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megaraid-sas driver performance worse than on-board sata_nv

Bug 12752 [email protected] 1 participant 5 messages Jun 10, 2011 – May 30, 2012 1 message not in the archive SCSI

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https://bugzilla.kernel.org/show_bug.cgi?id=12752

devsk <[email protected]> changed:

What |Removed |Added
----------------------------------------------------------------------------
Regression|--- |No

--- Comment #1 from devsk <[email protected]> 2011-06-10 04:03:18 --- Wow! 2+ years and this bug has not even be looked at by a dev. How is this driver in the kernel if its not maintained?

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https://bugzilla.kernel.org/show_bug.cgi?id=12752

Adam Radford <[email protected]> changed:

What |Removed |Added
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CC| |[email protected]

--- Comment #2 from Adam Radford <[email protected]> 2011-06-10 23:05:02 --- devsk,

I'm sorry about you not getting a response from the previous megaraid_sas developer. He was probably not watching bugzilla.kernel.org.

There is nothing in the driver that will 'throttle' the I/O on your PERC5 controller.

The software raid code sets various read-ahead values in the block layer request_queues it sets up:

# grep -i "ra_pages" *
raid0.c:         * If an individual device has an ra_pages greater than the
raid0.c:                if (mddev->queue->backing_dev_info.ra_pages < 2*
stripe)
raid0.c:                        mddev->queue->backing_dev_info.ra_pages = 2*
stripe;
raid10.c:               if (mddev->queue->backing_dev_info.ra_pages < 2*
stripe)
raid10.c:                       mddev->queue->backing_dev_info.ra_pages = 2*
stripe;
raid5.c:                if (mddev->queue->backing_dev_info.ra_pages < 2 *
stripe)
raid5.c:                        mddev->queue->backing_dev_info.ra_pages = 2 *
stripe;
raid5.c:                        if
(conf->mddev->queue->backing_dev_info.ra_pages < 2 * stripe)
raid5.c:                               
conf->mddev->queue->backing_dev_info.ra_pages = 2 * stripe;

Can you try setting some OS read-ahead values (on top of the controller doing read-ahead) for the scsi device attached to your PERC5 controller and re-running
your tests?

i.e.:

/sbin/blockdev --getra /dev/sda (See what you have set currently) /sbin/blockdev --setra 8192 /dev/sda (Set read ahead for sda to 8192 sectors) /sbin/blockdev --setra 16834 /dev/sda (Set read ahead for sda to 16384 sectors)

This may cause more I/O to be issued to the card from the OS and may improve your bonnie++ results.

-Adam

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https://bugzilla.kernel.org/show_bug.cgi?id=12752

--- Comment #3 from devsk <[email protected]> 2011-06-12 18:51:18 --- Adam,

Thanks for the response! Yeah, I had played with readahead at that time and it did make some difference but not much. I sold my Perc card some time ago. I don't have this issue now. Please close the bug.

Sorry if this was unnecessary digression for you. That was not my intention.

-devsk

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Alan <[email protected]> changed:

What |Removed |Added
----------------------------------------------------------------------------

             Status|NEW                         |RESOLVED
                 CC|                            |[email protected]
         Resolution|                            |UNREPRODUCIBLE
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