = MAL argument types
p = process statistics, e.g. page faults, context switches
u = user id
D = Generate dot file upon query start
F = Dataflow memory claims
The markers correlate with the Linux kernel profiling structure entries. See times(2) command
Similar remarks are for the io counts taken from rusage system calls. rbytes/wbytes are estimated systems of memory processed in each call.
layout is meant to be regular structure for ease of handling later on.