From: "Russ Cox" <rsc@plan9.bell-labs.com>
To: 9fans@cse.psu.edu
Subject: Re: [9fans] select()
Date: Thu, 16 Nov 2000 17:43:15 -0500 [thread overview]
Message-ID: <20001116224334.5EC75199E6@mail.cse.psu.edu> (raw)
In http://plan9.bell-labs.com/sys/doc/9.html, there's a hint that Plan 9's
design avoids some of the nastiness with select() here:
Compare this to the UNIX select system call: select applies only
to a restricted set of devices, legislates a style of
multiprogramming in the kernel, does not extend across networks,
is difficult to implement, and is hard to use.
Would someone be so kind as to elaborate? It looks like select() is
implemented very much like BSD select() in the APE.
Select in the APE is implemented entirely at user level,
with no help from the kernel. It continually calls sleep(100)
and then checks for input. Select on most Unix systems
is a system call, which requires the kernel to do all that
and usually more. Further, since select requires that at most
one of the reads succeeds, it is very hard to implement once
you have file systems coming from somewhere other than
local resources (e.g., any network file system). It also often
makes for awkward program structure.
The passage you quote is, I believe, arguing that Alef's
style of multiprogramming is a better solution than select,
not that Plan 9 makes select easier to implement. Select is
inherently hard to implement because of its specification.
Rob argues the benefits of a precursor to the Plan 9 style
of multiprogramming more extensively in
http://plan9.bell-labs.com/cm/cs/doc/89/1-a.ps.gz.
Russ
next reply other threads:[~2000-11-16 22:43 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2000-11-16 22:43 Russ Cox [this message]
-- strict thread matches above, loose matches on Subject: below --
2000-11-16 2:10 Stephen M Wynne
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20001116224334.5EC75199E6@mail.cse.psu.edu \
--to=rsc@plan9.bell-labs.com \
--cc=9fans@cse.psu.edu \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).