[SPDK] performance of rocksdb on blobfs

Harris, James R james.r.harris at intel.com
Thu May 4 10:06:10 PDT 2017


> On May 3, 2017, at 10:04 PM, Liu, Yun1 <yun1.liu at intel.com> wrote:
> 
> 
> I've tried db_bench in the rocksdb on blobfs, but didn't get performance improvement as expected.
> Compared with NO_SPDK, insert increased 70%, readwrite increased 28%, but overwrite decreased 38%, randread decreased 48%.
> (the attached pic is the detail results.)
> Is it a normal result or is there a way that we can get a better result by adjusting some parameters?
> 
> PS, here are the environment:
> Storage: P3700, OS: CentOS 7.3, gcc: 6.3, Keys: 16B, Values: 1000B, Entries: 500M

Hi Yun,

This is not the expected result.

Can you confirm a few pieces of data for me:

1) FW revision on your P3700.  Recommendation is to have FW version 1H0 or greater (look at last three digits in FW version).  TRIM performance especially is much better with more recent versions of P3700 FW and helps blobfs performance more than kernel/XFS performance (even with mount -o discard).  This would not explain randread performance differences (since randread does not drive any compaction which means no file deletions) but could affect overwrite performance.
2) What size of SPDK blobfs cache are you using for your tests?  Note that the kernel (NO_SPDK) case will use as much memory as possible for page cache, while SPDK blobfs will be restricted to the amount specified.  The run_test.sh script will override the default 4GB blobfs cache by specifying a larger value in the CACHE_SIZE environment variable which is specified in terms of MB.  So CACHE_SIZE=16384 ./run_test.sh will use 16GB of cache for blobfs.  Again this would likely affect performance more for the overwrite case, where compaction drives blobfs cache usage with flush and compaction operations.
3) Can you describe the CPU/platform you are running on?

Thanks,

-Jim



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