Date: Sun, 14 Dec 2025 23:18:32 -0800 From: Steve Kargl <kargls@comcast.net> To: Mark Millard <marklmi@yahoo.com>, freebsd-hackers <freebsd-hackers@freebsd.org> Subject: Re: profiling a user executable? Message-ID: <fe1f5702-fcd0-4fea-bf34-be070713abae@comcast.net> In-Reply-To: <12053856-4DE5-4B98-9309-028869BB5395@yahoo.com> References: <12053856-4DE5-4B98-9309-028869BB5395.ref@yahoo.com> <12053856-4DE5-4B98-9309-028869BB5395@yahoo.com>
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On 12/14/25 21:55, Mark Millard wrote:
> Steve Kargl <kargls_at_comcast.net> wrote on
> Date: Sat, 13 Dec 2025 20:12:12 UTC :
>
>> On 12/12/25 14:14, Ahmad Khalifa wrote:
>>> On Thu Dec 11, 2025 at 8:13 PM +0200, Steve Kargl wrote:
>>>> In the days of yore, one could add the '-pg' option to
>>>> the compilers options to generate profiling information,
>>>> which could be consumed by gprof(1).
>>>>
>>>> FreeBSD stopped shipping libc_p.a, libm_p.m, etc
>>>> (disabled in fe52b7f60ef4 and deleted in 3750ccefb8).
>>>> This breaks all lang/gcc* ports if one uses '-pg'. It is
>>>> not too difficult to fix lang/gcc* to avoid the missing
>>>> *_p.a files, but this seems to lead to invalid *.gmon files.
>>>> At least, for a Fortran application that I would like to
>>>> profile (compiled with gfortran), procedures in my libfoo_p.a,
>>>> appear in the profile, which I know with 100% certainty are
>>>> not referenced.
>>>>
>>>> So, how does one in modern FreeBSD, as mere normal user,
>>>> profile an executable? A google search suggests pmcstat(8)
>>>> may be of use, but all attempts to use it lead to a usage
>>>> message printed to the terminal. I'm simply trying to
>>>> determine where my code is spending all of its time.
>>>
>>> Just throwing in another option, you can use dtrace's profile-n probes.
>>>
>>
>> dtrace appears to be a useless for a mere user.
>>
>> % dtrace -n 'profile-99 /execname == "../../build/bin/tier -q"/ \
>
> As I remember, execname holds only the base name that had been given
> to exec for the current thread/process. Also, it is not a way to run
> a program. It is a way to select processes/threads that are running
> a known-base-name of interest. It is DTrace variable in specific
> probes, not all probes.
>
> As I remember, dtrace uses -c COMMAND notation to run the command
> and exit once that command completes.
>
> Trying to deal with paths is much more involved and can involve things
> like copyinstr(arg0) notation, arg0 being for the first argument to the
> probe as the example.
>
Unfortunately, dtrace requires root privilege, and so is
a non-starter.
I adapted your suggestions with pmcstat to my problem,
and it seems promising.
% pmcstat -O pmc.0 -P ex_ret_instr ../../build/bin/tier -q
% pmcstat -R pmc.0 -g
% gprof ../../build/bin/tier ex_ret_instr/tier.gmon | head -10 | tail -8
Each sample counts as 0.0078125 seconds.
% cumulative self self total
time seconds seconds calls ms/call ms/call name
36.68 13.15 13.15 13192 1.00 1.75 __spherem_MOD_sphere
23.06 21.41 8.27 __pnam_MOD_pna_dble
16.85 27.45 6.04 2045 2.95 3.00 __sjnm_MOD_sjn_dble
10.08 31.07 3.61 693 5.21 5.34 __synm_MOD_syn_dble
8.02 33.94 2.88 __sjnm_MOD_sjn_sngl
I know with 100% certainty that __sjnm_MOD_sjn_sngl is not
referenced in the code as I wrote it. I'll note the above
is similar to what 'gfortran -pg' produces.
% pmcstat -R pmc.0 -G zxc.graph
CONVERSION STATISTICS:
#exec/elf 1
#samples/total 67133
#samples/unknown-function 1775
#callchain/dubious-frames 17
% grep sjn_dble zxc.graph | wc -l
258
% grep sjn_sngl zxc.graph | wc -l
0
The callgraph shows that __sjnm_MOD_sjn_sngl is not used.
My working conclusion is that gprof is simply broken. I'm
still investigating what pmcstat can given me. Given the
attempt to convert to a gprof file, hopefully I can get
something like
% pmcstat -R pmc.0 [some option(s)]
cycles cycles/cal function
10000 90 __spherem_MOD_sphere
12345 191 __pnam_MOD_pna_dble
5433 400 __sjnm_MOD_sjn_dble
15000 1500 __synm_MOD_syn_dble
This would tell me which routine(s) to look into for
optimizations.
--
steve
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