Re: Sta.li critical performance question (WAS [dev] obase - Sta.li moving forward?)

From: Strake <strake888_AT_gmail.com>
Date: Fri, 8 Jun 2012 09:23:16 -0500

On 08/06/2012, Ethan Grammatikidis <eekee57_AT_fastmail.fm> wrote:
> On the linked page, Johan Petersson wrote:
>
>> It turns out, though, that system calls invoked via interrupts are
>> remarkably slow on the more recent members of the x86 processor
>> family. An int 0x80 system call can be as much as an order of
>> magnitude slower on a 2 GHz Pentium 4 than on an 850 MHz Pentium III.
>
> Will linux-vdso or linux-gate be properly used by a statically linked
> binary? Does it perhaps require /lib/ld-linux.so to link it in?
>
> I ask because I have some reason to believe syscall performance is
> important if you want to work in the unix way, and doubly so if you
> want a suckless system. Petersson here describes an order of magnitude
> difference in syscall performance. I'm not sure of my conclusion but
> it's something to keep an eye on, perhaps timing the piping of data in
> both static and conventional Linux systems on the same hardware.

On my x86 machine:

$ cat test.c
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>

int size = 1<<18;
int n = 1<<16;

void main () {
        char x[size];
        int ii;

        int ifd = open ("/dev/zero", O_RDONLY);
        int ofd = open ("/dev/null", O_WRONLY);

        for (ii = 0; ii < n; ii++) if (read (ifd, x, size) < 0 ||
write (ofd, x, size) < 0) exit (1);
}
$ ls -l $(which cc)
lrwxrwxrwx 1 root root 3 May 7 01:19 /usr/bin/cc -> gcc
$ cc test.c && ldd a.out
        linux-vdso.so.1 => (0x00007fffbfbff000)
        libc.so.6 => /lib/libc.so.6 (0x00007faf905f7000)
        /lib/ld-linux-x86-64.so.2 (0x00007faf90998000)
$ time ./a.out
./a.out 0.01s user 3.13s system 99% cpu 3.144 total
$ cc -static test.c && ldd a.out
        not a dynamic executable
$ time ./a.out
./a.out 0.00s user 3.14s system 100% cpu 3.145 total

No worries, it seems.

Cheers,
strake
Received on Fri Jun 08 2012 - 16:23:16 CEST