[gem5-users] Re: gem5 : X86 + GCN3 (gfx801) + test_fwd_lrn

[Matt Sinclair via gem5-users]

Hi David,

The dynamic register allocation policy allows the GPU to schedule as many 
wavefronts as there is register space on a CU.  By default, the original 
register allocator released with this GPU model ("simple") only allowed 1 
wavefront per CU at a time because the publicly available dependence modeling 
was fairly primitive.  However, this was not very realistic relative to how a 
real GPU performs, so my group has added better dependence tracking support 
(more could probably still be done, but it reduced stalls by up to 42% relative 
to simple) and a register allocation scheme that allows multiple wavefronts to 
run concurrently per CU ("dynamic").

By default, the GPU model assumes that the simple policy is used unless 
otherwise specified.  I have a patch in progress to change that though: 
https://gem5-review.googlesource.com/c/public/gem5/+/57537.

Regardless, if applications are failing with the simple register allocation 
scheme, I wouldn't expect a more complex scheme to fix the issue.  But I do 
strongly recommend you use the dynamic policy for all experiments - otherwise 
you are using a very simple, less realistic GPU model.

Setting all of that aside, I looked up the perror message you sent last night 
and it appears that happens when your physical machine has run out of memory 
(which means we can't do much to fix gem5, since the machine itself wouldn't 
allocate as much memory as you requested).  So, if you want to run LRN and 
can't run on a machine with more memory, one thing you could do is change the 
LRN config file to use smaller NCHW values (e.g., reduce the batch size, N, 
from 100 to something smaller that fits on your machine): 
https://gem5.googlesource.com/public/gem5-resources/+/refs/heads/develop/src/gpu/DNNMark/config_example/lrn_config.dnnmark#6.
  If you do this though, you will likely need to re-run the generate_cachefile 
to generate the MIOpen binaries for this different sized LRN.

Hope this helps,
Matt

From: David Fong <da...@chronostech.com>
Sent: Tuesday, March 15, 2022 2:58 PM
To: Matt Sinclair <sincl...@cs.wisc.edu>; gem5 users mailing list 
<gem5-users@gem5.org>
Cc: Kyle Roarty <kroa...@wisc.edu>; Poremba, Matthew <matthew.pore...@amd.com>
Subject: RE: gem5 : X86 + GCN3 (gfx801) + test_fwd_lrn

Hi Matt S.,

Thanks for the detailed reply.

I looked at the link you sent me for the weekly run.

I see an additional parameter which I didn't use:

--reg-alloc-policy=dynamic

What does this do ?

I was able to run the two other tests you use in your weekly runs : 
test_fwd_pool, test_bwd_bn
for CUs=4.

David


From: Matt Sinclair <sincl...@cs.wisc.edu<mailto:sincl...@cs.wisc.edu>>
Sent: Monday, March 14, 2022 7:41 PM
To: gem5 users mailing list <gem5-users@gem5.org<mailto:gem5-users@gem5.org>>
Cc: David Fong <da...@chronostech.com<mailto:da...@chronostech.com>>; Kyle 
Roarty <kroa...@wisc.edu<mailto:kroa...@wisc.edu>>; Poremba, Matthew 
<matthew.pore...@amd.com<mailto:matthew.pore...@amd.com>>
Subject: RE: gem5 : X86 + GCN3 (gfx801) + test_fwd_lrn

Hi David,

I have not seen this mmap error before, and my initial guess was the mmap error 
is happening because you are trying to allocate more memory than we created 
when mmap'ing the inputs for the applications (we do this to speed up SE mode, 
because otherwise initializing arrays can take several hours).  However, the 
fact that it is failing in physical.cc and not in the application itself is 
throwing me off there.  Looking at where the failure is occurring, it seems the 
backing store code itself is failing here (from such a large allocation).  
Since the failure is with a C++ mmap call itself, that is perhaps more 
problematic - is "Cannot allocate memory" the failure from the perror() call on 
the line above the fatal() print?

Regarding the other question, and the failures more generally: we have never 
tested with > 64 CUs before, so certainly you are stressing the system and 
encountering different kinds of failures than we have seen previously.

