The ministry of strange syscalls

My favorite syscall today:

$ man 2 readahead
"readahead() populates the page cache with data from a file so that subsequent reads from that file will not block on disk I/O."

I don't really know when should I use that, but it sounds cool. Just an implementation of prefetching on yet another layer. Wait a moment...

"readahead() blocks until the specified data has been read. "

I'm lost. If it blocks, why not to just use read(2)?


Second syscall:
$ man 2 madvise
"The madvise() system call advises the kernel about how to handle paging input/output in the address range beginning at address start and with size length bytes"
"The kernel is free to ignore the advice."

I don't get when I should use it.


And the last one:
$ man 2 mincore
"mincore() returns a vector that indicates whether pages of the calling process’s virtual memory are resident in core (RAM), and so will not cause a disk access (page fault) if referenced."

Cool, I can check if my memory page is in swap. I doubt it can help me in anything. If I don't want my pages to be in swap I'll just use mlock(2)...


Probably there are dozens of strange syscalls out there!

GIT is ahead of SVN!

Git is the most popular DVCS right now. Google trends confirms that:



But the interesting fact is that Git is for the first time ahead of its grandpa Svn:


Though it's worrying that CVS is still alive, it should be dead ten years ago. Hopefully we can see a process of slow death, the end is inevitable: