RE: poll function in cygwin

RE: poll function in cygwin

[Nguyen Minh Sang]

Hi !

  I has written a CHAT server that uses poll function. In linux, it's
OK. The concurrent connection I achieved is lager than 1024. But on
Win2k (compile in cygwin) then concurrent connection reach only 1023 and
the process bug: Segmentaion fault. could you help me to solve this
problem ?

Thanks and Best Regards,
sangnm.

-----Original Message-----
From: egor duda [ mailto:deo@logos-m.ru ]
Sent: Tuesday, August 27, 2002 2:27 AM
To: Corinna Vinschen
Subject: Re: poll function in cygwin


Hi!

Tuesday, 27 August, 2002 Corinna Vinschen corinna-cygwin@cygwin.com
wrote:

CV> On Tue, Aug 27, 2002 at 02:33:40PM +0700, Nguyen Minh Sang wrote:
>>    On cygwin, function:
>> int poll(struct pollfd *ufds, unsigned int nfds, int timeout);
>> 
>> The maximum of nfds = ?

CV> Theoretically there is no maximum.  In practice the maximum is a
CV> function of the memory available.

I was thinking that maximum number of handles which can be waited via
WaitForMultipleObjects() is 64, thus limiting a number of handles that
can be select()ed. It's probably possible to work around such
limitation in cygwin select() but either i've missed something or no
such workaround was created in cygwin code. 

Egor.            mailto:deo@logos-m.ru ICQ 5165414 FidoNet 2:5020/496.19


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Re: poll function in cygwin

[Christopher Faylor]

On Tue, Aug 27, 2002 at 04:46:23PM +0700, Nguyen Minh Sang wrote:
>I has written a CHAT server that uses poll function.  In linux, it's
>OK.  The concurrent connection I achieved is lager than 1024.  But on
>Win2k (compile in cygwin) then concurrent connection reach only 1023
>and the process bug: Segmentaion fault.  could you help me to solve
>this problem ?

Why not solve it yourself?  Run it under the debugger.

cgf

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Re: poll function in cygwin

[Robert Collins]

On Wed, 2002-08-28 at 12:36, Christopher Faylor wrote:


> I was not asserting that WaitForMultipleObjects could wait for >64
> handles.  I was saying that cygwin's select() can do so.

Doh. Sorry. Here is me munching my words... munch munch munch.

Rob

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Re: poll function in cygwin

[Christopher Faylor]

On Wed, Aug 28, 2002 at 11:58:20AM +1000, Robert Collins wrote:
>On Wed, 2002-08-28 at 00:54, Christopher Faylor wrote:
>>> >>I was thinking that maximum number of handles which can be waited via
>> >>WaitForMultipleObjects() is 64, thus limiting a number of handles that
>> >>can be select()ed.  It's probably possible to work around such
>> >>limitation in cygwin select() but either i've missed something or no
>> >>such workaround was created in cygwin code.
>> >
>> >Ahem, no, you're right.
>> 
>> Actually, it isn't that simple.  It depends on what you are waiting
>> for.  For instance, if you are waiting for pipes, you can wait for
>> an unlimited number of them.  If you ware waiting for sockets, I think
>> that is also true.  If you are waiting for console handles, then yes,
>> 64 is the maximum.
>
>According to MSDN, Egor is right. I wouldn't be surprised if MS allowed
>more 'silently' on new OS's though..

I was not asserting that WaitForMultipleObjects could wait for >64
handles.  I was saying that cygwin's select() can do so.

If you look at the code you might be able to see why this is so.  It's
not really worth debating however.  I just chimed in as the author of
the select code to make it clear that the issue isn't as simple as
saying that "Cygwin's select can only deal with 64 fds".  In most cases
it can handle many more than that.

cgf
(who will now probably get a lot of private email from people with select
"problems")

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Re: poll function in cygwin

[Robert Collins]

On Wed, 2002-08-28 at 00:54, Christopher Faylor wrote:
>> >>I was thinking that maximum number of handles which can be waited via
> >>WaitForMultipleObjects() is 64, thus limiting a number of handles that
> >>can be select()ed.  It's probably possible to work around such
> >>limitation in cygwin select() but either i've missed something or no
> >>such workaround was created in cygwin code.
> >
> >Ahem, no, you're right.
> 
> Actually, it isn't that simple.  It depends on what you are waiting
> for.  For instance, if you are waiting for pipes, you can wait for
> an unlimited number of them.  If you ware waiting for sockets, I think
> that is also true.  If you are waiting for console handles, then yes,
> 64 is the maximum.

