block: improve struct request_queue layout

It's clearly been a while since someone looked at this, so I gave it a
quick shot. There are few issues in here:

- Random bundling of members that are mostly read-only and often written
- Random holes that need not be there

This moves the most frequently used bits into cacheline 1 and 2, with
the 2nd one being more write intensive than the first one, which is
basically read-only.

Outside of making this work a bit more efficiently, it also reduces the
size of struct request_queue for my test setup from 864 bytes (spanning
14 cachelines!) to 832 bytes and 13 cachelines.

Reviewed-by: Christoph Hellwig <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Jens Axboe <[email protected]>

0 files changed, 0 insertions, 0 deletions