[gpfsug-discuss] bizarre performance behavior

Thu May 4 14:22:25 BST 2017

Hi,

We found out using ib_read_bw and ib_write_bw that there were some links 
between server and clients degraded, having a bandwith of 350MB/s

strangely, nsdperf did not report the same. It reported 12GB/s write and 
9GB/s read, which was much more then we actually could achieve.

So the problem was some bad ib routing. We changed some ib links, and 
then we got also 12GB/s read with nsdperf.

On our clients we then are able to achieve the 7,2GB/s in total we also 
saw using the nsd servers!

Many thanks for the help !!

We are now running some tests with different blocksizes and parameters, 
because our backend storage is able to do more than the 7.2GB/s we get 
with GPFS (more like 14GB/s in total). I guess prefetchthreads and 
nsdworkerthreads are the ones to look at?

Cheers!

Kenneth

On 21/04/17 22:27, Kumaran Rajaram wrote:
> Hi Kenneth,
>
> As it was mentioned earlier, it will be good to first verify the raw 
> network performance between the NSD client and NSD server using the 
> nsdperf tool that is built with RDMA support.
> g++ -O2 -DRDMA -o nsdperf -lpthread -lrt -libverbs -lrdmacm nsdperf.C
>
> In addition, since you have 2 x NSD servers it will be good to perform 
> NSD client  file-system performance test with just single NSD server 
> (mmshutdown the other server, assuming all the NSDs have primary, 
> server NSD server configured + Quorum will be intact when a NSD server 
> is brought down) to see if it helps to improve the read performance + 
> if there are variations in the file-system read bandwidth results 
> between NSD_server#1 'active' vs. NSD_server #2 'active' (with other 
> NSD server in GPFS "down" state). If there is significant variation, 
> it can help to isolate the issue to particular NSD server (HW or IB 
> issue?).
>
> You can issue "mmdiag --waiters" on NSD client as well as NSD servers 
> during your dd test, to verify if there are unsual long GPFS waiters. 
> In addition, you may issue Linux  "perf top -z" command on the GPFS 
> node  to see if there is  high CPU usage by any particular call/event 
> (for e.g., If GPFS config parameter verbsRdmaMaxSendBytes has been 
>  set to low value from the default 16M, then it can cause RDMA 
> completion threads to go CPU bound ). Please verify some performance 
> scenarios detailed in Chapter 22 in Spectrum Scale Problem 
> Determination Guide (link below).
>
> https://www.ibm.com/support/knowledgecenter/en/STXKQY_4.2.3/com.ibm.spectrum.scale.v4r23.doc/pdf/scale_pdg.pdf?view=kc
>
> Thanks,
> -Kums
>
>
>
>
>
> From: Kenneth Waegeman <kenneth.waegeman at ugent.be>
> To: gpfsug main discussion list <gpfsug-discuss at spectrumscale.org>
> Date: 04/21/2017 11:43 AM
> Subject: Re: [gpfsug-discuss] bizarre performance behavior
> Sent by: gpfsug-discuss-bounces at spectrumscale.org
> ------------------------------------------------------------------------
>
>
>
> Hi,
>
> We already verified this on our nsds:
>
> [root at nsd00 ~]# /opt/dell/toolkit/bin/syscfg --QpiSpeed
> QpiSpeed=maxdatarate
> [root at nsd00 ~]# /opt/dell/toolkit/bin/syscfg --turbomode
> turbomode=enable
> [root at nsd00 ~]# /opt/dell/toolkit/bin/syscfg –-SysProfile
> SysProfile=perfoptimized
>
> so sadly this is not the issue.
>
> Also the output of the verbs commands look ok, there are connections 
> from the client to the nsds are there is data being read and writen.
>
> Thanks again!
>
> Kenneth
>
>
> On 21/04/17 16:01, Kumaran Rajaram wrote:
> Hi,
>
> Try enabling the following in the BIOS of the NSD servers (screen 
> shots below)
>
>   * Turbo Mode - Enable
>   * QPI Link Frequency - Max Performance
>   * Operating Mode - Maximum Performance
>   * >>>>While we have even better performance with sequential reads on
>     raw storage LUNS, using GPFS we can only reach 1GB/s in total
>     (each nsd server seems limited by 0,5GB/s) independent of the
>     number of clients
>
>     >>We are testing from 2 testing machines connected to the nsds
>     with infiniband, verbs enabled.
