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Re: Allow customizing of __FD_SETSIZE


On Thu, Jun 10, 2010 at 6:26 AM, Christoph Kling
<christoph@familiekling.de> wrote:
> I need a raise the FD_SETSIZE for an application's select() (see misc/sys/select.h) above the default of 1024, which is defined in bits/typesizes.h as a macro __FD_SETSIZE.
>
> The only way I found is to change the system's header file bits/typesizes.h. I therefore suggest to add a #ifndef __FD_SETSIZE to bits/typesizes.h in order to allow a developer to customize FD_SETSIZE. When I sent this proposal to the libc-alpha mailing list, I was rejected by the moderator and advised to open a bugzilla enhancement request and to discuss this request on the libc-help mailing list.
>
> The link to the bugzilla entry is http://sources.redhat.com/bugzilla/show_bug.cgi?id=11687
>
> What do you think about my proposition? How can we improve the bugzilla entry so that it is being accepted by libc-alpha? Unfortunately, I am not an expert for glibc.

The kernel __kernel_fd_set only supports 1024 file descriptors.

(a) Have you patched your kernel to support more?

(b) What are you doing for old programs that would only support 1024,
how does the kernel detect those programs and avoid using the
unavailable additional file descriptor bits?

Unfortunately your problem is much more complicated than simply
increasing the value in a header. This is an ABI issue.

Does that answer your question?

Cheers,
Carlos.


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