Re: [PATCH] qla2xxx: Resolved a performance issue in interrupt handler

Matthew Wilcox
2009-06-10T16:18:26Z

On Wed, Jun 10, 2009 at 09:09:14AM -0700, Anirban Chakraborty wrote:
>
> On Jun 10, 2009, at 8:52 AM, Styner, Douglas W wrote:
>
>>
>> Anirban Chakraborty [mailto:anirban.chakraborty@qlogic.com] write:
>>>
>>> You got it right. Basically we are doing:
>>> 1. baseline scsi-misc + earlier patch
>>> 2. baseline scsi-misc + this patch
>>> And then compare 1 and 2.
>>
>> Results are as follows:
>> Total interrupts are down slightly (-0.8%), QLA interrupts are flat
>> (-0.1%) Cycles for qla2xxx_intr_handler up from .77% to .92%.
>
> So, it looks like using spin_lock_irqsave is doing a better job than
> globally disabling the sharing of the interrupt via IRQF_DISABLED.

The margin of error for this setup is about 0.3% for the performance
as a whole. I don't know what the margin of error is for the number
of cycles consumed by a given function, but I would suspect it's
significantly higher than the 0.15% difference seen.

>> ======oprofile CPU_CLK_UNHALTED for top 30 functions
>> Cycles% 2.6.30-rc6_scsi-misc_0001 Cycles% 2.6.30-rc6_scsi-misc_irqf-d
>> 68.1402 <database> 66.1875 <database>
>> 0.9125 qla24xx_start_scsi 0.9552 qla24xx_start_scsi
>> 0.8729 __schedule 0.9272 __schedule
>> 0.7739 qla24xx_intr_handler 0.9178 qla24xx_intr_handler
>> 0.7161 kmem_cache_alloc 0.7963 kmem_cache_alloc
>> 0.4686 __sigsetjmp 0.4580 __sigsetjmp
>> 0.4043 __blockdev_direct_IO 0.4206 __switch_to
>> 0.3894 __switch_to 0.4169 __blockdev_direct_IO
>> 0.3878 rb_get_reader_page 0.3907 scsi_request_fn
>> 0.3762 task_rq_lock 0.3776 task_rq_lock
>> 0.3729 scsi_request_fn 0.3701 rb_get_reader_page
>> 0.3696 __list_add 0.3664 __list_add
>> 0.3168 <bash> 0.3664 copy_user_generic_string
>> 0.3135 try_to_wake_up 0.3122 lock_timer_base
>> 0.2921 ring_buffer_consume 0.2972 ring_buffer_consume
>> 0.2822 lock_timer_base 0.2879 <bash>
>> 0.2624 memset_c 0.2785 aio_complete
>> 0.2607 aio_complete 0.2524 blk_queue_end_tag
>> 0.2508 copy_user_generic_string 0.2468 try_to_wake_up
>> 0.2294 qla2x00_process_completed_re 0.2430 tcp_sendmsg
>> 0.2294 tcp_sendmsg 0.2393 mod_timer
>> 0.2211 kfree 0.2374 qla2x00_process_completed_re
>> 0.2195 memmove 0.2355 memset_c
>> 0.2195 blk_queue_end_tag 0.2225 e1000_xmit_frame
>> 0.2145 scsi_softirq_done 0.2094 generic_make_request
>> 0.2145 mod_timer 0.2075 scsi_device_unbusy
>> 0.2129 generic_file_aio_read 0.2056 kref_get
>> 0.2096 kref_get 0.2056 mempool_free
>> 0.1997 e1000_xmit_frame 0.2038 qla2xxx_queuecommand
>> 0.1997 scsi_device_unbusy 0.2000 kfree
>
> --
> To unsubscribe from this list: send the line "unsubscribe linux-scsi" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at http://vger.kernel.org/majordomo-info.html

--
Matthew Wilcox Intel Open Source Technology Centre
"Bill, look, we understand that you're interested in selling us this
operating system, but compare it to ours. We can't possibly take such
a retrograde step."