According to MSDN, Egor is right. I wouldn't be surprised if MS allowed
more 'silently' on new OS's though..

Rob

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Re: poll function in cygwin

[Christopher Faylor]

On Tue, Aug 27, 2002 at 11:58:45AM +0200, Corinna Vinschen wrote:
>On Tue, Aug 27, 2002 at 01:27:03PM +0400, Egor Duda wrote:
>> Tuesday, 27 August, 2002 Corinna Vinschen corinna-cygwin@cygwin.com wrote:
>>CV> On Tue, Aug 27, 2002 at 02:33:40PM +0700, Nguyen Minh Sang wrote:
>>>>On cygwin, function: int poll(struct pollfd *ufds, unsigned int nfds,
>>>>int timeout);
>>>>
>>>>The maximum of nfds = ?
>>
>>CV> Theoretically there is no maximum.  In practice the maximum is a
>>CV> function of the memory available.
>>
>>I was thinking that maximum number of handles which can be waited via
>>WaitForMultipleObjects() is 64, thus limiting a number of handles that
>>can be select()ed.  It's probably possible to work around such
>>limitation in cygwin select() but either i've missed something or no
>>such workaround was created in cygwin code.
>
>Ahem, no, you're right.

Actually, it isn't that simple.  It depends on what you are waiting
for.  For instance, if you are waiting for pipes, you can wait for
an unlimited number of them.  If you ware waiting for sockets, I think
that is also true.  If you are waiting for console handles, then yes,
64 is the maximum.

cgf

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Re: poll function in cygwin

[Corinna Vinschen]

On Tue, Aug 27, 2002 at 01:27:03PM +0400, Egor Duda wrote:
> Hi!
> 
> Tuesday, 27 August, 2002 Corinna Vinschen corinna-cygwin@cygwin.com wrote:
> 
> CV> On Tue, Aug 27, 2002 at 02:33:40PM +0700, Nguyen Minh Sang wrote:
> >>    On cygwin, function:
> >> int poll(struct pollfd *ufds, unsigned int nfds, int timeout);
> >> 
> >> The maximum of nfds = ?
> 
> CV> Theoretically there is no maximum.  In practice the maximum is a
> CV> function of the memory available.
> 
> I was thinking that maximum number of handles which can be waited via
> WaitForMultipleObjects() is 64, thus limiting a number of handles that
> can be select()ed. It's probably possible to work around such
> limitation in cygwin select() but either i've missed something or no
> such workaround was created in cygwin code. 

Ahem, no, you're right.

Corinna

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Re: poll function in cygwin

[egor duda]

Hi!

Tuesday, 27 August, 2002 Corinna Vinschen corinna-cygwin@cygwin.com wrote:

CV> On Tue, Aug 27, 2002 at 02:33:40PM +0700, Nguyen Minh Sang wrote:
>>    On cygwin, function:
>> int poll(struct pollfd *ufds, unsigned int nfds, int timeout);
>> 
>> The maximum of nfds = ?

CV> Theoretically there is no maximum.  In practice the maximum is a
CV> function of the memory available.

I was thinking that maximum number of handles which can be waited via
WaitForMultipleObjects() is 64, thus limiting a number of handles that
can be select()ed. It's probably possible to work around such
limitation in cygwin select() but either i've missed something or no
such workaround was created in cygwin code. 

Egor.            mailto:deo@logos-m.ru ICQ 5165414 FidoNet 2:5020/496.19


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Re: poll function in cygwin

[Corinna Vinschen]

On Tue, Aug 27, 2002 at 02:33:40PM +0700, Nguyen Minh Sang wrote:
> Hi All,
> 
>    On cygwin, function: 
> int poll(struct pollfd *ufds, unsigned int nfds, int timeout);
> 
> The maximum of nfds = ?

Theoretically there is no maximum.  In practice the maximum is a
function of the memory available.

Corinna

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poll function in cygwin

[Nguyen Minh Sang]

Hi All,

   On cygwin, function: 
int poll(struct pollfd *ufds, unsigned int nfds, int timeout);

The maximum of nfds = ?

thanks,
sangnm.

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