From: cyg Simple <cygsimple@gmail.com>
To: cygwin@cygwin.com
Subject: Re: calloc speed difference
Date: Fri, 12 Jan 2018 22:34:00 -0000 [thread overview]
Message-ID: <3acfae95-e62b-40d5-d094-44e651dd6b79@gmail.com> (raw)
In-Reply-To: <20180112204149.GF24623@calimero.vinschen.de>
On 1/12/2018 3:41 PM, Corinna Vinschen wrote:
> On Jan 12 14:59, cyg Simple wrote:
>> On 1/12/2018 9:33 AM, Corinna Vinschen wrote:
>>> On Jan 12 15:06, Christian Franke wrote:
>>>> 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.
>>
>> Corina, how reliable is the Cygwin time function on a non-Cygwin
>> executable? Isn't this a comparison of apples to oranges?
>
> I wasn't comparing, in fact. I was just saying that Cygwin's malloc
> is slow, partially because dlmalloc is not the fastest one, partially
> due to the serialization overhead in multithreading scenarios.
No, but the OP *is* doing a compare. From what I remember doing a time
comparison of a non-Cygwin app compared to a Cygwin app isn't really a
logical comparison. Even if the two were a Cygwin app multiple runs of
the same app will show variance.
--
cyg Simple
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next prev parent reply other threads:[~2018-01-12 22:34 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
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 [this message]
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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