To make a better testing, I used a third server. This is identical to the centos 7 machine, and it is not included in the replica cluster.
Nobody is accessing this machine, this is top : top - 14:48:36 up 73 days, 17:39, 3 users, load average: 0.00, 0.01, 0.05 Tasks: 686 total, 1 running, 685 sleeping, 0 stopped, 0 zombie %Cpu(s): 0.0 us, 0.0 sy, 0.0 ni,100.0 id, 0.0 wa, 0.0 hi, 0.0 si, 0.0 st KiB Mem : 26383592+total, 1782196 free, 2731144 used, 25932257+buff/cache KiB Swap: 16777212 total, 16298536 free, 478676 used. 21693456+avail Mem These are timings : Time: 2.841 ms Time: 1.980 ms Time: 2.240 ms Time: 2.947 ms Time: 2.828 ms Time: 2.227 ms Time: 1.998 ms Time: 1.990 ms Time: 2.643 ms Time: 2.143 ms Time: 2.919 ms Time: 2.246 ms I never got same results of the centos 6.9 machine. 2017-12-04 15:40 GMT+01:00 Nicola Contu <nicola.co...@gmail.com>: > These are the timings in centos 7 : > > Time: 4.248 ms > Time: 2.983 ms > Time: 3.027 ms > Time: 3.298 ms > Time: 4.420 ms > Time: 2.599 ms > Time: 2.555 ms > Time: 3.008 ms > Time: 6.220 ms > Time: 4.275 ms > Time: 2.841 ms > Time: 3.699 ms > Time: 3.387 ms > > > These are the timings in centos 6: > Time: 1.722 ms > Time: 1.670 ms > Time: 1.843 ms > Time: 1.823 ms > Time: 1.723 ms > Time: 1.724 ms > Time: 1.747 ms > Time: 1.734 ms > Time: 1.764 ms > Time: 1.622 ms > > > This is top on centos 6 : > > [root@****]# top > top - 14:33:32 up 577 days, 23:08, 1 user, load average: 0.16, 0.11, 0.15 > Tasks: 1119 total, 1 running, 1118 sleeping, 0 stopped, 0 zombie > Cpu(s): 0.0%us, 0.1%sy, 0.0%ni, 99.9%id, 0.0%wa, 0.0%hi, 0.0%si, > 0.0%st > Mem: 132040132k total, 129530504k used, 2509628k free, 108084k buffers > Swap: 11665404k total, 331404k used, 11334000k free, 124508916k cached > > This is top on centos 7: > > top - 14:35:38 up 73 days, 19:00, 6 users, load average: 22.46, 20.89, > 20.54 > Tasks: 821 total, 13 running, 807 sleeping, 0 stopped, 1 zombie > %Cpu(s): 14.2 us, 5.0 sy, 0.0 ni, 77.5 id, 3.1 wa, 0.0 hi, 0.2 si, > 0.0 st > KiB Mem : 26383592+total, 4301464 free, 6250384 used, 25328406+buff/cache > KiB Swap: 16777212 total, 11798876 free, 4978336 used. 24497036+avail Mem > > > The production machine is obviously more accessed. But that does not seem > to be the problem as running the same query on the replica of the > production machine (same config of the master but not accessed by anyone) > gives the same bad result: > Time: 6.366 ms > > > 2017-12-04 15:19 GMT+01:00 Chris Mair <ch...@1006.org>: > >> centos 7 : >>> Time: 3.884 ms >>> >>> centos 6.9 >>> >> Time: 1.620 ms >> >>> >>> >>> Is there anything you can advice to solve or identify the problem? >>> >> >> Can you run this query 10 times on each server and note the timings? >> >> I'd like to see the reproducability of this. >> >> Also: both machines are otherwise idle (check with top or uptime)? >> >> Bye, >> Chris. >> >> >> >
