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Date:      Wed, 27 Feb 2002 12:19:03 -0800
From:      Alfred Perlstein <bright@mu.org>
To:        Matthew Dillon <dillon@apollo.backplane.com>
Cc:        Julian Elischer <julian@elischer.org>, Jeff Roberson <jroberson@chesapeake.net>, arch@FreeBSD.ORG
Subject:   Re: Slab allocator
Message-ID:  <20020227201903.GS80761@elvis.mu.org>
In-Reply-To: <200202271955.g1RJtAj30178@apollo.backplane.com>
References:  <200202271926.g1RJQCm29905@apollo.backplane.com> <Pine.BSF.4.21.0202271128580.97278-100000@InterJet.elischer.org> <20020227194256.GR80761@elvis.mu.org> <200202271955.g1RJtAj30178@apollo.backplane.com>

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* Matthew Dillon <dillon@apollo.backplane.com> [020227 11:55] wrote:
> 
> :
> :* Julian Elischer <julian@elischer.org> [020227 11:40] wrote:
> :> 
> :> 
> :> On Wed, 27 Feb 2002, Matthew Dillon wrote:
> :> 
> :> > 
> :> > :PS Sorry for the long winded email. :-)
> :> > 
> :> >     Well, one thing I've noticed right off the bat is that the code
> :> >     is trying to take advantage of per-cpu queues but is still
> :> >     having to obtain a per-cpu mutex to lock the per-cpu queue.
> :> 
> :> I was wondering abuot that myself :-)
> :
> :It's basically the pre-emption stuff you guys are wondering about
> :along with the possiblity of free'ing back to another cpu's
> :cache that may be an issue.
> :
> :Jeff, are you fee'ing memory back to the cache it was initially
> :allocated from or not?
> :
> :-Alfred
> 
>     I don't know what Jeff is doing there but I do seem to recall a
>     paper from somewhere that indicated it was more efficient to free memory
>     to the current cpu's per-cpu cache rather then back to the original
>     cpu's cache because the current cpu's hardware L1/L2 cache likely already
>     has mastership of the memory.  I think Linux does things this way.

Last I checked linux does not.

the stuff we both are talking about (free'ing back to original
cache) is detailed in the 'Horde' memory allocator which is hard
to find online.

-- 
-Alfred Perlstein [alfred@freebsd.org]
'Instead of asking why a piece of software is using "1970s technology,"
 start asking why software is ignoring 30 years of accumulated wisdom.'
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