Date: Wed, 3 Nov 2004 09:50:31 GMT From: Joel Dahl <joel@automatvapen.se> To: freebsd-doc@FreeBSD.org Subject: Re: docs/73429: [patch] Update Handbook, Chapter 8, kernel configuration Message-ID: <200411030950.iA39oV1f072344@freefall.freebsd.org>
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The following reply was made to PR docs/73429; it has been noted by GNATS.
From: Joel Dahl <joel@automatvapen.se>
To: John Baldwin <jhb@FreeBSD.org>
Cc: FreeBSD-gnats-submit@FreeBSD.org
Subject: Re: docs/73429: [patch] Update Handbook, Chapter 8, kernel
configuration
Date: Wed, 03 Nov 2004 10:46:49 +0100
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On Tue, 2004-11-02 at 22:02, John Baldwin wrote:
> Only note I have (patch looks great!) is that instead of removing SMP, you
> probably want to say that 'options SMP' should be added to include support
> for multiple processors. Note that SMP is present in GENERIC on other
> architectures such as Alpha and sparc64. There is also an 'SMP' kernel
> config for i386 and amd64.
I've attached an updated patch that includes your suggestion, and I've
improved the description of ADAPTIVE_GIANT. Thanks.
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--- chapter.sgml Sun Oct 31 09:06:48 2004
+++ new.chapter.sgml Wed Nov 3 10:26:04 2004
@@ -893,19 +893,28 @@
<programlisting>options ADAPTIVE_GIANT # Giant mutex is adaptive.</programlisting>
- <para>This option causes Giant to be included in the set of mutexes
- adaptively spun on.</para>
+ <para>Giant is the name of a mutual exclusion mechanism (a sleep mutex)
+ that protects a large set of kernel resources. Today, this is an
+ unacceptable performance bottleneck which is actively beeing replaced
+ with locks that protect individual resources. The
+ <literal>ADAPTIVE_GIANT</literal> option causes Giant to be included
+ in the set of mutexes adaptively spun on. That is, when a thread
+ wants to lock the Giant mutex, but it is already locked by a thread
+ on another CPU, the first thread will keep running and wait for the
+ lock to be released. Normally, the thread would instead go back to
+ sleep and wait for its next chance to run. If you are not sure,
+ leave this in.</para>
<indexterm>
<primary>kernel options</primary>
<secondary>SMP</secondary>
</indexterm>
- <programlisting># To make an SMP kernel, the next two are needed
-options SMP # Symmetric MultiProcessor Kernel
-device apic # I/O APIC</programlisting>
+ <programlisting>device apic # I/O APIC</programlisting>
- <para>The above are both required for SMP support, and can also be
- safely enabled on uniprocessor systems.</para>
+ <para>The apic device enables the use of I/O APIC for interrupt
+ delivery. The apic device can be used in both UP and SMP kernels, but
+ is required for SMP kernels. Add <literal>options SMP</literal> to
+ include support for multiple processors.</para>
<programlisting>device isa</programlisting>
@@ -1026,6 +1035,7 @@
device asr # DPT SmartRAID V, VI and Adaptec SCSI RAID
device ciss # Compaq Smart RAID 5*
device dpt # DPT Smartcache III, IV - See NOTES for options
+device hptmv # Highpoint RocketRAID 182x
device iir # Intel Integrated RAID
device ips # IBM (Adaptec) ServeRAID
device mly # Mylex AcceleRAID/eXtremeRAID
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