Date: Wed, 3 Nov 2004 09:44:03 +0800 (WST) From: David Adam <zanchey@ucc.gu.uwa.edu.au> To: Joel Dahl <joel@automatvapen.se> Cc: freebsd-doc@FreeBSD.org Subject: Re: docs/73429: [patch] Update Handbook, Chapter 8, kernel configuration Message-ID: <Pine.LNX.4.58.0411030939420.7452@mussel.ucc.gu.uwa.edu.au> In-Reply-To: <20041102183220.53DCE37E7B@smtp4-2-sn2.hy.skanova.net> References: <20041102183220.53DCE37E7B@smtp4-2-sn2.hy.skanova.net>
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On Tue, 2 Nov 2004, Joel Dahl wrote: > - <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 ADAPTIVE_GIANT > + 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.</para> This is the opinion of a relative outsider, but... After reading the above (new) paragraph, I understand more about FreeBSD's internal workings, something of the future of this statement and exactly what ADAPTIVE_GIANT is. All good. Unfortunately, I really can't tell - as a relative newbie - whether that leaving it in/out is a good idea (I assume it's probably good for performance and doesn't break too much stuff, hence its inclusion in GENERIC). How about a sentence that says "If you're not sure/If you want to do X/If your mother is not a hamster, then you should leave this in/can safely comment this out."? Cheers, David Adam (member of The Great Unwashed) zanchey@ucc.gu.uwa.edu.au
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