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Date:      Sun, 25 Nov 2007 16:48:30 -0800
From:      Doug Barton <dougb@FreeBSD.org>
To:        Roman Divacky <rdivacky@freebsd.org>
Cc:        binto <binto@triplegate.net.id>, freebsd-hackers@freebsd.org, Robert Watson <rwatson@freebsd.org>
Subject:   Re: Before & After Under The Giant Lock
Message-ID:  <474A17DE.7010804@FreeBSD.org>
In-Reply-To: <20071125211807.GA12250@freebsd.org>
References:  <474830F9.90305@zirakzigil.org>	<6eb82e0711240638g2cc1e54o1fb1321cafe8ff9f@mail.gmail.com>	<1188.202.127.99.4.1195957922.squirrel@webmail.triplegate.net.id>	<20071125110116.U63238@fledge.watson.org>	<20071125143546.V6583@cauchy.math.missouri.edu> <20071125211807.GA12250@freebsd.org>

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Roman Divacky wrote:
> On Sun, Nov 25, 2007 at 02:41:35PM -0600, Stephen Montgomery-Smith wrote:
>>
>> On Sun, 25 Nov 2007, Robert Watson wrote:
>>
>>> ........................
>>> In FreeBSD 8, I expect we'll see a continued focus on both locking 
>>> granularity and improving opportunities for kernel parallelism by better 
>>> distributing workloads over CPU pools.  This is important because the 
>>> number of cores/chip is continuing to increase dramatically, so MP 
>>> performance is going to be important to keep working on.  That said, the 
>>> results to date have been extremely promising, and I anticipate that we 
>>> will continue to find ways to better exploit multiprocessor hardware, 
>>> especially in the network stack.
>>>
>> I just want to add my 2 cents, that my recent experience with FreeBSD MP 
>> has been extremely positive.  I tend to use highly CPU bound MP programs, 
>> typically lots and lots of floating point operations.  It used to be that 
>> Linux beat FreeBSD hands down - now FreeBSD seems to have a slight edge! 
>> Basically my program runs about twice as fast when I run two threads as 
>> opposed to one - I cannot see doing any better than that!
> 
> pure computation does not need kernel operations most of the time.. ie. 
> multi-threading kernel wont help much ;)

It has an indirect benefit by (presumably) not being in contention
with the userland process, and not needing slap Giant on the whole
system every few milliseconds.

Doug

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