On Fri, Sep 24, 2010 at 8:41 AM, Jens Axboe <jaxboe@xxxxxxxxxxxx> wrote:
>
> [ ... ]
>
> Bart, can you try with this patchset added:
>
> git://git.kernel.dk/linux-2.6-block.git blk-alloc-optimize
>
> It's a work in progress and not suitable for general consumption yet,
> but it's tested working at least. There will be more built on top of
> this, but at least even this simple stuff is making a big difference
> for IOPS testing for me.
Hello Jens,
Thanks for the feedback. I see a nice 10% speedup after having applied
the four block layer optimization patches from the blk-alloc-optimize
branch on an already patched 2.6.35.5 SRP initiator.
Note: according to the output of perf record -g, most spinlock calls
still originate from the block layer. This is what the perf tool
reported for a fio run using libaio with small blocks (512 bytes):
Event: cycles
- 7.06% fio [kernel.kallsyms] [k] _raw_spin_lock_irqsave
- _raw_spin_lock_irqsave
+ 19.51% blk_run_queue
+ 13.71% blk_end_bidi_request
+ 10.04% mlx4_ib_poll_cq
+ 4.68% lock_timer_base
+ 4.22% aio_complete
+ 3.97% srp_send_completion
+ 3.71% srp_queuecommand
+ 3.55% dio_bio_end_aio
+ 3.37% __srp_get_tx_iu
+ 3.14% srp_recv_completion
+ 3.00% scsi_device_unbusy
+ 2.87% __scsi_put_command
+ 2.82% __blockdev_direct_IO_newtrunc
+ 2.76% scsi_put_command
+ 2.69% scsi_run_queue
+ 2.65% dio_bio_submit
+ 2.54% srp_remove_req
+ 2.46% mlx4_ib_post_send
+ 2.33% scsi_get_command
+ 1.95% mlx4_ib_post_recv
[ ... ]
The script I used to generate a patched kernel can be found here
(r2271): https://scst.svn.sourceforge.net/svnroot/scst/trunk/scripts/generate-kernel-with-srp-patches.
Bart.
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