From: Andrew Morton <akpm@zip.com.au>
To: lkml <linux-kernel@vger.kernel.org>
Subject: Re: [patch 12/13] direct IO updates
Date: Sun, 28 Jul 2002 02:11:40 -0700 [thread overview]
Message-ID: <3D43B54C.E33BF47F@zip.com.au> (raw)
In-Reply-To: 3D439E47.A227A2B7@zip.com.au
Andrew Morton wrote:
>
> ...
>
> And against four IDE disks on an HPT374 controller. Throughput is 120
> megabytes/sec:
>
> c01eed8c 80 0.292462 end_that_request_first
> c01fe850 87 0.318052 hpt3xx_intrproc
> c01ed574 123 0.44966 blk_rq_map_sg
> c01f8f10 141 0.515464 ata_select
> c014db38 153 0.559333 do_direct_IO
> c010bb78 235 0.859107 timer_interrupt
> c01f9144 281 1.02727 ata_irq_enable
> c01ff990 290 1.06017 udma_pci_init
> c01fe878 308 1.12598 hpt3xx_maskproc
> c02006f8 379 1.38554 idedisk_do_request
> c02356a0 609 2.22637 pci_conf1_read
> c01ff8dc 611 2.23368 udma_pci_start
> c01ff950 922 3.37062 udma_pci_irq_status
> c01f8fac 1002 3.66308 ata_status
> c01ff26c 1059 3.87146 ata_start_dma
> c01feb70 1141 4.17124 hpt374_udma_stop
> c01f9228 3072 11.2305 ata_out_regfile
> c01052d8 15193 55.5422 poll_idle
>
> Not so good.
Actually...
The adaptecs are on different PCI buses, so there is plenty of
spare PCI capacity.
The HPT374 is on a single 33MHz/32bit PCI bus, which is saturated.
So CPU access to the IDE controller registers will be contending
with all that busmastering traffic, which may explain a lot of
this difference.
-
prev parent reply other threads:[~2002-07-28 8:59 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2002-07-28 7:33 [patch 12/13] direct IO updates Andrew Morton
2002-07-28 9:11 ` Andrew Morton [this message]
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