Postgres 4x Slower Than It Was
https://dba.stackexchange.com/questions/108454
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Our Postgres performance has gone down to 1/4 of what it was, and we can't figure out why.
We have two machines with identical hardware (let's call them A and B):
Intel(R) Xeon(R) CPU E5-4640 0 @ 2.40GHz (64 cores)
384 GB RAM
15k SAS, 16 disk RAID 10 array
Each machine has essentially identical Postgres clusters with about 100 GB databases, with the following settings:
version: PostgreSQL 9.4.4 on x86_64-unknown-linux-gnu, compiled by gcc (GCC) 4.4.7 20120313 (Red Hat 4.4.7-11), 64-bit
bytea_output: escape
checkpoint_completion_target: 0.7
checkpoint_segments: 256
checkpoint_timeout: 30min
client_encoding: UTF8
cpu_index_tuple_cost: 0.001
cpu_operator_cost: 0.0005
cpu_tuple_cost: 0.003
DateStyle: ISO, MDY
default_text_search_config: pg_catalog.english
dynamic_shared_memory_type: posix
effective_cache_size: 128GB
from_collapse_limit: 4
hot_standby: on
join_collapse_limit: 4
lc_messages: en_US.UTF-8
lc_monetary: en_US.UTF-8
lc_numeric: en_US.UTF-8
lc_time: en_US.UTF-8
listen_addresses: *
log_destination: stderr
log_directory: pg_log
log_filename: postgresql-%Y-%m-%d_%H%M%S.log
log_line_prefix: < %m >
log_rotation_age: 1d
log_rotation_size: 0
log_timezone: US/Eastern
log_truncate_on_rotation: on
logging_collector: on
maintenance_work_mem: 1GB
max_connections: 256
max_replication_slots: 3
max_stack_depth: 2MB
max_standby_streaming_delay: 350min
max_wal_senders: 5
shared_buffers: 24GB
temp_buffers: 8MB
TimeZone: US/Eastern
wal_buffers: 4MB
wal_keep_segments: 5000
wal_level: hot_standby
work_mem: 96MB
Linux settings:
CentOS 6.6
/sys/kernel/mm/redhat_transparent_hugepage/enabled: Always
/sys/kernel/mm/redhat_transparent_hugepage/enabled: Always
/sys/kernel/mm/redhat_transparent_hugepage/defrag: Always
/proc/sys/vm/dirty_background_ratio: 10
/sys/block/sda/queue/scheduler: cfq
/sys/block/sda/queue/read_ahead_kb: 128
blockdev --report:
RO RA SSZ BSZ StartSec Size Device
rw 256 512 4096 0 2395518009344 /dev/sda
rw 256 512 4096 2048 1048576000 /dev/sda1
rw 256 512 4096 2050048 1792509214720 /dev/sda2
rw 256 512 4096 3503044608 314572800000 /dev/sda3
rw 256 512 4096 4117444608 149946368000 /dev/sda4
rw 256 512 4096 4410308608 137438953472 /dev/sda5
I don't claim to understand all that.
We have streaming replication that keeps a hot copy of A on B. That puts B under heavier load, especially in the memory department, and it goes into swap (so clearly we're doing something wrong, since we have 384 GB of RAM).
free -g (on A):
total used free shared buffers cached
Mem: 378 347 30 24 2 301
-/+ buffers/cache: 44 334
Swap: 127 1 126
free -g (on B):
total used free shared buffers cached
Mem: 378 366 11 49 2 340
-/+ buffers/cache: 23 354
Swap: 127 1 126
The load is usually 5 or 10, but at times will go to 30 - 60 for a few hours when intensive reporting or database operations are done.
Backing up the entire database used to take ~1 hour, now it takes ~4.
Syncing the database on A to B (B is used for development and we refresh the live data to from A to B) used to take ~1 hour, now it takes ~4.
Queries that used to take 30 seconds (for years) started hanging for days without returning (increasing the work_mem for that query solved that problem: Postgres 9.4.4 query takes forever).
We have Tomcat websites and processes that run, using C3P0 for pooling, and Apache / PHP sites and processes that run, using pgBouncer for pooling. We've considered having Tomcat use pgBouncer as well.
We've considered trying to lower our max connections from 256 to 64 (256 is from before we were using connection pooling).
Our current settings come from a combination of pgtune and research, but my confidence in our current configuration isn't high, and our the performance drop doesn't help that confidence.
Any recommendations? Any additional info needed?
