From: "Alejandro Riveira Fernández" <ariveira@gmail.com>
To: Joshua Hintze <joshh@imsar.com>
Cc: linux-kernel@vger.kernel.org, linux-ide@vger.kernel.org
Subject: Re: PATA IDE is slower in newer versions of kernel
Date: Fri, 17 Sep 2010 15:47:32 +0200 [thread overview]
Message-ID: <20100917154732.330c4b1b@varda> (raw)
In-Reply-To: <00d401cb55f7$33a78210$9af68630$@com>
El Thu, 16 Sep 2010 17:30:51 -0600
"Joshua Hintze" <joshh@imsar.com> escribió:
[ Just CC linux-ide ]
> Hello,
>
> I've been digging into this for a couple weeks now. I have an embedded board
> that runs Linux Kernel 2.6.10 that is connected to a SSD over a PATA
> connection. Data is transferred using UDMA4 speeds and I get a nice
> sustained write speed of about 20 MBps which is adequate for us.
>
> I have recently taken the plunge to update to a newer version of the kernel
> starting at 2.6.32 (also tried 2.6.33) and what I am seeing writes speeds
> drop to about 18 MBps peak with large jumps going from 8 MBps->16 MBs for
> sustained throughput.
>
> I decided to read up on the ATA specification and I connected a logic
> analyzer to the PATA bus and here is what is happening...after a large chunk
> of data is written to the device, instead of the device pausing the transfer
> by asserting DDMARDY it actual initiates a device data-out termination by
> pulling DMARQ low.
>
> The old kernel 2.6.10 responds to this by strobing the STOP line 8 times
> within 800uS and the device releases DMARQ shortly afterwards. On the newer
> kernels the strobing of the STOP line takes near 8mS of time. Since the hard
> drive only release DMARQ after this 8 pulse strobe I believe this is the
> cause of the slower write speeds on the newer kernels. This whole process
> happens thousands of times when writing megs of data. So those extra 7mS
> begin to add up fast.
>
> My problem is I've been digging through the ide.c/ide-dma.c and other code
> but I'm not exactly sure where the code would jump to upon a device
> initiated termination on a data-out dma transfer.
>
> My guess is ide_dma_intr(...). Is this correct?
>
> Any other areas I could look at?
>
> Thanks in advance.
>
>
> --
> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at http://vger.kernel.org/majordomo-info.html
> Please read the FAQ at http://www.tux.org/lkml/
WARNING: multiple messages have this Message-ID (diff)
From: "Alejandro Riveira Fernández" <ariveira@gmail.com>
To: "Joshua Hintze" <joshh@imsar.com>
Cc: <linux-kernel@vger.kernel.org>, linux-ide@vger.kernel.org
Subject: Re: PATA IDE is slower in newer versions of kernel
Date: Fri, 17 Sep 2010 15:47:32 +0200 [thread overview]
Message-ID: <20100917154732.330c4b1b@varda> (raw)
In-Reply-To: <00d401cb55f7$33a78210$9af68630$@com>
El Thu, 16 Sep 2010 17:30:51 -0600
"Joshua Hintze" <joshh@imsar.com> escribió:
[ Just CC linux-ide ]
> Hello,
>
> I've been digging into this for a couple weeks now. I have an embedded board
> that runs Linux Kernel 2.6.10 that is connected to a SSD over a PATA
> connection. Data is transferred using UDMA4 speeds and I get a nice
> sustained write speed of about 20 MBps which is adequate for us.
>
> I have recently taken the plunge to update to a newer version of the kernel
> starting at 2.6.32 (also tried 2.6.33) and what I am seeing writes speeds
> drop to about 18 MBps peak with large jumps going from 8 MBps->16 MBs for
> sustained throughput.
>
> I decided to read up on the ATA specification and I connected a logic
> analyzer to the PATA bus and here is what is happening...after a large chunk
> of data is written to the device, instead of the device pausing the transfer
> by asserting DDMARDY it actual initiates a device data-out termination by
> pulling DMARQ low.
>
> The old kernel 2.6.10 responds to this by strobing the STOP line 8 times
> within 800uS and the device releases DMARQ shortly afterwards. On the newer
> kernels the strobing of the STOP line takes near 8mS of time. Since the hard
> drive only release DMARQ after this 8 pulse strobe I believe this is the
> cause of the slower write speeds on the newer kernels. This whole process
> happens thousands of times when writing megs of data. So those extra 7mS
> begin to add up fast.
>
> My problem is I've been digging through the ide.c/ide-dma.c and other code
> but I'm not exactly sure where the code would jump to upon a device
> initiated termination on a data-out dma transfer.
>
> My guess is ide_dma_intr(...). Is this correct?
>
> Any other areas I could look at?
>
> Thanks in advance.
>
>
> --
> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at http://vger.kernel.org/majordomo-info.html
> Please read the FAQ at http://www.tux.org/lkml/
next prev parent reply other threads:[~2010-09-17 13:47 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-09-16 23:30 PATA IDE is slower in newer versions of kernel Joshua Hintze
2010-09-17 13:47 ` Alejandro Riveira Fernández [this message]
2010-09-17 13:47 ` Alejandro Riveira Fernández
2010-09-18 17:12 ` Joshua Hintze
2010-09-18 17:12 ` Joshua Hintze
2010-09-18 19:22 ` Maxim Levitsky
2010-09-18 19:43 ` Joshua Hintze
2010-09-18 19:43 ` Joshua Hintze
2010-09-18 19:47 ` Randy Dunlap
2010-09-18 19:47 ` Randy Dunlap
2010-09-18 20:02 ` Joshua Hintze
2010-09-18 20:02 ` Joshua Hintze
2010-09-18 20:04 ` Arnd Bergmann
2010-09-19 0:59 ` Alan Cox
2010-09-19 0:59 ` Alan Cox
2010-09-19 4:23 ` Joshua Hintze
2010-09-19 4:23 ` Joshua Hintze
[not found] ` <4C97ACBC.3050303@mnsu.edu>
2010-09-20 19:55 ` Joshua Hintze
-- strict thread matches above, loose matches on Subject: below --
2010-09-16 21:22 Joshua Hintze
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