Cpu usage 100% on slave. s_lock problem.

Hello.

Exist 2 identical server DELL PowerEdge™ R720, CPU Dual Intel® Xeon®
E5-2620 Hexa-Core inkl, RAM 256Gb, RAID-10 8 x 600 GB SAS 6 Gb/s 15000 rpm.

$ cat /etc/fedora-release
Fedora release 19

$ postgres --version
postgres (PostgreSQL) 9.2.4

Data ~220Gb and Indexes ~140Gb

iowait ~0.2-0.5. Disk usage only write ~0-2 Mb/sec

On each installed pg_bouncer. Pool size 24.

On Master in peak load ~1200 request/sec, ~30 ms/request avg, 24 CPU ~95% -
this is no problem
$ perf top
21,14% [kernel] [k] isolate_freepages_block
12,27% [unknown] [.] 0x00007fc1bb303be0
5,93% postgres [.] hash_search_with_hash_value
4,85% libbz2.so.1.0.6 [.] 0x000000000000a6e0
2,70% postgres [.] PinBuffer
2,34% postgres [.] slot_deform_tuple
1,92% libbz2.so.1.0.6 [.] BZ2_compressBlock
1,85% postgres [.] LWLockAcquire
1,69% postgres [.] heap_page_prune_opt
1,48% postgres [.] _bt_checkkeys
1,40% [kernel] [k] page_fault
1,36% postgres [.] _bt_compare
1,23% postgres [.] heap_hot_search_buffer
1,19% [kernel] [k] get_pageblock_flags_group
1,18% postgres [.] AllocSetAlloc

On Slave max ~400-500 request/sec, ~200 and up 24 ms/request avg, 24 CPU
~95% - this is problem
$ perf top
30,10% postgres [.] s_lock
22,90% [unknown] [.] 0x0000000000729cfe
4,98% postgres [.] RecoveryInProgress.part.9
4,89% postgres [.] LWLockAcquire
4,57% postgres [.] hash_search_with_hash_value
3,50% postgres [.] PinBuffer
2,31% postgres [.] heap_page_prune_opt
2,27% postgres [.] LWLockRelease
1,18% postgres [.] heap_hot_search_buffer
1,03% postgres [.] AllocSetAlloc
...

Slave at a much lower load than the master hangs on the function s_lock.
What can be done about it?

On Slave ~300 request/sec, ~5-8 ms/request avg, cpu usage ~20% - normal
work by small load
$ perf top
10,74% postgres [.] hash_search_with_hash_value
4,94% postgres [.] PinBuffer
4,61% postgres [.] AllocSetAlloc
3,57% postgres [.] heap_page_prune_opt
3,24% postgres [.] LWLockAcquire
2,47% postgres [.] heap_hot_search_buffer
2,11% postgres [.] SearchCatCache
1,90% postgres [.] LWLockRelease
1,87% postgres [.] _bt_compare
1,68% postgres [.] FunctionCall2Coll
1,46% postgres [.] _bt_checkkeys
1,24% postgres [.] copyObject
1,15% postgres [.] RecoveryInProgress.part.9
1,05% postgres [.] slot_deform_tuple
...

Configuration Master postgres.conf
listen_addresses = '*'
max_connections = 100
shared_buffers = 200GB
work_mem = 20MB
maintenance_work_mem = 2GB
effective_io_concurrency = 4
wal_level = hot_standby
fsync = on
synchronous_commit = off
full_page_writes = on
wal_writer_delay = 200ms
checkpoint_segments = 100
checkpoint_timeout = 15min
checkpoint_completion_target = 0.9
archive_mode = on
archive_command = 'pbzip2 -f -c %p > /opt/pg/wals/wals/%f.bz2'
max_wal_senders = 3
random_page_cost = 0.5
cpu_tuple_cost = 0.02
cpu_index_tuple_cost = 0.01
cpu_operator_cost = 0.005
effective_cache_size = 40GB
default_statistics_target = 300
logging_collector = on
log_filename = 'postgresql-%Y-%m-%d_%H%M%S.log'
log_truncate_on_rotation = on
log_rotation_age = 1d
log_rotation_size = 0
log_min_duration_statement = 1000
log_checkpoints = on
log_line_prefix = '%t %p %c-%l %x %q(%u, %d, %r, %a) '
log_lock_waits = on
track_io_timing = on
track_activity_query_size = 4096
autovacuum = on
log_autovacuum_min_duration = 0
autovacuum_freeze_max_age = 1500000000
datestyle = 'iso, dmy'
timezone = 'Europe/Moscow'
lc_messages = 'en_US.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'
shared_preload_libraries = 'pg_stat_statements'
pg_stat_statements.max = 1000
pg_stat_statements.track = all
max_locks_per_transaction = 264

Configuration Slave postgres.conf
listen_addresses = '*'
max_connections = 100
shared_buffers = 200GB
work_mem = 20MB
maintenance_work_mem = 2GB
effective_io_concurrency = 4
wal_level = hot_standby
fsync = on
synchronous_commit = off
full_page_writes = on
wal_writer_delay = 200ms
commit_delay = 1000
commit_siblings = 2
checkpoint_segments = 100
checkpoint_timeout = 15min
checkpoint_completion_target = 0.9
archive_mode = on
archive_command = 'pbzip2 -f -c %p > /opt/pg/wals/wals/%f.bz2'
max_wal_senders = 4
hot_standby = on
max_standby_archive_delay = 30s
max_standby_streaming_delay = 30s
hot_standby_feedback = on
random_page_cost = 0.5
cpu_tuple_cost = 0.02
cpu_index_tuple_cost = 0.01
cpu_operator_cost = 0.005
effective_cache_size = 40GB
default_statistics_target = 300
logging_collector = on
log_filename = 'postgresql-%Y-%m-%d_%H%M%S.log'
log_truncate_on_rotation = on
log_rotation_age = 1d
log_rotation_size = 0
log_min_duration_statement = 1000
log_checkpoints = on
log_line_prefix = '%t %p %c-%l %x %q(%u, %d, %r, %a) '
log_lock_waits = on
track_functions = none
track_io_timing = on
track_activity_query_size = 4096
autovacuum = on
datestyle = 'iso, dmy'
timezone = 'Europe/Moscow'
lc_messages = 'en_US.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'
shared_preload_libraries = 'pg_stat_statements'
pg_stat_statements.max = 1000
pg_stat_statements.track = all
max_locks_per_transaction = 264

Thanks.