Re: [patch] block: make struct block_device cacheline_aligned

[Richard Kennedy <richard@rsk.demon.co.uk>]

On 19/09/12 15:59, Jeff Moyer wrote:
> Jeff Moyer <jmoyer@redhat.com> writes:
> 
>> Hi,
>>
>> When testing against a pcie ssd or a ramdisk, making the block device
>> structure cacheline_aligned provided a significant increase in
>> performance:
> 
> Self-NACK on this one.  This results in a ton of warnings:
> 
> include/linux/fs.h:727: warning: ???__section__??? attribute does not
> apply to types
> In file included from include/linux/debugfs.h:18,
>                  from kernel/trace/trace_probe.h:28,
>                  from kernel/trace/trace_kprobe.c:23:
> include/linux/fs.h:727: warning: ???__section__??? attribute does not
> apply to types
> 
> And that leaves me with the task of figuring out if/why this actually
> helps.
> 
> Cheers,
> Jeff
>>
Hi,
block_device sits in bdev_inode which is already cache line aligned as
they're allocated in a kmem_cache with HWALIGN set.
So I wonder if swapping the order of bdev & inode in bdev_inode will help?

So it becomes this :-
struct bdev_inode {
	struct inode vfs_inode;
	struct block_device bdev;
};


regards
Richard