Re: [HACKERS] lock mode for ControlFileLock which pg_start_backup uses

2010-03-09 Thread Takahiro Itagaki 

Fujii Masao  wrote:

> Currently pg_start_backup() accesses the shared ControlFile
> by using ControlFileLock with LW_EXCLUSIVE lock mode. But
> since that access is read-only operation, LW_SHARED should
> be chosen instead of LW_EXCLUSIVE.
> 
> The attached patch changes the lock mode which pg_start_backup()
> uses. Is it worth applying this patch?

Thanks, applied.

Regards,
---
Takahiro Itagaki
NTT Open Source Software Center



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Re: [HACKERS] lock mode for ControlFileLock which pg_start_backup uses

2010-03-09 Thread Heikki Linnakangas 
Takahiro Itagaki wrote:
> Fujii Masao  wrote:
>> The attached patch changes the lock mode which pg_start_backup()
>> uses. Is it worth applying this patch?
> 
> I think the patch is reasonable to represent what we are doing,
> even if there is no performance benefits from it.

Agreed.

-- 
  Heikki Linnakangas
  EnterpriseDB   http://www.enterprisedb.com

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Re: [HACKERS] lock mode for ControlFileLock which pg_start_backup uses

2010-03-08 Thread Takahiro Itagaki 

Fujii Masao  wrote:

> Currently pg_start_backup() accesses the shared ControlFile
> by using ControlFileLock with LW_EXCLUSIVE lock mode. But
> since that access is read-only operation, LW_SHARED should
> be chosen instead of LW_EXCLUSIVE.

Almost all operations of ControlFileLock is in LW_EXCLUSIVE, but
there is one usage of LWLockConditionalAcquire(ControlFileLock, LW_SHARED)
in XLogNeedsFlush().

> The attached patch changes the lock mode which pg_start_backup()
> uses. Is it worth applying this patch?

I think the patch is reasonable to represent what we are doing,
even if there is no performance benefits from it.

Regards,
---
Takahiro Itagaki
NTT Open Source Software Center



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