From: Avery Pennarun <apenwarr@gmail.com>
Date: Fri, 16 May 2008 14:56:35 GMT
Subject: Re: [PATCH] mailsplit and mailinfo: gracefully handle NUL characters
Message-ID: <32541b130805160756h5a8fc4d7x313f9bfde4760568@mail.gmail.com>
In-Reply-To: <alpine.DEB.1.00.0805161529390.30431@racer>

On 5/16/08, Johannes Schindelin <Johannes.Schindelin@gmx.de> wrote:
> Hmpf.  I hoped to get more definitive information here.  Especially given
>  that fgetc() is nothing more than a glorified fread() into a buffer, and
>  then access the buffer.
>
>  Well, at least you kind of pointed me to the _unlocked() function family.

Point taken.

/tmp $ for d in test1 test2 test3 test3u; do echo -n "$d: ";
/usr/bin/time ./$d </dev/zero; done
test1: 0.09user 0.05system 0:00.14elapsed 94%CPU
test2: 2.50user 0.05system 0:02.54elapsed 100%CPU
test3: 2.48user 0.06system 0:02.53elapsed 100%CPU
test3u: 1.05user 0.05system 0:01.10elapsed 99%CPU

fread is about 18x faster than fgetc().  getc() is the same speed as
fgetc().  getc_unlocked() is definitely faster than getc, but still at
least 7x slower than fread().

And if you think *that* sucks, you should try "c << cin" in C++ :)

Source code below.

Have fun,

Avery


=== test1.c ===
#include <stdio.h>

int main()
{
    char buf[1024];
    int i;
    for (i = 0; i < 102400; i++)
        fread(buf, 1, sizeof(buf), stdin);
}

=== test2.c ===
#include <stdio.h>

int main()
{
    int i;
    for (i = 0; i < 1024*102400; i++)
        fgetc(stdin);
}

=== test3.c ===
#include <stdio.h>

int main()
{
    int i;
    for (i = 0; i < 1024*102400; i++)
        getc(stdin);
}

=== test3u.c ===
#include <stdio.h>

int main()
{
    int i;
    for (i = 0; i < 1024*102400; i++)
        getc_unlocked(stdin);
}