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Date:      Fri, 6 Jan 2006 10:55:02 +0000
From:      Scott Mitchell <scott+lists.freebsd@fishballoon.org>
To:        Michael Vince <mv@roq.com>
Cc:        freebsd-stable@freebsd.org
Subject:   Re: 6.0 on Dell 1850 with PERC4e/DC RAID?
Message-ID:  <20060106105501.GA19690@llama.fishballoon.org>
In-Reply-To: <43BDD444.80509@roq.com>
References:  <20060105224150.GA991@tuatara.fishballoon.org> <43BDD444.80509@roq.com>

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On Fri, Jan 06, 2006 at 01:21:56PM +1100, Michael Vince wrote:
> FYI there also has been a big update to the amr driver which claims to 
> dramatically increase performance among other things, interestingly 
> enought it was augmented by Yahoo, I can only assume they are moving to 
> Dell, yahoo for me (and now you :).
> The updates are still in -current but it will be MFC'ed into stable 
> sooner or later.
> 
> http://lists.freebsd.org/pipermail/cvs-src/2005-December/056814.html

Yeah, I saw that, and it sounds most excellent.  Good to see some real
support from the likes of Dell and LSI, too. 

I might be able to get away with running -stable on this machine, but
-current will be right out.  Hopefully these changes can be MFCed in time
for 6.1.

	Scott

>  Log:
>  Mega update to the LSI MegaRAID driver:
>  
>  1.  Implement a large set of ioctl shims so that the Linux management apps
>  from LSI will work.  This includes infrastructure to support adding, 
>  deleting
>  and rescanning arrays at runtime.  This is based on work from Doug 
>  Ambrosko,
>  heavily augmented by LSI and Yahoo.
>  
>  2.  Implement full 64-bit DMA support.  Systems with more than 4GB of RAM
>  can now operate without the cost of bounce buffers.  Cards that cannot do
>  64-bit DMA will automatically revert to using bounce buffers.  This option
>  can be forced off by setting the 'hw.amr.force_sg32" tunable in the loader.
>  It should only be turned off for debugging purposes.  This work was 
>  sponsored
>  by Yahoo.
>  
>  3.  Streamline the command delivery and interrupt handler paths after
>  much discussion with Dell and LSI.  The logic now closely matches the
>  intended design, making it both more robust and much faster.  Certain
>  i/o failures under heavy load should be fixed with this.
>  
>  4.  Optimize the locking.  In the interrupt handler, the card can be 
>  checked
>  for completed commands without any locks held, due to the handler being
>  implicitely serialized and there being no need to look at any shared data.
>  Only grab the lock to return the command structure to the free pool.  A
>  small optimization can still be made to collect all of the completions
>  together and then free them together under a single lock.
>  
>  Items 3 and 4 significantly increase the performance of the driver.  On an
>  LSI 320-2X card, transactions per second went from 13,000 to 31,000 in my
>  testing with these changes.  However, these changes are still fairly
>  experimental and shouldn't be merged to 6.x until there is more testing.
>  
>  Thanks to Doug Ambrosko, LSI, Dell, and Yahoo for contributing towards
>  this.
> 
> 
> 
> 
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-- 
===========================================================================
Scott Mitchell           | PGP Key ID | "Eagles may soar, but weasels
Cambridge, England       | 0x54B171B9 |  don't get sucked into jet engines"
scott at fishballoon.org | 0xAA775B8B |      -- Anon



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