From: Peter Zijlstra <peterz@infradead.org>
To: Mel Gorman <mgorman@techsingularity.net>
Cc: Will Deacon <will@kernel.org>,
Davidlohr Bueso <dave@stgolabs.net>,
linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org
Subject: Re: Loadavg accounting error on arm64
Date: Mon, 16 Nov 2020 13:46:57 +0100 [thread overview]
Message-ID: <20201116124657.GA3121392@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <20201116091054.GL3371@techsingularity.net>
On Mon, Nov 16, 2020 at 09:10:54AM +0000, Mel Gorman wrote:
> Similarly, it's not clear why the arm64 implementation
> does not call smp_acquire__after_ctrl_dep in the smp_load_acquire
> implementation. Even when it was introduced, the arm64 implementation
> differed significantly from the arm implementation in terms of what
> barriers it used for non-obvious reasons.
This is because ARM64's smp_cond_load_acquire() implementation uses
smp_load_aquire() directly, as opposed to the generic version that uses
READ_ONCE().
This is because ARM64 has a load-acquire instruction, which is highly
optimized, and generally considered cheaper than the smp_rmb() from
smp_acquire__after_ctrl_dep().
Or so I've been led to believe.
next prev parent reply other threads:[~2020-11-16 12:47 UTC|newest]
Thread overview: 36+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-11-16 9:10 Mel Gorman
2020-11-16 11:49 ` Mel Gorman
2020-11-16 12:00 ` Mel Gorman
2020-11-16 12:53 ` Peter Zijlstra
2020-11-16 12:58 ` Peter Zijlstra
2020-11-16 15:29 ` Mel Gorman
2020-11-16 16:42 ` Mel Gorman
2020-11-16 16:49 ` Peter Zijlstra
2020-11-16 17:24 ` Mel Gorman
2020-11-16 17:41 ` Will Deacon
2020-11-16 12:46 ` Peter Zijlstra [this message]
2020-11-16 12:58 ` Mel Gorman
2020-11-16 13:11 ` Will Deacon
2020-11-16 13:37 ` Mel Gorman
2020-11-16 14:20 ` Peter Zijlstra
2020-11-16 15:52 ` Mel Gorman
2020-11-16 16:54 ` Peter Zijlstra
2020-11-16 17:16 ` Mel Gorman
2020-11-16 19:31 ` Mel Gorman
2020-11-17 8:30 ` [PATCH] sched: Fix data-race in wakeup Peter Zijlstra
2020-11-17 9:15 ` Will Deacon
2020-11-17 9:29 ` Peter Zijlstra
2020-11-17 9:46 ` Peter Zijlstra
2020-11-17 10:36 ` Will Deacon
2020-11-17 12:52 ` Valentin Schneider
2020-11-17 15:37 ` Valentin Schneider
2020-11-17 16:13 ` Peter Zijlstra
2020-11-17 19:32 ` Valentin Schneider
2020-11-18 8:05 ` Peter Zijlstra
2020-11-18 9:51 ` Valentin Schneider
2020-11-18 13:33 ` Marco Elver
2020-11-17 9:38 ` [PATCH] sched: Fix rq->nr_iowait ordering Peter Zijlstra
2020-11-17 11:43 ` Mel Gorman
2020-11-19 9:55 ` [tip: sched/urgent] " tip-bot2 for Peter Zijlstra
2020-11-17 12:40 ` [PATCH] sched: Fix data-race in wakeup Mel Gorman
2020-11-19 9:55 ` [tip: sched/urgent] " tip-bot2 for Peter Zijlstra
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