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Re: Limits of the 965 chipset & 3 PCI-e cards/southbridge? ~774MiB/s peak for read, ~650MiB/s peak for write?

Previous thread: pppd and 2.6.25 serial driver by Chris Vine on Sunday, June 1, 2008 - 4:56 pm. (5 messages)

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[view original message]
From: Daniel J Blueman <daniel.blueman@...>
To: Justin Piszcz <jpiszcz@...>
Cc: Linux Kernel <linux-kernel@...>
Subject: Re: Limits of the 965 chipset &amp; 3 PCI-e cards/southbridge? ~774MiB/s peak for read, ~650MiB/s peak for write?
Date: Sunday, June 1, 2008 - 5:23 pm

Nice test. The Seagate 7200.11 drives deliver 120MB/s (outer zone,

raw) each, and there is an issue with CFQ dispatching requests; see:


http://groups.google.co.uk/group/linux.kernel/browse_thread/thread/b8826...


A quick workaround tweak is:


# echo 0 >/sys/block/sda/queue/iosched/slice_idle


Does this help any? This gives the difference of ~68MB/s vs ~120MB/s

on my 7200.11 ;-) .


That said, the i965 chipset is fairly contemporary, but if that 2GB/s

DMI connection is the bidirectional bandwidth (likely), then maybe

you're hitting that limit: Intel's DMI bus is based on PCIe, thus will

use 128 byte PCI-e Max Payload packets (as in the rest of the

chipset), which IIRC theoretically maxes you out near 800MB/s.


The X48 chipset may allow you to crank the Max Payload to 256 (setpci

and the Intel chipset docs), if it doesn't default to 256, like in

5400 server chipsets. This chipset is where the fun really starts eg

hdparm -T giving >10GB/s, like in Itanium2s ;-) .


Thanks,

  Daniel

--

Daniel J Blueman

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[view original message]
From: Justin Piszcz <jpiszcz@...>
To: Daniel J Blueman <daniel.blueman@...>
Cc: Linux Kernel <linux-kernel@...>
Subject: Re: Limits of the 965 chipset &amp; 3 PCI-e cards/southbridge? ~774MiB/s peak for read, ~650MiB/s peak for write?
Date: Sunday, June 1, 2008 - 7:43 pm

slice 0 does help a little with my 10-disk raid5 for sequential

read/writes:


http://home.comcast.net/~jpiszcz/raid/20080601/raid5.html

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[view original message]
From: Justin Piszcz <jpiszcz@...>
To: Daniel J Blueman <daniel.blueman@...>
Cc: Linux Kernel <linux-kernel@...>
Subject: Re: Limits of the 965 chipset &amp; 3 PCI-e cards/southbridge? ~774MiB/s peak for read, ~650MiB/s peak for write?
Date: Sunday, June 1, 2008 - 5:26 pm

Unfortunately the disks have been removed from the host, only to test

Very interesting, do you know what AMD uses for their boards by any chance?

I'll most likely stick with some type of Intel chipset but was curious

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Previous thread: pppd and 2.6.25 serial driver by Chris Vine on Sunday, June 1, 2008 - 4:56 pm. (5 messages)

Next thread: Re: [drm:radeon_cp_idle] *ERROR* radeon_cp_idle called without lock held by Dave Airlie on Sunday, June 1, 2008 - 6:11 pm. (2 messages)