Re: LWLock optimization for multicore Power machines

From: Andres Freund <andres(at)anarazel(dot)de>
To: Alexander Korotkov <a(dot)korotkov(at)postgrespro(dot)ru>
Cc: pgsql-hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: LWLock optimization for multicore Power machines
Date: 2017-02-06 19:53:44
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On 2017-02-03 20:01:03 +0300, Alexander Korotkov wrote:
> Using assembly in lwlock.c looks rough. This is why I refactored it by
> introducing new atomic operation pg_atomic_fetch_mask_add_u32 (see
> lwlock-power-2.patch). It checks that all masked bits are clear and then
> adds to variable. This atomic have special assembly implementation for
> Power, and generic implementation for other platforms with loop of CAS.
> Probably we would have other implementations for other architectures in
> future. This level of abstraction is the best I managed to invent.

I think that's a reasonable approach. And I think it might be worth
experimenting with a more efficient implementation on x86 too, using
hardware lock elision / HLE and/or tsx.


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