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From: Willy Tarreau <>
Subject: [PATCH 0/2] libata: implement 32-bit transfers for PIO mode
Date: Sun, 17 Feb 2008 22:18:10 +0100	[thread overview]
Message-ID: <> (raw)

Hi Jeff,

For several times I tried libata on small machines equipped with either
CompactFlash or IDE DOM (Disk-On-Module). All those machines with small
flashes (<= 256 MB) were about 35-40% slower under libata than under the
plain old IDE driver. I realized that all the slower ones were running
PIO only.

Today I had time to investigate the issue on a Geode LX board. At first
I thought it was the pata_cs5536 driver which would have incorrect timings,
but this was not the case. I finally noticed that under IDE, my flashes
were running in 32-bit mode while I could not enable 32-bit with libata.

Reading ata_data_xfer() made it obvious that transfers were only 16-bit

Thus, I have implemented the 32-bit mode to bring the performance back
to the level of the old IDE driver. I jumped from 1.5 MB/s to 2.5 MB/s,
which is an important difference at this level of performance, especially
when large files are read. The 32-bit mode is enabled using the ioctl
which is already implemented but only accepts a null value.

I'm joining two patches which I hope you'll consider for inclusion. I've
updated them to latest Linus' git.

Best regards,

             reply	other threads:[~2008-02-17 21:18 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2008-02-17 21:18 Willy Tarreau [this message]
2008-02-17 21:19 ` [PATCH 1/2] libata: implement ATA_IOC_GET_IO32/ATA_IOC_SET_IO32 ioctls Willy Tarreau
2008-04-17 19:49   ` Jeff Garzik
2008-04-17 19:46     ` Willy Tarreau
2008-04-17 22:02     ` [PATCH] libata: implement support for 32-bit PIO transfers Willy Tarreau
2008-02-17 21:20 ` [PATCH 2/2] " Willy Tarreau
2008-02-17 22:32   ` Alan Cox
2008-02-17 22:31 ` [PATCH 0/2] libata: implement 32-bit transfers for PIO mode Alan Cox
2008-02-17 23:08   ` Willy Tarreau

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