linux-kernel - Re: [PATCH v3 0/6] powerpc: queued spinlocks and rwlocks

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Message-ID: <20200708084106.GE597537@hirez.programming.kicks-ass.net>
Date:   Wed, 8 Jul 2020 10:41:06 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Nicholas Piggin <npiggin@...il.com>
Cc:     linuxppc-dev@...ts.ozlabs.org, Waiman Long <longman@...hat.com>,
        Anton Blanchard <anton@...abs.org>,
        Boqun Feng <boqun.feng@...il.com>, kvm-ppc@...r.kernel.org,
        linux-arch@...r.kernel.org, linux-kernel@...r.kernel.org,
        Ingo Molnar <mingo@...hat.com>,
        virtualization@...ts.linux-foundation.org,
        Will Deacon <will@...nel.org>
Subject: Re: [PATCH v3 0/6] powerpc: queued spinlocks and rwlocks

On Tue, Jul 07, 2020 at 03:57:06PM +1000, Nicholas Piggin wrote:
> Yes, powerpc could certainly get more performance out of the slow
> paths, and then there are a few parameters to tune.

Can you clarify? The slow path is already in use on ARM64 which is weak,
so I doubt there's superfluous serialization present. And Will spend a
fair amount of time on making that thing guarantee forward progressm, so
there just isn't too much room to play.

> We don't have a good alternate patching for function calls yet, but
> that would be something to do for native vs pv.

Going by your jump_label implementation, support for static_call should
be fairly straight forward too, no?

  https://lkml.kernel.org/r/20200624153024.794671356@infradead.org