Update
Output of iostat:
Server A
Linux 2.6.32-504.23.4.el6.x86_64 (openlink1.radyn.com) 08/05/2015 _x86_64_ (64 CPU)
avg-cpu: %user %nice %system %iowait %steal %idle
27.09 0.03 1.15 0.06 0.00 71.67
Device: tps Blk_read/s Blk_wrtn/s Blk_read Blk_wrtn
sda 258.93 2136.65 20871.52 4370455736 42692153072
Server B
Linux 2.6.32-504.23.4.el6.x86_64 (openlink2.radyn.com) 08/05/2015 _x86_64_ (64 CPU)
avg-cpu: %user %nice %system %iowait %steal %idle
26.90 0.00 1.58 0.17 0.00 71.35
Device: tps Blk_read/s Blk_wrtn/s Blk_read Blk_wrtn
sda 459.18 12641.47 17765.60 28973539688 40717751832
Output of vmstat:
Server A
procs -----------memory---------- ---swap-- -----io---- --system-- -----cpu-----
r b swpd free buff cache si so bi bo in cs us sy id wa st
7 0 1297844 8265380 2688960 333189664 0 0 17 163 0 0 27 1 72 0 0
Server B
procs -----------memory---------- ---swap-- -----io---- --system-- -----cpu-----
r b swpd free buff cache si so bi bo in cs us sy id wa st
9 0 3321548 16228276 2221908 349418368 0 0 99 139 0 0 27 2 71 0 0
Output of sar:
Server A
Linux 2.6.32-504.23.4.el6.x86_64 (openlink1.radyn.com) 08/05/2015 _x86_64_ (64 CPU)
12:00:01 AM CPU %user %nice %system %iowait %steal %idle
12:10:01 AM all 13.25 0.00 1.05 0.04 0.00 85.66
12:20:01 AM all 11.98 0.00 0.53 0.03 0.00 87.46
12:30:01 AM all 11.86 0.00 0.67 0.03 0.00 87.43
12:40:01 AM all 12.33 0.00 0.94 0.04 0.00 86.68
12:50:01 AM all 11.39 0.00 0.52 0.06 0.00 88.03
01:00:01 AM all 13.58 0.00 1.28 0.03 0.00 85.11
01:10:01 AM all 13.37 0.00 0.82 0.02 0.00 85.79
01:20:01 AM all 11.74 0.00 0.54 0.01 0.00 87.70
01:30:01 AM all 12.00 0.00 0.70 0.02 0.00 87.28
01:40:01 AM all 13.10 0.00 0.80 0.02 0.00 86.08
01:50:01 AM all 13.19 0.00 1.06 0.02 0.00 85.73
02:00:02 AM all 15.62 0.00 1.55 0.03 0.00 82.80
02:10:01 AM all 18.72 0.00 2.98 0.03 0.00 78.27
02:20:02 AM all 15.95 0.12 2.33 0.05 0.00 81.55
02:30:01 AM all 13.58 0.01 0.89 0.01 0.00 85.51
02:40:01 AM all 19.23 0.00 1.91 0.05 0.00 78.80
02:50:02 AM all 23.95 0.00 0.92 0.05 0.00 75.08
03:00:01 AM all 13.69 0.00 0.59 0.01 0.00 85.72
03:10:01 AM all 12.87 0.00 0.49 0.01 0.00 86.64
03:20:01 AM all 12.18 0.00 0.69 0.02 0.00 87.11
03:30:01 AM all 11.82 0.74 0.70 0.05 0.00 86.69
03:40:01 AM all 62.02 0.00 2.18 0.01 0.00 35.79
03:50:01 AM all 72.96 0.00 0.71 0.00 0.00 26.32
04:00:01 AM all 71.97 0.00 0.72 0.00 0.00 27.30
04:10:01 AM all 71.71 0.00 0.71 0.00 0.00 27.57
04:20:01 AM all 72.40 0.00 0.80 0.01 0.00 26.80
04:30:01 AM all 68.69 0.00 1.24 0.00 0.00 30.07
04:40:01 AM all 68.68 0.00 1.12 0.02 0.00 30.18
04:50:01 AM all 72.59 0.00 0.79 0.00 0.00 26.62
05:00:01 AM all 72.09 0.00 0.81 0.00 0.00 27.10
05:10:01 AM all 72.61 0.00 0.79 0.00 0.00 26.59
05:20:01 AM all 72.19 0.00 0.83 0.00 0.00 26.98
05:30:01 AM all 75.98 0.00 1.14 0.00 0.00 22.87
05:40:02 AM all 73.85 0.00 1.19 0.00 0.00 24.96
05:50:02 AM all 73.47 0.00 1.21 0.00 0.00 25.32
