Re: User concurrency thresholding: where do I look?

With CLOG 16 the drp[s comes at about 1150 users with the following lock
stats
bash-3.00# ./4_lwlock_waits.d 16404

Lock Id Mode Count
ProcArrayLock Shared 2
XidGenLock Exclusive 2
XidGenLock Shared 4
WALInsertLock Exclusive 7
CLogControlLock Shared 8
WALWriteLock Exclusive 46
ProcArrayLock Exclusive 64
CLogControlLock Exclusive 263

Lock Id Mode Combined Time (ns)
XidGenLock Exclusive 528300
ProcArrayLock Shared 968800
WALInsertLock Exclusive 4090900
XidGenLock Shared 73987600
WALWriteLock Exclusive 86200700
ProcArrayLock Exclusive 130756000
CLogControlLock Shared 240471000
CLogControlLock Exclusive 4115158500

So I think 32 is a better option for CLogs before ProcArrayLock becomes
the bottleneck.

Though I havent seen what we can do with ProcArrayLock problem.

Regards,
Jignesh

Jignesh K. Shah wrote:
> Using CLOG Buffers 32 and the commit sibling check patch I still see a
> drop at 1200-1300 users..
>
>
>
> bash-3.00# ./4_lwlock_waits.d 18250
>
> Lock Id Mode Count
> XidGenLock Shared 1
> CLogControlLock Shared 2
> ProcArrayLock Shared 2
> XidGenLock Exclusive 4
> CLogControlLock Exclusive 15
> WALInsertLock Exclusive 18
> WALWriteLock Exclusive 38
> ProcArrayLock Exclusive 77
>
> Lock Id Mode Combined Time (ns)
> XidGenLock Shared 88700
> WALInsertLock Exclusive 69556000
> ProcArrayLock Shared 95656800
> XidGenLock Exclusive 139634100
> CLogControlLock Exclusive 148822200
> CLogControlLock Shared 161630000
> WALWriteLock Exclusive 332781800
> ProcArrayLock Exclusive 5688265500
>
> bash-3.00# ./4_lwlock_waits.d 18599
>
> Lock Id Mode Count
> ProcArrayLock Shared 2
> XidGenLock Exclusive 3
> XidGenLock Shared 4
> CLogControlLock Shared 5
> WALInsertLock Exclusive 10
> CLogControlLock Exclusive 21
> WALWriteLock Exclusive 28
> ProcArrayLock Exclusive 54
>
> Lock Id Mode Combined Time (ns)
> XidGenLock Exclusive 5688800
> WALInsertLock Exclusive 11424700
> CLogControlLock Shared 55589100
> ProcArrayLock Shared 135220400
> WALWriteLock Exclusive 177906900
> XidGenLock Shared 524146500
> CLogControlLock Exclusive 524563900
> ProcArrayLock Exclusive 5828744500
>
> bash-3.00#
> bash-3.00# ./6_lwlock_stack.d 4 18599
>
> Lock Id Mode Count
> ProcArrayLock Shared 1
> ProcArrayLock Exclusive 52
>
> Lock Id Mode Combined Time (ns)
> ProcArrayLock Shared 41428300
> ProcArrayLock Exclusive 3858386500
>
> Lock Id Combined Time (ns)
>
>
> postgres`LWLockAcquire+0x1f0
> postgres`GetSnapshotData+0x120
> postgres`GetTransactionSnapshot+0x80
> postgres`PortalStart+0x198
> postgres`exec_bind_message+0x84c
> postgres`PostgresMain+0x17f8
> postgres`BackendRun+0x2f8
> postgres`ServerLoop+0x680
> postgres`PostmasterMain+0xda8
> postgres`main+0x3d0
> postgres`_start+0x17c
> Shared 41428300
>
> postgres`LWLockAcquire+0x1f0
> postgres`CommitTransaction+0x104
> postgres`CommitTransactionCommand+0xbc
> postgres`finish_xact_command+0x78
> postgres`exec_execute_message+0x42c
> postgres`PostgresMain+0x1838
> postgres`BackendRun+0x2f8
> postgres`ServerLoop+0x680
> postgres`PostmasterMain+0xda8
> postgres`main+0x3d0
> postgres`_start+0x17c
> Exclusive 3858386500
>
>
> -Jignesh
>
>
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