[Cbe-oss-dev] [RFC,PATCH] libspe2: stop using spe_fds_refcount

[Dirk Herrendoerfer]

Kazunori Asayama <asayama at sm.sony.co.jp> wrote on 06.12.2006 11:45:31:

> I'd like to raise again an issue about use of reference counters
> for file descriptors (spe_fd_refcount) in libspe2/spebase.

I'm  aware of the issue that the code is almost useless right now, but
sine every linux process is limited to 1024 open files I see a need for
the ability to close event source files.
Right now there is no need for it, but when the preemptive scheduling
becomes available and processes start making use of more spes, and use
the files without closing them we will run out of file descriptors at about
64 spe threads.
I would propose to leave the code as ist is and close files that are not
used as frequently - the signal1&2 file for example.

> I propose to stop using spe_fds_refcount because of the following
> reasons:
>
>   1. That mechanism does not work well currently.
>
>      None decrements the counters incremented by mbox functions. That
>      means that the current implementation of the mechanism is almost
>      meaningless.

Yes, I see no reason to close files that should be accessible always and
quickly, but I'd like to close those that are only needed seldomly.
In any case all files are closed when the spe context is disposed of.

>   2. Even if the problem 1. is solved, performance issues will appear.
>
>      That is, mbox and/or SNR functions will become to close and to
>      re-open the FDs frequently. It seems quite inefficient.

See above, but the small performance loss for couting the number of users
is still better than stalling or crashing if the app runs out of
filedescriptors.

> What do you think ?
>

Hope this sheds some light on the intent of the function.

Best regards,

Dirk Herrrendoerfer

[SNIP]