06:00:01 AM all 75.27 0.00 1.24 0.00 0.00 23.49
06:10:01 AM all 76.56 0.00 1.18 0.00 0.00 22.25
06:20:01 AM all 77.06 0.20 1.24 0.00 0.00 21.50
06:30:01 AM all 76.44 0.00 1.29 0.00 0.00 22.27
06:40:01 AM all 77.16 0.00 1.44 0.00 0.00 21.39
06:50:01 AM all 76.88 0.00 1.18 0.00 0.00 21.94
07:00:01 AM all 76.28 0.00 1.12 0.00 0.00 22.60
07:10:01 AM all 49.72 0.00 1.49 0.11 0.00 48.67
07:20:01 AM all 12.78 0.00 1.01 0.00 0.00 86.21
07:30:01 AM all 14.26 0.00 1.04 0.00 0.00 84.70
07:40:01 AM all 15.19 0.00 1.11 0.00 0.00 83.70
07:50:01 AM all 12.85 0.00 0.98 0.00 0.00 86.17
08:00:01 AM all 14.24 0.00 0.94 0.00 0.00 84.82
08:10:01 AM all 13.09 0.00 0.98 0.00 0.00 85.93
08:20:01 AM all 13.16 0.00 0.88 0.00 0.00 85.96
08:30:01 AM all 9.87 0.00 0.53 0.00 0.00 89.60
08:40:01 AM all 8.41 0.00 0.66 0.00 0.00 90.92
08:50:01 AM all 10.09 0.00 0.75 0.00 0.00 89.16
09:00:01 AM all 7.66 0.00 0.52 0.00 0.00 91.82
09:10:01 AM all 6.68 0.00 0.43 0.00 0.00 92.89
09:10:01 AM CPU %user %nice %system %iowait %steal %idle
09:20:01 AM all 7.20 0.00 0.41 0.00 0.00 92.39
09:30:01 AM all 6.74 0.00 0.44 0.00 0.00 92.82
09:40:01 AM all 6.70 0.00 0.43 0.00 0.00 92.87
09:50:01 AM all 8.12 0.00 0.54 0.04 0.00 91.30
10:00:01 AM all 10.44 0.00 0.60 0.02 0.00 88.93
10:10:01 AM all 10.86 0.00 0.60 0.01 0.00 88.53
10:20:01 AM all 14.46 0.00 0.77 0.06 0.00 84.72
10:30:01 AM all 9.31 0.13 0.84 0.10 0.00 89.63
10:40:02 AM all 10.45 0.00 0.81 0.11 0.00 88.63
Average: all 32.89 0.02 0.96 0.02 0.00 66.11
Server B
Linux 2.6.32-504.23.4.el6.x86_64 (openlink2.radyn.com) 08/05/2015 _x86_64_ (64 CPU)
12:00:01 AM CPU %user %nice %system %iowait %steal %idle
12:10:01 AM all 12.29 0.00 2.65 0.30 0.00 84.76
12:20:01 AM all 16.31 0.00 1.38 0.15 0.00 82.16
12:30:01 AM all 13.46 0.00 1.59 0.07 0.00 84.88
12:40:01 AM all 13.05 0.00 1.16 0.17 0.00 85.61
12:50:01 AM all 11.72 0.00 1.39 0.11 0.00 86.79
01:00:01 AM all 11.96 0.00 1.77 0.06 0.00 86.21
01:10:01 AM all 13.21 0.00 1.69 0.06 0.00 85.04
01:20:01 AM all 13.19 0.00 2.14 0.05 0.00 84.62
01:30:03 AM all 19.11 0.00 4.31 0.06 0.00 76.52
01:40:02 AM all 9.29 0.00 4.75 0.04 0.00 85.91
01:50:02 AM all 7.16 0.00 4.81 0.04 0.00 87.99
02:00:03 AM all 6.56 0.00 5.26 0.06 0.00 88.12
02:10:02 AM all 8.05 0.00 7.09 0.06 0.00 84.80
02:20:03 AM all 8.54 0.00 7.75 0.08 0.00 83.62
02:30:03 AM all 2.99 0.00 6.20 0.09 0.00 90.72
02:40:03 AM all 10.79 0.00 7.79 0.21 0.00 81.21
02:50:03 AM all 5.88 0.00 4.97 0.16 0.00 88.99
03:00:02 AM all 14.17 0.00 4.99 0.47 0.00 80.37
03:10:01 AM all 17.17 0.00 4.18 0.26 0.00 78.40
03:20:01 AM all 29.50 0.00 3.36 0.11 0.00 67.03
03:30:01 AM all 25.16 0.00 3.05 0.15 0.00 71.64
03:40:01 AM all 19.70 0.00 2.29 0.15 0.00 77.86
03:50:01 AM all 28.69 0.00 3.01 0.09 0.00 68.21
04:00:01 AM all 17.61 0.00 2.73 0.08 0.00 79.58
04:10:01 AM all 16.72 0.00 2.95 0.09 0.00 80.25
04:20:01 AM all 13.50 0.00 2.47 0.05 0.00 83.98
