Boosting your Kernel on Gentoo

Everybody knows that Gentoo is a performance-architeture-oriented Linux. You can optimize your entire system changing the compiler (gcc) flags to attend the hardware specificities.

Example: I have a Sony VAIO with Intel Core 2 Duo processor, then I can use this flags on my make.conf (I unmasked sys-devel/gcc to use gcc-4.3.3 that have native support to core2 technology)

CFLAGS="-O3 -march=core2 -pipe -fomit-frame-pointer -mfpmath=sse -mmmx -msse -msse2 -msse3 -mssse3"

Then, all binaries in your system will be optimized…but and the kernel ???

Well, when you compile the kernel it uses itself compiler flags. And how to optimize it ?

Good news to you…If you have a Intel processor and use Gentoo Linux in your machine you are a lucky man. You must know the LinuxDNA project. The idea of the project is optimize the kernel to Intel architecture using the icc (Intel Compiler).

Currently, I’m working on Gentoo ebuild to linuxdna package. You’ll have more news about it soon…

Listing Shared Memory Segments in C

In this week I had to write a little code to remove all IPC Shared Memory segments that were created by one process.

I had already done it on Linux and *BSD systems, but never on (Open)Solaris. Then, I tried to search (googling) some method to do it but without successful.

Linux and *BSD’s have a syscall named sysctl() to interface it, but sunos kernel has not.

Well, after some minutes breaking my brain, I discover a syscall easiest to use than sysctl…look the code below:

#include <stdlib.h>
#include <sys/types.h>
#include <sys/ipc.h>
#include <sys/shm.h>
void show_shm (void)
{
  int i;
  int     *buf;
  uint_t  nids;
  uint_t  pnids;
  for (;;)
  {
    if (shmids(buf, nids, &pnids) != 0)
      exit(1);
    if (pnids <= nids)
      break;
    buf = realloc(buf, (nids = pnids) * sizeof (int));
  }
  for (i = 0; i < pnids; i++)
    printf ("%dn", buf[i]);
}