tree d7bbface71207011bb2b757d7329c4e89a4a4d78
parent fff96b441f73195f1407c38ba2ad7d904a6458f4
author Willy Tarreau <w@1wt.eu> 1618612298 +0200
committer Willy Tarreau <w@1wt.eu> 1618838673 +0200
encoding latin1

MEDIUM: pools: move the cache into the pool header

Initially per-thread pool caches were stored into a fixed-size array.
But this was a bit ugly because the last allocated pools were not able
to benefit from the cache at all. As a work around to preserve
performance, a size of 64 cacheable pools was set by default (there
are 51 pools at the moment, excluding any addon and debugging code),
so all in-tree pools were covered, at the expense of higher memory
usage.

In addition an index had to be calculated for each pool, and was used
to acces the pool cache head into that array. The pool index was not
even stored into the pools so it was required to determine it to access
the cache when the pool was already known.

This patch changes this by moving the pool cache head into the pool
head itself. This way it is certain that each pool will have its own
cache. This removes the need for index calculation.

The pool cache head is 32 bytes long so it was aligned to 64B to avoid
false sharing between threads. The extra cost is not huge (~2kB more
per pool than before), and we'll make better use of that space soon.
The pool cache head contains the size, which should probably be removed
since it's already in the pool's head.