| Hi there, I’m running PostgreSQL 9.6.2 on Ubuntu 16.04.2 TLS (kernel 4.4.0-66-generic). Hardware is: - 2 x Intel Xeon E5-2690 - 96GB RAM - Software mdadm RAID10 (6 x SSDs) Postgres is used in a sort of DWH application, so all the resources are assigned to it and the aim is to maximize the single transaction performance instead of balancing between multiple connections. The configuration variables I changed are the following ones: checkpoint_completion_target = 0.9 data_directory = '/mnt/raid10/pg_data_9.6.2' default_statistics_target = 1000 effective_cache_size = 72GB effective_io_concurrency = 1000 listen_addresses = '127.0.0.1,192.168.2.90' maintenance_work_mem = 1GB max_connections=32 random_page_cost=1.2 seq_page_cost=1.0 shared_buffers = 24GB work_mem = 512MB The kernel configuration in /etc/sysctl.conf is: # 24GB = (24*1024*1024*1024) kernel.shmmax = 25769803776 # 6MB = (24GB/4096) dove 4096 e' uguale a "getconf PAGE_SIZE" kernel.shmall = 6291456 kernel.sched_migration_cost_ns = 5000000 kernel.sched_autogroup_enabled = 0 vm.overcommit_memory = 2 vm.overcommit_ratio = 90 vm.swappiness = 4 vm.zone_reclaim_mode = 0 vm.dirty_ratio = 15 vm.dirty_background_ratio = 3 vm.nr_hugepages = 12657 vm.min_free_kbytes=262144 dev.raid.speed_limit_max=1000000 dev.raid.speed_limit_min=1000000 Huge pages are being used on this machine and Postgres allocates 24GB immediately after starting up, as set by vm.nr_hugepages = 12657. My concern is that it never uses more than 24GB. For example, I’m running 16 queries that use a lot of CPU (they do time series expansion and some arithmetics). I estimate they will generate a maximum of 2.5 billions of rows. Those queries are running since 48 hours and don’t know when they will finish, but RAM never overpassed those 24GB (+ some system). Output from free -ht: total used free shared buff/cache available Mem: 94G 28G 46G 17M 19G 64G Swap: 15G 0B 15G Total: 109G 28G 61G Output from vmstat -S M: procs -----------memory---------- ---swap-- -----io---- -system-- ------cpu----- r b swpd free buff cache si so bi bo in cs us sy id wa st 17 0 0 47308 197 19684 0 0 4 12 3 8 96 0 3 0 0 Output from top -U postgres: top - 10:54:19 up 2 days, 1:37, 1 user, load average: 16.00, 16.00, 16.00 Tasks: 347 total, 17 running, 330 sleeping, 0 stopped, 0 zombie %Cpu(s):100.0 us, 0.0 sy, 0.0 ni, 0.0 id, 0.0 wa, 0.0 hi, 0.0 si, 0.0 st KiB Mem : 98847584 total, 48442364 free, 30046352 used, 20358872 buff/cache KiB Swap: 15825916 total, 15825916 free, 0 used. 67547664 avail Mem PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND 9686 postgres 20 0 24.918g 214236 12628 R 100.0 0.2 2872:38 postgres 9687 postgres 20 0 24.918g 214212 12600 R 100.0 0.2 2872:27 postgres 9688 postgres 20 0 25.391g 709936 12708 R 100.0 0.7 2872:40 postgres 9691 postgres 20 0 24.918g 214516 12900 R 100.0 0.2 2865:23 postgres 9697 postgres 20 0 24.918g 214284 12676 R 100.0 0.2 2866:05 postgres 9698 postgres 20 0 24.922g 218608 12904 R 100.0 0.2 2872:31 postgres 9699 postgres 20 0 24.918g 214512 12904 R 100.0 0.2 2865:32 postgres 9702 postgres 20 0 24.922g 218332 12628 R 100.0 0.2 2865:24 postgres 9704 postgres 20 0 24.918g 214512 12904 R 100.0 0.2 2872:50 postgres 9710 postgres 20 0 24.918g 212364 12904 R 100.0 0.2 2865:38 postgres 9681 postgres 20 0 24.918g 212300 12596 R 99.7 0.2 2865:18 postgres 9682 postgres 20 0 24.918g 212108 12656 R 99.7 0.2 2872:34 postgres 9684 postgres 20 0 24.918g 212612 12908 R 99.7 0.2 2872:24 postgres 9685 postgres 20 0 24.918g 214208 12600 R 99.7 0.2 2872:47 postgres 9709 postgres 20 0 24.918g 214284 12672 R 99.7 0.2 2866:03 postgres 9693 postgres 20 0 24.918g 214300 12688 R 99.3 0.2 2865:59 postgres 9063 postgres 20 0 24.722g 14812 12956 S 0.3 0.0 0:07.36 postgres 9068 postgres 20 0 24.722g 6380 4232 S 0.3 0.0 0:02.15 postgres 9065 postgres 20 0 24.727g 10368 3516 S 0.0 0.0 0:04.24 postgres 9066 postgres 20 0 24.722g 4100 2248 S 0.0 0.0 0:06.04 postgres 9067 postgres 20 0 24.722g 4100 2248 S 0.0 0.0 0:01.37 postgres 9069 postgres 20 0 161740 4596 2312 S 0.0 0.0 0:04.48 postgres What’s wrong with this? There isn’t something wrong in RAM usage? Thank you all Pietro |
