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Date: Wed, 17 Jan 2001 16:58:14 -0800 (PST)
From: Jin Guojun <jin@shasta.panasas.com>
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To: FreeBSD-gnats-submit@freebsd.org
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Subject: kern/24418: read/write in thread library (-lc_r) does not do context switch
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>Number:         24418
>Category:       kern
>Synopsis:       read/write in thread library (-lc_r) does not do context switch
>Confidential:   no
>Severity:       critical
>Priority:       high
>Responsible:    freebsd-bugs
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Wed Jan 17 17:00:00 PST 2001
>Closed-Date:
>Last-Modified:
>Originator:     Jin Guojun
>Release:        FreeBSD 4.2-RELEASE i386
>Organization:
>Environment:

	FreeBSD STABLE and CURRENT

>Description:

	threaded read/write shoule not block on I/O till I/O completion.
	Blocking on I/O causes thread I/O meaningless.

	read does context switch on stdin, and this is probably only
	I/O sys-call that FreeBSD does the context switch on thread.
	Thread does not do context switch on disk I/O and timed select().
	I have not tested accept() and network I/O yet.

	Linux 2.2.x does not do context switch on thread I/O either,
	but linux 2.4.0 fixed it.
	Solaris does this well.
	Both Solaris and Linux 2.4.0 submit the I/O job to the driver,
	and immediately switch context to another thread regardless
	how less the I/O data is.
	This contest switch utilizes both system CPU and I/O CPU time.

>How-To-Repeat:

	

>Fix:



>Release-Note:
>Audit-Trail:
>Unformatted:


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