Re: [PERFORM] Cpu usage 100% on slave. s_lock problem.

Hi,

What confuses me is that pg_read_barrier() is just a compiler barrier on
x86[-64] in barrier.h. According to my knowledge it needs to be an
lfence or the full barrier?
The linked papers from Paul McKenney - which are a great read - seem to
agree?

On 2013-09-27 23:12:17 +0200, Andres Freund wrote:
> On 2013-09-27 23:28:37 +0300, Heikki Linnakangas wrote:
> > The function RecoveryInProgress() function does just one load, to read the
> > variable, and wouldn't even need a barrier by itself. The other load or
> > store that needs to be protected by the barrier happens in the caller,
> > before or after the function, and we can't say for sure if it's a load or a
> > store. So, let's use pg_memory_barrier().
>
> The caller uses a spinlock, so it's guaranteed to write out before the
> spinlock is released. A write barrier (the spinlock in the startup
> process) should always be paired by a read barrier.

s/caller/startup process/

Greetings,

Andres Freund

--
Andres Freund http://www.2ndQuadrant.com/
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