I've noticed a network latency increase. Ping between web server and database : 0.6 ms avg before, 5.3 ms avg after -- it wasn't that big 4 days ago :(
I've narrowed my investigation to one particular "Transaction" in terms of the NewRelic APM. It's basically the main HTTP request of my application. Looks like the ping impacts psycopg2:connect (see http://imgur.com/a/LDH1c): 4 ms up to 16 ms on average. That I can understand. However, I don't understand the performance decrease of the select queries on table1 (see https://i.stack.imgur.com/QaUqy.png): 80 ms up to 160 ms on average Same goes for table 2 (see http://imgur.com/a/CnETs): 4 ms up to 20 ms on average However, there is a commit in my request, and it performs better (see http://imgur.com/a/td8Dc): 12 ms down to 6 ms on average. I don't see how this can be due to network latency! I will provide a new bonnie++ benchmark when the requests per minute is at the lowest (remember I can only run benchmarks while the server is in use). Rick, what did you mean by kernel configuration? The OS is a standard Ubuntu 16.04: - Linux 4.4.0-45-generic #66-Ubuntu SMP Wed Oct 19 14:12:37 UTC 2016 x86_64 x86_64 x86_64 GNU/Linux Do you think losing half the number of cores can explain my performance issue ? (AMD 8 cores down to Haswell 4 cores). Best Regards, Benjamin PS : I've edited the SO post http://serverfault.com/questions/812702/posgres-perf-decreased-although-server-is-better 2016-11-04 1:05 GMT+01:00 Kevin Grittner <kgri...@gmail.com>: > On Thu, Nov 3, 2016 at 9:51 AM, Benjamin Toueg <bto...@gmail.com> wrote: > > > > Stream gives substantially better results with the new server > (before/after) > > Yep, the new server can access RAM at about twice the speed of the old. > > > I've run "bonnie++ -u postgres -d /tmp/ -s 4096M -r 1096" on both > > machines. I don't know how to read bonnie++ results (before/after) > > but it looks quite the same, sometimes better for the new, > > sometimes better for the old. > > On most metrics the new machine looks better, but there are a few > things that look potentially problematic with the new machine: the > new machine uses about 1.57x the CPU time of the old per block > written sequentially ((41 / 143557) / (16 / 87991)); so if the box > becomes CPU starved, you might notice writes getting slower than on > the new box. Also, several of the latency numbers are worse -- in > some cases far worse. If I'm understanding that properly, it > suggests that while total throughput from a number of connections > may be better on the new machine, a single connection may not run > the same query as quickly. That probably makes the new machine > better for handling an OLTP workload from many concurrent clients, > but perhaps not as good at cranking out a single big report or > running dump/restore. > > Yes, it is quite possible that the new machine could be faster at > some things and slower at others. > > -- > Kevin Grittner > EDB: http://www.enterprisedb.com > The Enterprise PostgreSQL Company >
