Re: Protect syscache from bloating with negative cache entries

Hi,

On 19/11/2020 07:25, Kyotaro Horiguchi wrote:
> Performance measurement on the attached showed better result about
> searching but maybe worse for cache entry creation.  Each time number
> is the mean of 10 runs.
> 
> # Cacache (negative) entry creation
>             :  time(ms) (% to master)
> master     :  3965.61    (100.0)
> patched-off:  4040.93    (101.9)
> patched-on :  4032.22    (101.7)
> 
> # Searching negative cache entries
> master     :  8173.46    (100.0)
> patched-off:  7983.43    ( 97.7)
> patched-on :  8049.88    ( 98.5)
> 
> # Creation, searching and expiration
> master     :  6393.23    (100.0)
> patched-off:  6527.94    (102.1)
> patched-on : 15880.01    (248.4)
> 
> 
> That is, catcache searching gets faster by 2-3% but creation gets
> slower by about 2%. If I moved the condition of 2 further up to
> CatalogCacheCreateEntry(), that degradation reduced to 0.6%.
> 
> # Cacache (negative) entry creation
> master      :  3967.45   (100.0)
> patched-off :  3990.43   (100.6)
> patched-on  :  4108.96   (103.6)
> 
> # Searching negative cache entries
> master      :  8106.53   (100.0)
> patched-off :  8036.61   ( 99.1)
> patched-on  :  8058.18   ( 99.4)
> 
> # Creation, searching and expiration
> master      :  6395.00   (100.0)
> patched-off :  6416.57   (100.3)
> patched-on  : 15830.91   (247.6)

Can you share the exact script or steps to reproduce these numbers? I 
presume these are from the catcachebench extension, but I can't figure 
out which scenario above corresponds to which catcachebench test. Also, 
catcachebench seems to depend on a bunch of tables being created in 
schema called "test"; what tables did you use for the above numbers?

- Heikki