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Date:      Sat, 07 Mar 1998 23:48:52 -0800
From:      Mike Smith <mike@smith.net.au>
To:        Julian Elischer <julian@whistle.com>
Cc:        Marc Slemko <marcs@znep.com>, Mike Smith <mike@smith.net.au>, hackers@FreeBSD.ORG
Subject:   Re: kernel wishlist for web server performance 
Message-ID:  <199803080748.XAA09061@dingo.cdrom.com>
In-Reply-To: Your message of "Sat, 07 Mar 1998 23:16:43 PST." <Pine.BSF.3.95.980307231219.16777G-100000@current1.whistle.com> 

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> I would like to add here that in FreeBSD's unified VM/Buffer cache,
> a mmapped file IS the buffer cache
> so that a send() from an mmapped file IS copying direct fromt he buffer
> cache. Ther eis ONE copy.. that from the buffer cache, into the mbuf.
> 
> (assuming that the data got into the memory via DMA in the first place..)
> you may need to have a subprocess go through and tuch all the pages to
> get them into ram first.. 

The copyin will do this.  This is why I couldn't see a real performance 
benefit outside of the convenience factor, and the mbuf shuffling 
alluded to.

-- 
\\  Sometimes you're ahead,       \\  Mike Smith
\\  sometimes you're behind.      \\  mike@smith.net.au
\\  The race is long, and in the  \\  msmith@freebsd.org
\\  end it's only with yourself.  \\  msmith@cdrom.com



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