Date: Thu, 29 May 1997 17:06:22 +0200 From: Poul-Henning Kamp <phk@dk.tfs.com> To: Bruce Evans <bde@zeta.org.au> Cc: current@freebsd.org Subject: Re: disk cache challenged by small block sizes Message-ID: <373.864918382@critter.dk.tfs.com> In-Reply-To: Your message of "Thu, 29 May 1997 22:28:05 %2B1000." <199705291228.WAA11504@godzilla.zeta.org.au>
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>ufs with a block size of 4K was about the same speed as ext2fs with a block
>size of 4K. ufs with a block size of 8K was significantly (25%) slower.
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Uhm, isn't that rather obvious ?
The chances of being able to do one DMA into two (physically) consecutive
pages are very very slim as far as I can tell, so you will generally get
better performance when you do it in page size chunks ?
In other words, drivers should be optimized for two back-to-back 4K
transactions to different pages, not for 8k transactions to physically
contiguous pages.
--
Poul-Henning Kamp | phk@FreeBSD.ORG FreeBSD Core-team.
http://www.freebsd.org/~phk | phk@login.dknet.dk Private mailbox.
whois: [PHK] | phk@tfs.com TRW Financial Systems, Inc.
Power and ignorance is a disgusting cocktail.
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