Re: [dm-devel] [PATCH 0/4] Fix a crash when block device is read and block size is changed at the same time

[Jeff Moyer <jmoyer redhat com>]

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