Date: Wed, 17 Jan 2001 14:23:43 -0500 From: Trent Nelson <tpnelson@switch.com> To: freebsd-hackers@FreeBSD.org Subject: Network I/O multiplexing questions. Message-ID: <20010117142343.A1144@dhcp103-172-16-3.switch.com>
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Hi,
1. Is there any performance/efficiency gained when read and write
operations on multiple sockets are grouped together? That is, after
the I/O multiplexer function returns (i.e. select/poll/kevent), all
read operations on sockets are done together (say, encapsulated by
a thread, perhaps) and likewise for write operations.
I'm looking into writing something that uses the reply from kevent()
to construct independent lists of read/write/error operations
pending on multiple sockets. Some sort of executable entity
(event-thread, state-thread, pthread, etc) will be responsible for
processing the pending events and I figured the best performance
would be gained if each execution stream is solely responsible for
*only* doing read/write operations. Pthreads probably aren't a good
example of a scheduleable entity given their scheduling criteria
isn't predictable.
2. Does "The Design and Implementation of the 4.4BSD Operating System"
deal with how send/recv operations take place from receiving the
data from the network interface, traversing the protocol hierarchy
and eventually passing into user space? Is the text's coverage of
this outdated in any way?
3. What conditions, if any, are used to deem whether a read or write
to a socket will block? Is there any quick and efficient way of
doing this in userspace? I'm assuming it has something to do with
the hi/lo watermarks of a socket and its associated I/O buffer.
Can anyone point me to instances of kernel source code where a check
is made to see if a socket will block?
4. Currently, if a process blocks on network I/O, is it immediately
switched out of execution by the scheduler?
5. Has anyone taken a look at the State-Threads API proposed by SGI?
Has anyone considered adding support for our kevent/kqueue multi-
plexing method in addition to the select/poll methods offered?
(http://oss.sgi.com/projects/state-threads/)
Thanks in advance.
Regards,
Trent.
--
Trent Nelson - Software Engineer - tpnelson@switch.com
"A man with unlimited enthusiasm can achieve
almost anything." --unknown
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