Re: Syslets, Threadlets, generic AIO support, v6

On Wed, May 30, 2007 at 10:42:52AM +0200, Ingo Molnar (mingo@xxxxxxx) wrote:
it is a serious flexibility issue that should not be ignored. The
unified fd space is a blessing on one hand because it's simple and
powerful, but it's also a curse because nested use of the fd space for
libraries is currently not possible. But it should be detached from any
fundamental question of kevent vs. epoll. (By improving library use of
file descriptors we'll improve the utility of all syscalls - by ducking
to a memory based API we only solve that particular event based usage.)

There is another issue with file descriptors - userspace must dig into
kernel each time it wants to get a new set of events, while with memory
based approach it has them without doing so. After it has returned from
kernel and know that there are some evetns, kernel can add more of them
into the ring (if there is a place) and userspace will process them
withouth additional syscalls.
Although syscall overhead is very small, it does exist and should not be
ignored in the design.


Ingo

--
Evgeniy Polyakov
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