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SubjectRe: [RFC PATCH 0/7] perf: 'live mode'
On Wed, Mar 03, 2010 at 01:05:22AM -0600, Tom Zanussi wrote:
> Currently, a perf session entails two steps: first 'perf record' or
> 'perf trace record' records the perf data to disk, then 'perf report'
> or 'perf trace report' reads the saved data from disk and reports the
> results.
>
> This experimental patchset makes some changes to perf that instead
> allow the perf data to be piped directly from the record step to the
> report step, without ever touching the disk.
>
> This is especially useful for 'perf trace' - adding this capability
> means that the trace scripts are no longer relegated to simple
> post-processing, but can be run in a continuous 'live mode', forever
> processing the event stream and e.g. periodically dumping current
> results, essentially becoming special-purpose 'top' applications, or
> continuously scanning the event stream for arbitrarily complex
> conditions to flag, etc...
>
> Being able to feed the event stream over a pipe also makes it possible
> to do things like trace over the network using e.g. netcat.
>
> It turns out that perf is pretty close to being able to do this
> already, with the exception of the header data; most of the work of
> this patchset deals with changing that. It does so in a mainly
> additive way: it doesn't make any changes to the existing disk format
> or normal disk-mode processing, just adds special treatment for the
> cases when 'perf [trace] record' records to stdout or 'perf [trace]
> report reads from stdin.
>
> Here are some quick examples. Basically using '-' as the filename to
> the -o and -i options send/read the data from stdout/stdin:
>
> Here's a simple 'perf record' | 'perf report' run:
>
> root@tropicana:~# perf record -o - -c 1 -f -a -M -R -e raw_syscalls:sys_enter | perf report -i -
> ^C# Samples: 120234
> #
> # Overhead Command Shared Object Symbol
> # ........ ............... ......................... ......
> #
> 98.65% perf libpthread-2.8.90.so [.] __read
> 0.46% perf libpthread-2.8.90.so [.] __write_nocancel
> 0.32% perf libpthread-2.8.90.so [.] __open_nocancel
> 0.29% perf libpthread-2.8.90.so [.] __libc_close
> 0.07% perf libc-2.8.90.so [.] 0x000000000a4b15
> 0.03% perf libc-2.8.90.so [.] __fxstat64
> 0.03% perf libc-2.8.90.so [.] __open
> 0.03% perf libc-2.8.90.so [.] close
> 0.02% Xorg libc-2.8.90.so [.] __select
> 0.01% Xorg libpthread-2.8.90.so [.] __read
> 0.01% perf libpthread-2.8.90.so [.] __libc_lseek
> 0.01% Xorg libc-2.8.90.so [.] setitimer
> 0.01% perf libc-2.8.90.so [.] __xstat64
> 0.01% firefox libpthread-2.8.90.so [.] __read
> 0.00% perf libc-2.8.90.so [.] llseek
> 0.00% Xorg libpthread-2.8.90.so [.] __restore_rt
> 0.00% Xorg libc-2.8.90.so [.] sigprocmask
> 0.00% Xorg libc-2.8.90.so [.] __poll
> 0.00% wterm libc-2.8.90.so [.] __read
> 0.00% gnome-screensav libpthread-2.8.90.so [.] __read
> 0.00% firefox libc-2.8.90.so [.] __poll
> 0.00% Xorg libc-2.8.90.so [.] writev
> 0.00% gnome-settings- libpthread-2.8.90.so [.] __read
> 0.00% wterm libc-2.8.90.so [.] __select
> 0.00% perf libc-2.8.90.so [.] statfs
> 0.00% mysqld libc-2.8.90.so [.] __select
> 0.00% firefox libpthread-2.8.90.so [.] __pthread_cond_timedwait
> 0.00% firefox libpthread-2.8.90.so [.] __lll_unlock_wake
> 0.00% firefox libpthread-2.8.90.so [.] 0x0000000000decb
> 0.00% firefox libc-2.8.90.so [.] __select
> 0.00% perf libc-2.8.90.so [.] getcwd
> 0.00% perf libc-2.8.90.so [.] mmap64
> 0.00% gnome-settings- libc-2.8.90.so [.] __poll
> 0.00% gnome-screensav libc-2.8.90.so [.] __poll
> 0.00% firefox libc-2.8.90.so [.] writev
> 0.00% apache2 libpthread-2.8.90.so [.] __waitpid
> 0.00% apache2 libc-2.8.90.so [.] __select
> #
> # (For a higher level overview, try: perf report --sort comm,dso)
> #
>
> Included in this patchset are a couple of 'top' scripts, rwtop and
> sctop, that are essentially just modifications of existing scripts.
> Basically the original scripts were modified to add a 5 second timer.
> In the handler for the timer, the current output summary is printed,
> and the state is cleared and begun anew, ad infinitum.
>
> Here are the new scripts as shown in the perf trace list:
>
> root@tropicana:~# perf trace -l
> List of available trace scripts:
> workqueue-stats workqueue stats (ins/exe/create/destroy)
> wakeup-latency system-wide min/max/avg wakeup latency
> rw-by-file <comm> r/w activity for a program, by file
> rwtop system-wide r/w top
> failed-syscalls [comm] system-wide failed syscalls
> rw-by-pid system-wide r/w activity
> syscall-counts-by-pid [comm] system-wide syscall counts, by pid
> failed-syscalls-by-pid [comm] system-wide failed syscalls, by pid
> sctop [comm] syscall top
> syscall-counts [comm] system-wide syscall counts
>
>
> And here's a few iterations of the output of the 'sctop' Python
> script:
>
> root@tropicana:~# perf trace record sctop | perf trace report sctop
> perf trace started with Python script /root/libexec/perf-core/scripts/python/sctop.py
>
> syscall events:
>
> event count
> ---------------------------------------- -----------
> 2 179
> 3 158
> 0 79
> 78 24
> 5 13
> 1 3
> 16 2
> 298 1
> 137 1
> 79 1
> 72 1
> 8 1
>
> syscall events:
>
> event count
> ---------------------------------------- -----------
> 0 659287
> 202 1995
> 1 812
> 2 246
> 3 224
> 78 56
> 12 51
> 5 23
> 23 22
> 8 18
> 7 18
> 4 9
> 38 6
> 61 5
> 254 4
> 20 2
> 16 2
> 137 1
> 15 1
> 14 1
> 9 1
>
> syscall events:
>
> event count
> ---------------------------------------- -----------
> 0 647178
> 202 1209
> 1 324
> 12 52
> 7 29
> 14 6
> 16 4
> 23 3
> 3 3
> 72 2
> 21 1
> 11 1
> 9 1
> 5 1
> 4 1
> 2 1
>
> .
> .
> .
>
> Obviously, it would be better to have a real top-like display for
> these rather than a continuously scrolling mode like this, and of
> course it will be much more useful once we get the syscall name
> injection events going (the column on the left shows syscall numbers
> only).
>



That's a very nice thing. I guess that we could make
the scripting API to provide something to write such top
like things.

Providing a simple dict must be enough, something organized like
this:

topdict = {
"colname" : [val1, val2, val3],
"col2name" : [val4, val5, val6]
}
Or may be a callback that returns a dict.



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