04:30:03 AM all 14.88 0.00 5.20 0.08 0.00 79.84
04:40:02 AM all 12.05 0.01 6.05 0.10 0.00 81.79
04:50:01 AM all 9.92 0.00 6.89 0.03 0.00 83.16
05:00:03 AM all 5.89 0.00 6.89 0.02 0.00 87.20
05:10:02 AM all 5.22 0.00 5.55 0.05 0.00 89.18
05:20:02 AM all 6.02 0.00 5.01 0.04 0.00 88.94
05:30:03 AM all 8.11 0.00 6.05 0.02 0.00 85.82
05:40:02 AM all 13.53 0.00 3.94 0.01 0.00 82.52
05:50:01 AM all 18.90 0.00 2.48 0.02 0.00 78.60
06:00:01 AM all 19.09 0.00 1.64 0.01 0.00 79.26
06:10:01 AM all 18.63 0.00 1.84 0.06 0.00 79.47
06:20:01 AM all 19.13 0.00 1.72 0.05 0.00 79.11
06:30:01 AM all 17.73 0.00 1.94 0.02 0.00 80.31
06:40:01 AM all 17.97 0.00 1.58 0.02 0.00 80.42
06:50:02 AM all 12.25 0.00 2.00 0.02 0.00 85.72
07:00:01 AM all 10.04 0.00 1.31 0.00 0.00 88.64
07:10:01 AM all 13.39 0.00 1.59 0.00 0.00 85.02
07:20:01 AM all 14.84 0.00 1.49 0.00 0.00 83.67
07:30:01 AM all 12.36 0.00 0.80 0.01 0.00 86.84
07:40:01 AM all 12.07 0.00 0.71 0.01 0.00 87.21
07:50:01 AM all 12.98 0.00 1.14 0.00 0.00 85.88
08:00:01 AM all 12.62 0.00 0.93 0.00 0.00 86.44
08:10:01 AM all 11.77 0.00 0.87 0.00 0.00 87.36
08:20:01 AM all 11.79 0.00 1.61 0.00 0.00 86.60
08:30:01 AM all 10.80 0.00 0.79 0.00 0.00 88.40
08:40:02 AM all 13.49 0.00 1.78 0.00 0.00 84.72
08:50:01 AM all 12.46 0.00 1.39 0.00 0.00 86.15
09:00:02 AM all 12.28 0.00 0.83 0.00 0.00 86.89
09:10:01 AM all 12.65 0.00 0.77 0.01 0.00 86.57
09:10:01 AM CPU %user %nice %system %iowait %steal %idle
09:20:01 AM all 12.44 0.00 0.78 0.00 0.00 86.78
09:30:01 AM all 12.96 0.00 1.01 0.00 0.00 86.03
09:40:01 AM all 11.71 0.00 0.80 0.00 0.00 87.49
09:50:01 AM all 15.23 0.00 2.04 0.06 0.00 82.67
10:00:01 AM all 14.60 0.00 1.66 0.02 0.00 83.72
10:10:01 AM all 13.97 0.00 2.76 0.01 0.00 83.26
10:20:01 AM all 15.34 0.00 1.51 0.01 0.00 83.14
10:30:01 AM all 12.84 0.00 1.34 0.80 0.00 85.03
10:40:01 AM all 12.96 0.00 1.43 0.81 0.00 84.80
10:50:01 AM all 14.48 0.00 1.47 0.85 0.00 83.20
Average: all 13.46 0.00 2.85 0.10 0.00 83.59
Solution
Based on your configurations and output, the only suggestions I can make for you to try are the following.
Disable Transparent Huge Pages. Evidence from the PostgreSQL mailing lists, and Red Hat themselves recommend disabling THP for database workloads here
Set
vm.zone_reclaim_mode=0. Discussion hereSet your elevator to deadline from cfq. Red Hat recommends deadline for enterprise storage, which it sounds like you have. Discussion here
Change from setting
vm.dirty_background_ratiotovm.dirty_background_bytesandvm.dirty_bytes.The defaults are 10% which given your 384GB of RAM is 38.4 GB of RAM that needs to be dirty before the kernel starts writing it out in the background. I would set the values to 64MB and 50% of the controller RAM, respectively, though that's based on my own anecdotal experience.
Hopefully some of these suggestions work out for you.
