I thought I'd try out what I was in an immediate position to do without having access to dedicated multi-socket hardware: A benchmark on AWS. This was a "c3.8xlarge" instance, which are reportedly backed by Intel Xeon E5-2680 processors. Since the Intel ARK website reports that these CPUs have 16 "threads" (8 cores + hyperthreading), and AWS's marketing material indicates that this instance type has 32 "vCPUs", I inferred that the underlying hardware had 2 sockets. However, reportedly that wasn't the case when procfs was consulted, no doubt due to Xen Hypervisor voodoo:
ubuntu@ip-10-67-128-2:~$ lscpu Architecture: x86_64 CPU op-mode(s): 32-bit, 64-bit Byte Order: Little Endian CPU(s): 32 On-line CPU(s) list: 0-31 Thread(s) per core: 32 Core(s) per socket: 1 Socket(s): 1 NUMA node(s): 1 Vendor ID: GenuineIntel CPU family: 6 Model: 62 Stepping: 4 CPU MHz: 2800.074 BogoMIPS: 5600.14 Hypervisor vendor: Xen Virtualization type: full L1d cache: 32K L1i cache: 32K L2 cache: 256K L3 cache: 25600K NUMA node0 CPU(s): 0-31 I ran the benchmark on Ubuntu 13.10 server, because that seemed to be the only prominent "enterprise" x86_64 AMI (operating system image) that came with GCC 4.8 as part its standard toolchain. This exact setup is benchmarked here: http://www.phoronix.com/scan.php?page=article&item=amazon_ec2_c3&num=1 (Incidentally, some of the other benchmarks on that site use pgbench to benchmark the Linux kernel, filesystems, disks and so on. e.g.: http://www.phoronix.com/scan.php?page=news_item&px=NzI0NQ). I was hesitant to benchmark using a virtualized system. There is a lot of contradictory information about the overhead and/or noise added, which may vary from one workload or hypervisor to the next. But, needs must when the devil drives, and all that. Besides, this kind of setup is very commercially relevant these days, so it doesn't seem unreasonable to see how things work out on an AWS instance that generally performs well for this workload. Of course, I still want to replicate the big improvement you reported for multi-socket systems, but you might have to wait a while for that, unless some kindly benefactor that has a 4 socket server lying around would like to help me out. Results: http://postgres-benchmarks.s3-website-us-east-1.amazonaws.com/c38xlarge-rwlocks/ You can drill down and find the postgresql.conf settings from the report. There appears to be a modest improvement in transaction throughput. It's not as large as the improvement you reported for your 2 socket workstation, but it's there, just about. -- Peter Geoghegan -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
