From: Corinna Vinschen <corinna-cygwin@cygwin.com>
To: cygwin@cygwin.com
Subject: Re: calloc speed difference
Date: Fri, 12 Jan 2018 14:33:00 -0000 [thread overview]
Message-ID: <20180112143339.GE24623@calimero.vinschen.de> (raw)
In-Reply-To: <46515148-9f8e-6eae-69f9-9bf20921097a@t-online.de>
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On Jan 12 15:06, Christian Franke wrote:
> Lee wrote:
> > Why is the cygwin gcc calloc so much slower than the
> > i686-w64-mingw32-gcc calloc?
> > 1:12 vs 0:11
> >
> > $cat calloc-test.c
> > #include <stdio.h>
> > #include <stdlib.h>
> > #define ALLOCATION_SIZE (100 * 1024 * 1024)
> > int main (int argc, char *argv[]) {
> > for (int i = 0; i < 10000; i++) {
> > void *temp = calloc(ALLOCATION_SIZE, 1);
> > if ( temp == NULL ) {
> > printf("drat! calloc returned NULL\n");
> > return 1;
> > }
> > free(temp);
> > }
> > return 0;
> > }
> >
>
> Could reproduce the difference on an older i7-2600K machine:
>
> Cygwin: ~20s
> MinGW: ~4s
>
> Timing [cm]alloc() calls without actually using the allocated memory might
> produce misleading results due to lazy page allocation and/or zero-filling.
>
> MinGW binaries use calloc() from msvcrt.dll. This calloc() does not call
> malloc() and then memset(). It directly calls:
>
> mem = HeapAlloc(_crtheap, HEAP_ZERO_MEMORY, size);
>
> which possibly only reserves allocate-and-zero-fill-on-demand pages for
> later.
>
> Cygwin's calloc() is different.
But then again, Cygwin's malloc *is* slow, particulary in
memory-demanding multi-threaded scenarios since that serializes all
malloc/free calls.
The memory handling within Cygwin is tricky. Attempts to replace good
old dlmalloc with a fresher jemalloc or ptmalloc failed, but that only
means the developer (i.e., me, in case of ptmalloc) was too lazy...
busy! I mean busy... to pull this through.
Having said that, if somebody would like to take a stab at replacing
dlmalloc with something leaner, I would be very happy and assist as
much as I can.
Corinna
--
Corinna Vinschen Please, send mails regarding Cygwin to
Cygwin Maintainer cygwin AT cygwin DOT com
Red Hat
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next prev parent reply other threads:[~2018-01-12 14:33 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-01-12 7:19 Lee
2018-01-12 8:38 ` Eliot Moss
2018-01-12 9:07 ` Marco Atzeri
2018-01-12 10:52 ` Lee
2018-01-21 11:01 ` Marco Atzeri
2018-01-12 14:05 ` Christian Franke
2018-01-12 14:33 ` Corinna Vinschen [this message]
2018-01-12 19:59 ` cyg Simple
2018-01-12 20:07 ` cyg Simple
2018-01-12 20:41 ` Corinna Vinschen
2018-01-12 22:34 ` cyg Simple
2018-01-13 10:48 ` Lee
2018-01-13 10:04 ` Lee
2018-01-12 22:00 ` Eliot Moss
2018-01-13 8:35 ` Lee
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