Thread: Small catcache optimization

Hi,

Heikki's catcache rehashing stuff reminded me that I'd posted an
optimization to catcache (20121220153555.GH4303@awork2.anarazel.de) some
time back which I didn't have energy to pursue at that point.

I've brushed the patch up a bit and verified it still gives be a
performance improvement. It's still about 2% in a readonly pgbench on my
elderly laptop.

There's basically two tricks in the patch:
1) Don't always copy the cache's ScanKey to the stack. Instead pass
   an array of arguments around. That get's rid of a good amount of
   memcpy()ing in the common, cached case.
2) If we have to memcpy() because we need to pass a ScanKey to
   systable_*, copy only cache->cc_nkey * sizeof(ScanKeyData) instead of
   always copying the maximum size.

I'd be nicer to get rid of the mostly copied HeapKeyTestArg, but I don't
immediately see how.

Greetings,

Andres Freund

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

On Thu, Sep  5, 2013 at 09:13:23PM +0200, Andres Freund wrote:
> Hi,
> 
> Heikki's catcache rehashing stuff reminded me that I'd posted an
> optimization to catcache (20121220153555.GH4303@awork2.anarazel.de) some
> time back which I didn't have energy to pursue at that point.
> 
> I've brushed the patch up a bit and verified it still gives be a
> performance improvement. It's still about 2% in a readonly pgbench on my
> elderly laptop.
> 
> There's basically two tricks in the patch:
> 1) Don't always copy the cache's ScanKey to the stack. Instead pass
>    an array of arguments around. That get's rid of a good amount of
>    memcpy()ing in the common, cached case.
> 2) If we have to memcpy() because we need to pass a ScanKey to
>    systable_*, copy only cache->cc_nkey * sizeof(ScanKeyData) instead of
>    always copying the maximum size.
> 
> I'd be nicer to get rid of the mostly copied HeapKeyTestArg, but I don't
> immediately see how.

Where are we on this?

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http://enterprisedb.com
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