Mail Archives: cygwin/2006/08/02/21:11:24
Vladimir Dergachev wrote:
> Hi Gary and Larry,
>
> Thank you for your comments, replies below:
>
> On Wednesday 02 August 2006 7:08 pm, you wrote:
>>> Any suggestions and comments would be greatly
>>> appreciated.
>>> Please CC me - I am not on the list.
>>>
>>> thank you very much
>>>
>>> Vladimir Dergachev
>> I'll try your test case when I get a chance, but my WAG is that you're
>> seeing the effects of Cygwin's creation of sparse files by default for any
>> file beyond a certain size. I unfortunately do not recall what that size
>> is. What happens as you change FILE_SIZE and/or BUFFER_SIZE in your
>> script, to maybe a small multiple of your cluster size?
>
> I tried buffer_size of 10K, 100K, 1M and 10M - no big difference, except a
> small decrease in number of fragments for 10M value - could be noise..
>
> I also tried a smaller file size - 3M, the number of fragments decreased to
> 33, roughly proportionally to size.
>
> Unfortunately, I do not know what cluster size is.
>
> With regard to sparse files the intent here is to open a file, write data to
> it and the close. No seeks involved, much less void regions. I do understand
> that internally cygwin could do something different.
>
> I have not found a utility to identify a sparse file yet - if you happen to
> have a link I would greatly appreciate it.
>
> Also, I tried the following experiment - found a 17 MB file in ibiblio.org and
> downloaded it with FireFox. The file ended up fragmented into more than 200
> pieces. Tried the same file with IE - no fragmentation.
>
> It could be, of course, that Firefox is compiled with cygwin, but I have not
> found cygwin.dll anywhere in its installation directory.
If you pulled it from Mozilla.org, it ain't Cygwin-based. That would point to
a more general, non-Cygwin problem.
> PS I'll try writing a C program when time permits - any suggestions on what
> API besides regular open/write/close to use ?
I would recommend making a POSIX API version and a straight Win32 version.
But if what you said about Firefox is true, you should see a similar problem
even using MinGW (www.mingw.org) or the '-mno-cygwin'. Again, that would
point to this being a non-Cygwin problem, though still quite an annoying one.
--
Larry Hall http://www.rfk.com
RFK Partners, Inc. (508) 893-9779 - RFK Office
216 Dalton Rd. (508) 893-9889 - FAX
Holliston, MA 01746
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