Skip site navigation (1) Skip section navigation (2)

Re: sinval synchronization considered harmful

From: Robert Haas <robertmhaas(at)gmail(dot)com>
To: Noah Misch <noah(at)2ndquadrant(dot)com>
Cc: pgsql-hackers(at)postgresql(dot)org
Subject: Re: sinval synchronization considered harmful
Date: 2011-07-22 00:25:08
Message-ID: (view raw, whole thread or download thread mbox)
Lists: pgsql-hackers
On Thu, Jul 21, 2011 at 6:43 PM, Noah Misch <noah(at)2ndquadrant(dot)com> wrote:
> On Wed, Jul 20, 2011 at 09:46:33PM -0400, Robert Haas wrote:
>> Profiling this combination of patches reveals that there is still some
>> pretty ugly spinlock contention on sinval's msgNumLock.  And it occurs
>> to me that on x86, we really don't need this lock ... or
>> SInvalReadLock ... or a per-backend mutex.  The whole of
>> SIGetDataEntries() can pretty easily be made lock-free.  The only real
>> changes that seem to be are needed are (1) to use a 64-bit counter, so
>> you never need to decrement
> On second thought, won't this be inadequate on 32-bit systems, where updating
> the 64-bit counter produces two stores?  You must avoid reading it between those
> stores.

Now that is a potentially big problem.

Robert Haas
The Enterprise PostgreSQL Company

In response to


pgsql-hackers by date

Next:From: Josh KupershmidtDate: 2011-07-22 01:17:28
Subject: Re: psql: bogus descriptions displayed by \d+
Previous:From: Robert HaasDate: 2011-07-22 00:24:51
Subject: Re: sinval synchronization considered harmful

Privacy Policy | About PostgreSQL
Copyright © 1996-2017 The PostgreSQL Global Development Group