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Changing to the acpi_idle driver dropped the performance by about 50%. That was an unexpected result.
I'm having issues with powertop and the userspace governor, it always shows 100% idle. I downloaded the latest version with the same result. Still more work to do, but wanted to share my findings.
- ----------------
Robert LeBlanc
PGP Fingerprint 79A2 9CA4 6CC4 45DD A904 C70E E654 3BB2 FA62 B9F1
On Wed, Sep 2, 2015 at 9:50 AM, Robert LeBlanc wrote:
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Thanks for the responses.
I forgot to include the fio test for completeness:
8 job QD=8
[ext4-test]
runtime=150
name=ext4-test
readwrite=randrw
size=15G
blocksize=4k
ioengine=sync
iodepth=8
numjobs=8
thread
group_reporting
time_based
direct=1
1 job QD=1
[ext4-test]
runtime=150
name=ext4-test
readwrite=randrw
size=15G
blocksize=4k
ioengine=sync
iodepth=1
numjobs=1
thread
group_reporting
time_based
direct=1
I have not disabled all of the power management, I've only prevented the CPU from going to an idle state below C1. I'll have to check on Jan's suggestion of swapping out the intel_idle driver to see what difference it makes. I did not run powertop as I did the testing because it (or cpupower monitor) impacted performance and would have thrown off the results. I'll do some runs with lower clocks and make sure that it is staying at the lower speeds. Here is some additional output:
# cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_governor
userspace
# cpupower monitor
|Nehalem || Mperf || Idle_Stats
CPU | C3 | C6 | PC3 | PC6 || C0 | Cx | Freq || POLL | C1-A | C6-A
0| 0.00| 94.19| 0.00| 0.00|| 5.70| 94.30| 1299|| 0.00| 0.00| 94.32
1| 0.00| 99.39| 0.00| 0.00|| 0.53| 99.47| 1298|| 0.00| 0.00| 99.48
2| 0.00| 99.60| 0.00| 0.00|| 0.38| 99.62| 1299|| 0.00| 0.00| 99.61
3| 0.00| 99.63| 0.00| 0.00|| 0.36| 99.64| 1299|| 0.00| 0.00| 99.64
4| 0.00| 99.84| 0.00| 0.00|| 0.11| 99.89| 1301|| 0.00| 0.00| 99.97
5| 0.00| 99.57| 0.00| 0.00|| 0.40| 99.60| 1299|| 0.00| 0.00| 99.61
6| 0.00| 99.72| 0.00| 0.00|| 0.27| 99.73| 1299|| 0.00| 0.00| 99.73
7| 0.00| 99.98| 0.00| 0.00|| 0.01| 99.99| 1321|| 0.00| 0.00| 99.99
# cat /sys/devices/system/cpu/cpuidle/current_driver
intel_idle
I then echo "1" into /dev/cpu_dma_latency. We can see that the idle time moves from C6 to C1
# cpupower monitor
|Nehalem || Mperf || Idle_Stats
CPU | C3 | C6 | PC3 | PC6 || C0 | Cx | Freq || POLL | C1-A | C6-A
0| 0.00| 0.00| 0.00| 0.00|| 0.37| 99.63| 1299|| 0.00| 99.63| 0.00
1| 0.00| 0.00| 0.00| 0.00|| 0.16| 99.84| 1299|| 0.00| 99.84| 0.00
2| 0.00| 0.00| 0.00| 0.00|| 0.47| 99.53| 1299|| 0.00| 99.53| 0.00
3| 0.00| 0.00| 0.00| 0.00|| 0.43| 99.57| 1299|| 0.00| 99.57| 0.00
4| 0.00| 0.00| 0.00| 0.00|| 0.09| 99.91| 1300|| 0.00| 99.91| 0.00
5| 0.00| 0.00| 0.00| 0.00|| 0.06| 99.94| 1298|| 0.00| 99.94| 0.00
6| 0.00| 0.00| 0.00| 0.00|| 0.09| 99.91| 1300|| 0.00| 99.91| 0.00
7| 0.00| 0.00| 0.00| 0.00|| 0.28| 99.72| 1299|| 0.00| 99.72| 0.00
# cat /sys/devices/system/cpu/cpu0/cpuidle/state*/latency
0
2
15
# cat /sys/devices/system/cpu/cpu*/cpufreq/scaling_{min,max,cur}_freq
1200000
1200000
1200000
1200000
1200000
1200000
1200000
1200000
1200000
2401000
2401000
2401000
2401000
2401000
2401000
2401000
1200000
1200000
1200000
1600000
1200000
1200000
1200000
1200000
Thanks for taking the time to collaborate with me on this.
