Re: Spinlocks, yet again: analysis and proposed patches

"Tom Lane" <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote
>
> Not really --- that patch was intended to ensure that LWLocks don't
> unnecessarily cross two cache lines. It doesn't ensure that two
> different LWLocks aren't sharing a cache line. You could do that
> by increasing LWLOCK_PADDED_SIZE to the cache line size for your
> hardware, if you know what that is.
>
Exactly, this is one way -- if we make LWLOCK_PADDED_SIZE big enough, we can
assure that one lwlock one cacheline. If so, maybe we should plug in a check
like LMBench in ./configure to guess out current cacheline size. But this
way looks like overkill -- a compromise is to pad only some of the LWLocks
big enough but not all (for example, the buffer content lock array).

Regards,
Qingqing