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From: Jeff Moyer <jmoyer@redhat.com>
To: Mikulas Patocka <mpatocka@redhat.com>
Cc: Eric Dumazet <eric.dumazet@gmail.com>, Jens Axboe <axboe@kernel.dk>,
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Subject: Re: [PATCH 0/4] Fix a crash when block device is read and block size is changed at the same time
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Date: Tue, 18 Sep 2012 13:22:40 -0400
In-Reply-To: <Pine.LNX.4.64.1209181257410.11735@file.rdu.redhat.com> (Mikulas
	Patocka's message of "Tue, 18 Sep 2012 13:04:58 -0400 (EDT)")
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Mikulas Patocka <mpatocka@redhat.com> writes:

> Hi Jeff
>
> Thanks for testing.
>
> It would be interesting ... what happens if you take the patch 3, leave 
> "struct percpu_rw_semaphore bd_block_size_semaphore" in "struct 
> block_device", but remove any use of the semaphore from fs/block_dev.c? - 
> will the performance be like unpatched kernel or like patch 3? It could be 
> that the change in the alignment affects performance on your CPU too, just 
> differently than on my CPU.

I'll give it a try and report back.

> What is the CPU model that you used for testing?

http://ark.intel.com/products/53570/Intel-Xeon-Processor-E7-2860-%2824M-Cache-2_26-GHz-6_40-GTs-Intel-QPI%29

Cheers,
Jeff