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Date: Wed, 02 Apr 2003 15:31:14 -0800
From: Terry Lambert <tlambert2@mindspring.com>
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To: Peter Wemm <peter@wemm.org>
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Subject: Re: libthr and 1:1 threading.
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Peter Wemm wrote:
> No.  It gives the ability for a thread to block on a syscall without
> stalling the entire system.  Just try using mysqld on a system using libc_r
> and heavy disk IO.  You can't select() on a read() from disk.  Thats the
> ultimate reason to do it.  The SMP parallelism is a bonus.

Bug in FreeBSD's NBIO implementation.  A read() that would result
in page-in needs to queue the request, but return EAGAIN to user
space to indicate the request cannot be satisfied.  Making select()
come true for disk I/O after the fault is satisfied is a seperate
issue.  Probably need to pass the fd all the way down.

-- Terry