On 4/9/15 4:34 PM, David Miller wrote:
Have you ever used system call tracing on sparc? It does not work for
2.6.39 or 4.0; wondering if it has ever worked. I see signs in
arch/sparc/kernel/syscalls.S for example that suggests it should have
at
one point.
To clarify I mean through perf. Using the tracing interface via
debugfs I can get the raw_syscall tracepoints, just not through perf.
Oh, I've never tried to use that.
Only the usual syscall tracing faciltiies via ptrace() that programs
like strace make use of.
strace works fine, but the overhead of ptrace limits its use for
performance analysis. The entries in the trace facility are not user
friendly:
sshd-14987 [008] 25489.727139: sys_enter: NR 93 (b, 100001c8f10,
100001c8ef0, 0, 0, 0)
sshd-14987 [008] 25489.727141: sys_exit: NR 93 = 93
sshd-14987 [008] 25489.727143: sys_enter: NR 103 (1, 7feff9d8bb8,
7feff9d8c38, 8, fffffc01017d8d4c, 7feff9d8bb8)
sshd-14987 [008] 25489.727144: sys_exit: NR 103 = 103
The point of perf-trace is user friendly output (well, not user friendly
with line wrapping):
1.200 ( 0.023 ms): ls/13344 write(fd: 1, buf: 0x7f023781f000,
count: 90 ) = 90
1.226 ( 0.022 ms): ls/13344 write(fd: 1, buf: 0x7f023781f000,
count: 81 ) = 81
and the low overhead means you can use it to get stats to analyze
performance problems.
I'll ping Frederic and Steve for ideas on where to look.
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