[Scst-devel] [ofa-general] SRP/mlx4 interrupts throttling performance

[Vladislav Bolkhovitin]

Cameron Harr, on 01/28/2009 10:58 PM wrote:
> I've attached a spreadsheet with some of my findings. In the Summary 
> tab, I have a baseline with no affinity set. For other 5 tests, see below.
> 
> Vladislav Bolkhovitin wrote:
>> Try the following variants:
>>
>> 1. Affine IRQ 82, scsi_tgt0 to CPU0, fct0-worker to CPU2, IRQs 169 and 
>> 177 to CPU4, scsi_tgt1 to CPU1, fct1-worker to CPU3, scsi_tgt2 to 
>> CPU5, fct2-worker to CPU7
>>
>> 2. Affine IRQ 82 to CPU0, fct0-worker to CPU2, IRQs 169 and 177 to 
>> CPU4, fct1-worker to CPU3, fct2-worker to CPU7, no affinity for other 
>> processes.
>>
>> 3. Affine IRQ 82 to CPU0, IRQs 169 and 177 to CPU4, fct1-worker's to 
>> all CPUs, except CPU0 and CPU4, no affinity for other processes.
> These are tests 1, 2 and 3, respectively
>> Or other similar variants you'd like (even CPUs relate to physical 
>> CPU0, odd CPUs relate to physical CPU1). For instance, you can try to 
>> affine IRQs 169 and 177 to CPU1.
> I did two other tests (Tests 4,5), that has the mlx4_core (comp) IRQ 
> (formerly known as IRQ 82) pinned to CPU0, the two ioDrive IRQs (169, 
> 177) pinned to CPU 4, fct0 and scsi_tgt0 on CPUs 2&3, fct1 and scsi_tgt1 
> on CPUs 4&6 (test 4) OR fct1 and scsi_tgt1 on CPUs 5&6.
>> No points to run for srptthread=1, for it just produce a baseline with 
>> no affinity at all.
> I ran with these anyway to look at differences among the tests. Having 
> this thread enabled always results in better performance.
>> Please do each run several times and write down an average result 
>> between runs and approximate variation between them in %%. Otherwise 
>> we can't make any reliable conclusions.
> I ran each test 3 times and took the averages. In order to get a quick 
> look at performance per run, I added a column in the summary that sums 
> the IOPs for each test with SRPT thread enabled and then not enabled. 
> Test 4 seems to give the best results. Here's a brief summary of that 
> summary with just SRPT thread=0:
> 
> Baseline: 356226.39
> Test 1:   371217.6533
> Test 2:   370553.78
> Test 3:   373295.2033
> Test 4:   399385.2233
> Test 5:   393204.5833

Linux CPU scheduler does really impressive job!

Interesting, will something change with:

1. The latest SVN. It has some changes, which might make a difference.

2. Pass-through dev handler instead of BLOCKIO, which you are using.

Thanks,
Vlad