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- ----------------
Robert LeBlanc
PGP Fingerprint 79A2 9CA4 6CC4 45DD A904 C70E E654 3BB2 FA62 B9F1
On Wed, Sep 2, 2015 at 3:21 AM, Nick Fisk wrote:
I think this may be related to what I had to do, it rings a bell at least.
http://unix.stackexchange.com/questions/153693/cant-use-userspace-cpufreq-governor-and-set-cpu-frequency
The P-state drive doesn't support userspace, so you need to disable it and make Linux use the old acpi drive instead.
> -----Original Message-----
> From: Nick Fisk [mailto:nick@xxxxxxxxxx]
> Sent: 01 September 2015 22:21
> To: 'Robert LeBlanc'
> Cc: ceph-users@xxxxxxxxxxxxxx
> Subject: RE: Ceph SSD CPU Frequency Benchmarks
>
> > -----Original Message-----
> > From: ceph-users [mailto:ceph-users-bounces@xxxxxxxxxxxxxx] On Behalf
> > Of Robert LeBlanc
> > Sent: 01 September 2015 21:48
> > To: Nick Fisk
> > Cc: ceph-users@xxxxxxxxxxxxxx
> > Subject: Re: Ceph SSD CPU Frequency Benchmarks
> >
> > -----BEGIN PGP SIGNED MESSAGE-----
> > Hash: SHA256
> >
> > Nick,
> >
> > I've been trying to replicate your results without success. Can you
> > help me understand what I'm doing that is not the same as your test?
> >
> > My setup is two boxes, one is a client and the other is a server. The
> > server has Intel(R) Atom(TM) CPU C2750 @ 2.40GHz, 32 GB RAM and 2
> > Intel S3500
> > 240 GB SSD drives. The boxes have Infiniband FDR cards connected to a
> > QDR switch using IPoIB. I set up OSDs on the 2 SSDs and set pool
> > size=1. I mapped a 200GB RBD using the kernel module ran fio on the
> > RBD. I adjusted the number of cores, clock speed and C-states of the
> > server and here are my
> > results:
> >
> > Adjusted core number and set the processor to a set frequency using
> > the userspace governor.
> >
> > 8 jobs 8 depth Cores
> > 1 2 3 4 5 6 7 8
> > Frequency 2.4 387 762 1121 1432 1657 1900 2092 2260
> > GHz 2 386 758 1126 1428 1657 1890 2090 2232
> > 1.6 382 756 1127 1428 1656 1894 2083 2201
> > 1.2 385 756 1125 1431 1656 1885 2093 2244
> >
>
> I tested at QD=1 as this tends to highlight the difference in clock speed,
> whereas a higher queue depth will probably scale with both frequency and
> cores. I'm not sure this is your problem, but to make sure your environment
> is doing what you want I would suggest QD=1 and 1 job to start with.
>
> But thank you for sharing these results regardless of your current frequency
> scaling issues. Information like this is really useful for people trying to decide
> on hardware purchases. Those Atom boards look like they could support 12x
> normal HDD's quite happily, assuming 80 IOPsx12.
>
> I wonder if we can get enough data from various people to generate a
> IOPs/CPU Freq for various CPU architectures?
>
>
> > I then adjusted the processor to not go in a deeper sleep state than
> > C1 and also tested setting the highest CPU frequency with the ondemand
> governor.
> >
> > 1 job 1 depth
> > Cores 1
> > <=C1, feq range C0-C6, freq range C0-C6, static freq <=C1, static
> > freq
> > Frequency 2.4 381 381 379 381
> > GHz 2 382 380 381 381
> > 1.6 380 381 379 382
> > 1.2 383 378 379 383
> > Cores 8
> > <=C1, feq range C0-C6, freq range C0-C6, static freq <=C1, static
> > freq
> > Frequency 2.4 629 580 584 629
> > GHz 2 630 579 584 634
> > 1.6 630 579 584 634
> > 1.2 632 581 582 634
> >
> > Here I'm see a correlation between # cores and C-states, but not
> frequency.
