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