Too long startup time after crash.

Hi.

After the upgrade postgresql had a strange behavior. After the crash, server launch was take a long time, up to 30-40 minutes sometimes. When connecting to the server (as well as in the log), the message - "the database system is starting up". Startup process consumes 0.4 - 1% CPU.

Tried different version 9.5.[2,3,4], 9.6.1 (9.4 works fine). On the Internet this problem is not met, perhaps the problem lies in a combination of different factors (configuration database, the Linux kernel), may be my config is wrong?

Technical details:

Gentoo Linux 4.4.2-hardened
current pg version 9.6.1
## pg config:

listen_addresses = '*'
port = 5432
max_connections = 500
shared_buffers = 2048MB
temp_buffers = 16MB
work_mem = 64MB
maintenance_work_mem = 512MB
max_stack_depth = 4MB
dynamic_shared_memory_type = posix
wal_level = replica
wal_buffers = 8MB
checkpoint_completion_target = 0.85
archive_mode = on
archive_command = 'gzip < %p > /home/pgbasebackup/xlogs/%f.gz'
max_wal_senders = 3
effective_cache_size = 9GB
log_min_duration_statement = 1500
log_timezone = 'Asia/Yekaterinburg'
datestyle = 'iso, dmy'
timezone = 'Asia/Yekaterinburg'
lc_messages = 'ru_RU.UTF-8'
lc_monetary = 'ru_RU.UTF-8'
lc_numeric = 'ru_RU.UTF-8'
lc_time = 'ru_RU.UTF-8'
default_text_search_config = 'pg_catalog.russian'
plperl.on_init = 'use utf8; use re; package utf8; require "utf8_heavy.pl";'

## end of config

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Thanks,

Vitaliy