Hi Mengxing,

Mengxing Liu wrote:
> Hi, Alvaro and Kevin. I'm  Mengxing.  
> This is a “synchronization” email to  tell you what I've done and my next 
> plan. I'm looking forward to your advice. 


> According to my proposal, I want to prepare the experimental environment 
> during the community bonding period. 
> As this is the first time I discuss with Alvaro, here I will introduce the 
> environment again. 
> My lab have a Lenovo System x3950 X6 machine. 
> https://www.lenovo.com/images/products/system-x/pdfs/datasheets/x3950_x6_ds.pdf
> More specifically, there are 8 sockets, each has 15 Intel(R) Xeon(R) CPU 
> E7-8870 v2 @ 2.30GHz. 
> Thus we have 120 cores in total. The storage is a 1 TB SSD, with SAS 
> interface, 500MB write bandwidth. 

OK, having a single disk and 120 CPU cores sounds unbalanced.

> Because we have too many cores, SSD becomes the bottleneck. In my test, 
> pgbench can scale to 36 connections. ( 18 KTPS throughput). CPU utilization 
> is smaller than 30%. 
> Therefore:
> 1. Is there anything wrong in my tuning parameters?For example, should I 
> close "fsync"? Because we don't care recovery here. 

While it's true that we don't care about recovery, I'm not sure that
benchmark results would still be valid with fsync=off.  I would try
synchronous_commit=off instead, and perhaps also enlarge wal_buffers.
What do you have shared_buffers set to?

> 2. Can we use just two sockets (30 physical cores) to run database server? 
> Then the CPU can be the bottleneck so that it  shows the problem we try to 
> solve.

Sure -- it's not a Postgres option, but an operating system option:
you'd set the "maxcpus" parameter in GRUB when booting Linux.
Alternatively, you could use "numactl" to bind the postgres server to a
subset of CPUs.  (And you could put pgbench on a different CPU set).

> >  What method of communication will be used among the mentors and with 
> > Mengxing.
> What method do you prefer?

Mailing list is fine.

> >  Frequency of status updates (must be at least once a week and more often 
> > is encouraged).
> How about reporting my status once a week?

Once a week sounds good to me.

> >  What steps will be taken next during the community bonding period.
> As I wrote in the proposal, I want to establish the environment and read the 
> related source code. Do you have any suggestions for me?

Álvaro Herrera                https://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services

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