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SubjectRe: [patch] block: make struct block_device cacheline_aligned
Date
Mikulas Patocka <mpatocka@redhat.com> writes:

> On Wed, 19 Sep 2012, 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
>
> Use ____cacheline_aligned instead of __cacheline_aligned

struct block_device is allocated as part of the bdev_inode:

struct bdev_inode {
struct block_device bdev;
struct inode vfs_inode;
};

The bdev_inode is allocated from the bdev_cachep, which uses
SLAB_HWCACHE_ALIGN. So, in theory, this should already be aligned.

-Jeff


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