Re: Clock sweep not caching enough B-Tree leaf pages?

On 2014-04-16 07:55:44 -0500, Merlin Moncure wrote:
> > 1. Bgwriter needs to be improved so that it can help in reducing
> >     usage count and finding next victim buffer (run the clock sweep
> >     and add buffers to the free list).
> > 2. SetLatch for bgwriter (wakeup bgwriter) when elements in freelist
> >     are less.
> > 3. Split the workdone globallock (Buffreelist) in StrategyGetBuffer
> >     (a spinlock for the freelist, and an lwlock for the clock sweep).
> >     Here we can try to make it lock free based on atomic ops as
> >     well.
> > 4. Bgwriter needs to be more aggressive, logic based on which it
> >     calculates how many buffers it needs to process needs to be
> >     improved.
> > 5. Contention around buffer mapping locks.
> > 6. Cacheline bouncing around the buffer header spinlocks, is there
> >     anything we can do to reduce this?
> > 7. Choose Optimistically used buffer in StrategyGetBuffer().
> > 8. Don't bump the usage count every time buffer is pinned.
> 
> What about:  9. Don't wait on locked buffer in the clock sweep.

I don't think we do that? Or are you referring to locked buffer headers?

Greetings,

Andres Freund

-- Andres Freund                       http://www.2ndQuadrant.com/PostgreSQL Development, 24x7 Support, Training &
Services