How can 0% + 0%+ 0%+ 0%+ 0%+ 0% = 100% ? looks like it just prints 100% all
the time and doesn't really add any total. All those zeros seem strange
unless your computer is so fast that every call takes so much less than a
microsecond that I can't be measured.
James
-Original Message-
From: fpc-pascal On Behalf Of
Michael Van Canneyt
Sent: Monday, January 6, 2020 11:44 PM
To: Vojtěch Čihák via fpc-pascal
Subject: Re: [fpc-pascal] "Hello world" syscalls
On Tue, 7 Jan 2020, Vojtěch Čihák via fpc-pascal wrote:
> Hi,
>
> I found this article: https://drewdevault.com/2020/01/04/Slow.html
> but FPC is missing, so I wrote simple:
>
> program Project1;
> begin
> writeln('Hello world!');
> end.
>
> $ fpc -O3 -XX Project1.pas
>
> $ strace -C ./Project1
>
> % time seconds usecs/call calls errors syscall
> -- --- --- - -
> 30.83 0.37 37 1 readlink
> 25.83 0.31 8 4 ioctl
> 18.33 0.22 22 1 write
> 17.50 0.21 5 4 rt_sigaction
> 4.17 0.05 5 1 getrlimit
> 3.33 0.04 4 1 execve
> -- --- --- - -
> 100.00 0.000120 12 total
If I do the same, I get this:
% time seconds usecs/call callserrors syscall
-- --- --- - -
0.000.00 0 1 write
0.000.00 0 4 rt_sigaction
0.000.00 0 4 ioctl
0.000.00 0 1 execve
0.000.00 0 1 readlink
0.000.00 0 1 getrlimit
-- --- --- - -
100.000.0012 total
>
> It results in 30kB binary, 12 syscalls total, 6 unique. IMO appropriate.
Size of the binary is irrelevant.
> Has the fact that strings are managed types some relevance here?
No. And in your example, there are no managed strings, since shortstring
will be used.
The rtl (system unit in particular) just takes some setting up.
* execve is normal, you'll always have it.
* Readlink is to determine paramstr(0).
* rt_sigaction is to set up runtime errors (signal handling).
* getrlimit is to set up stack/heap checking.
* ioctl() is to determine whether stdio file descriptors are terminals or
not.
These are all one-time calls. No amount of optimization will reduce this.
The real call: write(), happens only once, as it should be.
So these numbers are perfectly normal.
In the lifetime of any real application, they're negligable.
Michael.
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