>
>
> Also, It will be good to verify that all the GPFS nodes have Verbs 
> RDMA started using "mmfsadm test verbs status" and that the NSD 
> client-server communication from client to server during "dd" is 
> actually using Verbs RDMA using "mmfsadm test verbs conn" command  (on 
> NSD client doing dd). If not, then GPFS might be using TCP/IP network 
> over which the cluster is configured impacting performance (If this is 
> the case, GPFS mmfs.log.latest for any Verbs RDMA related errors and 
> resolve).
>
>  *
>
>
>
>
>
>
> Regards,
> -Kums
>
>
>
>
>
>
> From: "Knister, Aaron S. (GSFC-606.2)[COMPUTER SCIENCE CORP]" 
> _<aaron.s.knister at nasa.gov>_ <mailto:aaron.s.knister at nasa.gov>
> To: gpfsug main discussion list _<gpfsug-discuss at spectrumscale.org>_ 
> <mailto:gpfsug-discuss at spectrumscale.org>
> Date: 04/21/2017 09:11 AM
> Subject: Re: [gpfsug-discuss] bizarre performance behavior
> Sent by: _gpfsug-discuss-bounces at spectrumscale.org_ 
> <mailto:gpfsug-discuss-bounces at spectrumscale.org>
> ------------------------------------------------------------------------
>
>
>
> Fantastic news! It might also be worth running "cpupower monitor" or 
> "turbostat" on your NSD servers while you're running dd tests from the 
> clients to see what CPU frequency your cores are actually running at.
>
> A typical NSD server workload (especially with IB verbs and for reads) 
> can be pretty light on CPU which might not prompt your CPU crew 
> governor to up the frequency (which can affect throughout). If your 
> frequency scaling governor isn't kicking up the frequency of your CPUs 
> I've seen that cause this behavior in my testing.
>
> -Aaron
>
>
>
>
> On April 21, 2017 at 05:43:40 EDT, Kenneth Waegeman 
> _<kenneth.waegeman at ugent.be>_ <mailto:kenneth.waegeman at ugent.be>wrote:
>
> Hi,
>
> We are running a test setup with 2 NSD Servers backed by 4 Dell 
> Powervaults MD3460s. nsd00 is primary serving LUNS of controller A of 
> the 4 powervaults, nsd02 is primary serving LUNS of controller B.
>
> We are testing from 2 testing machines connected to the nsds with 
> infiniband, verbs enabled.
>
> When we do dd from the NSD servers, we see indeed performance going to 
> 5.8GB/s for one nsd, 7.2GB/s for the two! So it looks like GPFS is 
> able to get the data at a decent speed. Since we can write from the 
> clients at a good speed, I didn't suspect the communication between 
> clients and nsds being the issue, especially since total performance 
> stays the same using 1 or multiple clients.
>
> I'll use the nsdperf tool to see if we can find anything,
>
> thanks!
>
> K
>
> On 20/04/17 17:04, Knister, Aaron S. (GSFC-606.2)[COMPUTER SCIENCE 
> CORP] wrote:
> Interesting. Could you share a little more about your architecture? Is 
> it possible to mount the fs on an NSD server and do some dd's from the 
> fs on the NSD server? If that gives you decent performance perhaps try 
> NSDPERF next 
> _https://www.ibm.com/developerworks/community/wikis/home?lang=en#!/wiki/General+Parallel+File+System+(GPFS)/page/Testing+network+performance+with+nsdperf_ 
> <https://www.ibm.com/developerworks/community/wikis/home?lang=en#%21/wiki/General+Parallel+File+System+%28GPFS%29/page/Testing+network+performance+with+nsdperf>
>
> -Aaron
>
>
>
>
> On April 20, 2017 at 10:53:47 EDT, Kenneth Waegeman 
> _<kenneth.waegeman at ugent.be>_ <mailto:kenneth.waegeman at ugent.be>wrote:
>
> Hi,
>
> Having an issue that looks the same as this one:
>
> We can do sequential writes to the filesystem at 7,8 GB/s total , 
> which is the expected speed for our current storage
> backend.  While we have even better performance with sequential reads 
> on raw storage LUNS, using GPFS we can only reach 1GB/s in total (each 
> nsd server seems limited by 0,5GB/s) independent of the number of clients
> (1,2,4,..) or ways we tested (fio,dd). We played with blockdev params, 
> MaxMBps, PrefetchThreads, hyperthreading, c1e/cstates, .. as discussed 
> in this thread, but nothing seems to impact this read performance.
>
> Any ideas?