> >
> > Frequency was controlled with:
> > cpupower frequency-set -d 1.2GHz -u 1.2GHz -g userspace and cpupower
> > frequency-set -d 1.2GHz -u 2.0GHz -g ondemand
> >
> > Core count adjusted by:
> > for i in {1..7}; do echo 0 > /sys/devices/system/cpu/cpu$i/online;
> > done
> >
> > C-states controlled by:
> > # python
> > Python 2.7.5 (default, Jun 24 2015, 00:41:19) [GCC 4.8.3 20140911 (Red
> > Hat 4.8.3-9)] on linux2 Type "help", "copyright", "credits" or
> > "license" for more information.
> > >>> fd = open('/dev/cpu_dma_latency','wb')
> > >>> fd.write('1')
> > >>> fd.flush()
> > >>> fd.close() # Don't run this until the tests are completed (the
> > >>> handle has
> > to stay open).
> > >>>
> >
> > I'd like to replicate your results. I'd also like if you can verify
> > some of mine in your set-up around C-States and cores.
>
> I can't remember exactly, but I think I had to do something to get the
> userspace governor to behave as I expected it to. I tend to recall setting the
> frequency low and yet still seeing it bursting up to max. I will have a look
> through my notes tomorrow and see if I can recall anything. One thing I do
> remember though is that the Intel powertop utility was very useful in
> confirming what the actual CPU frequency was. It might be worth installing
> and running this and seeing what the CPU cores are doing.
>
>
> >
> > Thanks,
> >
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> >
> > ----------------
> > Robert LeBlanc
> > PGP Fingerprint 79A2 9CA4 6CC4 45DD A904 C70E E654 3BB2 FA62 B9F1
> >
> > On Sat, Jun 13, 2015 at 8:58 AM, Nick Fisk wrote:
> > Hi All,
> >
> > I know there has been lots of discussions around needing fast CPU's to
> > get the most out of SSD's. However I have never really ever seen an
> > solid numbers to make a comparison about how much difference a faster
> > CPU makes and if Ceph scales linearly with clockspeed. So I did a
> > little experiment today.
> >
> > I setup a 1 OSD Ceph instance on a Desktop PC. The Desktop has a i5
> > Sandbybridge CPU with the CPU turbo overclocked to 4.3ghz. By using
> > the userspace governor in Linux, I was able to set static clock speeds
> > to see the possible performance effects on Ceph. My pc only has an old
> > X25M-G2 SSD, so I had to limit the IO testing to 4kb QD=1, as
> > otherwise the SSD ran out of puff when I got to the higher clock
> > speeds.
> >
> > CPU Mhz 4Kb Write IO Min Latency (us) Avg Latency (us) CPU
> > usr CPU sys
> > 1600 797 886 1250
> > 10.14 2.35
> > 2000 815 746 1222
> > 8.45 1.82
> > 2400 1161 630 857
> > 9.5 1.6
> > 2800 1227 549 812
> > 8.74 1.24
> > 3300 1320 482 755
> > 7.87 1.08
> > 4300 1548 437 644
> > 7.72 0.9
> >
> > The figures show a fairly linear trend right through the clock range
> > and clearly shows the importance of having fast CPU's (Ghz not cores)
> > if you want to achieve high IO, especially at low queue depths.
> >
> >
> > Things to Note
> > These figures are from a desktop CPU, no doubt Xeons will be slightly
> > faster at the same clock speed I assuming using the userspace governor
> > in this way is a realistic way to simulate different CPU clock speeds?
> > My old SSD is probably skewing the figures slightly I have complete
> > control over the turbo settings and big cooling, many server CPU's
> > will limit the max turbo if multiple cores are under load or get too
> > hot Ceph SSD OSD nodes are probably best with high end E3 CPU's as
> > they have the highest clock speeds HDD's with Journals will probably
> > benefit slightly from higher clock speeds, if the disk isn't the
> > bottleneck (ie small block sequential writes) These numbers are for
> > Replica=1, at 2 or 3 these numbers will be at least half I would
> > imagine
> >
> >
> > I hope someone finds this useful
> >
> > Nick
> >
> >
> >
> >
> > _______________________________________________
> > ceph-users mailing list
> > ceph-users@xxxxxxxxxxxxxx
> > http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
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