In terms of applications, I had thought most/all of them passed previously, but 
we do not test each and every one all the time because this would make our 
weekly regressions run for a very long time.  You can see here: 
https://gem5.googlesource.com/public/gem5/+/refs/heads/develop/tests/weekly.sh#176<https://urldefense.proofpoint.com/v2/url?u=https-3A__gem5.googlesource.com_public_gem5_-2B_refs_heads_develop_tests_weekly.sh-23176&d=DwMFAg&c=euGZstcaTDllvimEN8b7jXrwqOf-v5A_CdpgnVfiiMM&r=OkH-8nM02VdNPRt_miVO36vI9580zW1SgNQ4MzWRfqc&m=PHGn1HCe8I3xN31ZIG4ubHju1ngyERkZLvihkRk2ZXk&s=19clmMzYHLZtPwMARK0v5V0YZvD3ESFCoS4dnaX_tZo&e=>
 which ones we run on a weekly basis.  I expect all of those to pass (although 
your comment seems to indicate that is not always true?).  Your issues are 
exposing that perhaps we need to test more of them beyond these 3 - perhaps on 
a quarterly basis or something though to avoid inflating the weekly runtime.  
Having said that, I have not run LRN in a long time, as some ML people told me 
that LRN was not widely used anymore.  But when I did run it, I do remember it 
requiring a large amount of memory - which squares with what you are seeing 
here.  I thought LRN needed -mem-size=32 GB to run, but based on your message 
it seems that is not the case.

@Matt P: have you tried LRN lately?  If so, have you run into the same 
OOM/backing store failures?

I know Kyle R. is looking into your other failure, so this one may have to wait 
behind it from our end, unless Matt P knows of a fix.

Thanks,
Matt

From: David Fong via gem5-users 
<gem5-users@gem5.org<mailto:gem5-users@gem5.org>>
Sent: Monday, March 14, 2022 4:38 PM
To: David Fong via gem5-users <gem5-users@gem5.org<mailto:gem5-users@gem5.org>>
Cc: David Fong <da...@chronostech.com<mailto:da...@chronostech.com>>
Subject: [gem5-users] gem5 : X86 + GCN3 (gfx801) + test_fwd_lrn

Hi,

I'm getting an error related to memory for test_fwd_lrn
I increased the memory size from 4GB to 512GB I got memory size issue : "out of 
memory".

build/GCN3_X86/gpu-compute/gpu_compute_driver.cc:599: warn: unimplemented 
ioctl: AMDKFD_IOC_SET_SCRATCH_BACKING_VA
build/GCN3_X86/gpu-compute/gpu_compute_driver.cc:609: warn: unimplemented 
ioctl: AMDKFD_IOC_SET_TRAP_HANDLER
build/GCN3_X86/sim/mem_pool.cc:120: fatal: fatal condition freePages() <= 0 
occurred: Out of memory, please increase size of physical memory.

But once I increased mem size to 1024GB, 1536GB,2048GB I'm getting this DRAM 
device capacity issue.

docker run --rm -v ${PWD}:${PWD} -v 
${PWD}/gem5/gem5-resources/src/gpu/DNNMark/cachefiles:/root/.cache/miopen/2.9.0 
-w ${PWD} gcr.io/gem5-test/gcn-gpu:v21-2 gem5/build/GCN3_X86/gem5.opt 
gem5/configs/example/apu_se.py --mem-size 1536GB --num-compute-units 256 -n3 
--benchmark-root=gem5/gem5-resources/src/gpu/DNNMark/build/benchmarks/test_fwd_lrn
 -cdnnmark_test_fwd_lrn --options="-config 
gem5/gem5-resources/src/gpu/DNNMark/config_example/lrn_config.dnnmark -mmap 
gem5/gem5-resources/src/gpu/DNNMark/mmap.bin" |& tee 
gem5_gpu_cu256_run_dnnmark_test_fwd_lrn_50latency.log
Global frequency set at 1000000000000 ticks per second
build/GCN3_X86/mem/mem_interface.cc:791: warn: DRAM device capacity (8192 
Mbytes) does not match the address range assigned (2097152 Mbytes)
mmap: Cannot allocate memory
build/GCN3_X86/mem/physical.cc:231: fatal: Could not mmap 1649267441664 bytes 
for range [0:0x18000000000]!


Smaller number of CUs like 4 also have same type of error.

Is there a regression script or regression log for DNNMark to show mem-size or 
configurations that are known working for DNNMark tests so
I can use same setup to run a few DNNMark tests?
Only test_fwd_softmax, test_bwd_softmax are working for CUs from 
{4,8,16,32,64,128,256}

Thanks,

David


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