>
> Thanks!
>
> Kenneth
>
> On 17/02/17 19:29, Jan-Frode Myklebust wrote:
> I just had a similar experience from a sandisk infiniflash system 
> SAS-attached to s single host. Gpfsperf reported 3,2 Gbyte/s for 
> writes. and 250-300 Mbyte/s on sequential reads!! Random reads were on 
> the order of 2 Gbyte/s.
>
> After a bit head scratching snd fumbling around I found out that 
> reducing maxMBpS from 10000 to 100 fixed the problem! Digging further 
> I found that reducing prefetchThreads from default=72 to 32 also fixed 
> it, while leaving maxMBpS at 10000. Can now also read at 3,2 GByte/s.
>
> Could something like this be the problem on your box as well?
>
>
>
> -jf
> fre. 17. feb. 2017 kl. 18.13 skrev Aaron Knister 
> <_aaron.s.knister at nasa.gov_ <mailto:aaron.s.knister at nasa.gov>>:
> Well, I'm somewhat scrounging for hardware. This is in our test
> environment :) And yep, it's got the 2U gpu-tray in it although even
> without the riser it has 2 PCIe slots onboard (excluding the on-board
> dual-port mezz card) so I think it would make a fine NSD server even
> without the riser.
>
> -Aaron
>
> On 2/17/17 11:43 AM, Simon Thompson (Research Computing - IT Services)
> wrote:
> > Maybe its related to interrupt handlers somehow? You drive the load 
> up on one socket, you push all the interrupt handling to the other 
> socket where the fabric card is attached?
> >
> > Dunno ... (Though I am intrigued you use idataplex nodes as NSD 
> servers, I assume its some 2U gpu-tray riser one or something !)
> >
> > Simon
> > ________________________________________
> > From: _gpfsug-discuss-bounces at spectrumscale.org_ 
> <mailto:gpfsug-discuss-bounces at spectrumscale.org>[_gpfsug-discuss-bounces at spectrumscale.org_ 
> <mailto:gpfsug-discuss-bounces at spectrumscale.org>] on behalf of Aaron 
> Knister [_aaron.s.knister at nasa.gov_ <mailto:aaron.s.knister at nasa.gov>]
> > Sent: 17 February 2017 15:52
> > To: gpfsug main discussion list
> > Subject: [gpfsug-discuss] bizarre performance behavior
> >
> > This is a good one. I've got an NSD server with 4x 16GB fibre
> > connections coming in and 1x FDR10 and 1x QDR connection going out to
> > the clients. I was having a really hard time getting anything resembling
> > sensible performance out of it (4-5Gb/s writes but maybe 1.2Gb/s for
> > reads). The back-end is a DDN SFA12K and I *know* it can do better than
> > that.
> >
> > I don't remember quite how I figured this out but simply by running
> > "openssl speed -multi 16" on the nsd server to drive up the load I saw
> > an almost 4x performance jump which is pretty much goes against every
> > sysadmin fiber in me (i.e. "drive up the cpu load with unrelated crap to
> > quadruple your i/o performance").
> >
> > This feels like some type of C-states frequency scaling shenanigans that
> > I haven't quite ironed down yet. I booted the box with the following
> > kernel parameters "intel_idle.max_cstate=0 processor.max_cstate=0" which
> > didn't seem to make much of a difference. I also tried setting the
> > frequency governer to userspace and setting the minimum frequency to
> > 2.6ghz (it's a 2.6ghz cpu). None of that really matters-- I still have
> > to run something to drive up the CPU load and then performance improves.
> >
> > I'm wondering if this could be an issue with the C1E state? I'm curious
> > if anyone has seen anything like this. The node is a dx360 M4
> > (Sandybridge) with 16 2.6GHz cores and 32GB of RAM.
> >
> > -Aaron
> >
> > --
> > Aaron Knister
> > NASA Center for Climate Simulation (Code 606.2)
> > Goddard Space Flight Center
> > (301) 286-2776
> > _______________________________________________
> > gpfsug-discuss mailing list
> > gpfsug-discuss at _spectrumscale.org_ <http://spectrumscale.org/>
> > _http://gpfsug.org/mailman/listinfo/gpfsug-discuss_
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> >
>
> --
> Aaron Knister
> NASA Center for Climate Simulation (Code 606.2)
> Goddard Space Flight Center
> (301) 286-2776
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