From: Frederic Weisbecker <frederic@kernel.org>
To: Mark Rutland <mark.rutland@arm.com>
Cc: linux-arm-kernel@lists.infradead.org, ardb@kernel.org,
bp@alien8.de, catalin.marinas@arm.com,
dave.hansen@linux.intel.com, james.morse@arm.com,
joey.gouly@arm.com, juri.lelli@redhat.com,
linux-kernel@vger.kernel.org, luto@kernel.org, mingo@redhat.com,
peterz@infradead.org, tglx@linutronix.de,
valentin.schneider@arm.com, will@kernel.org
Subject: Re: [PATCH v3 0/7] arm64 / sched/preempt: support PREEMPT_DYNAMIC with static keys
Date: Wed, 9 Feb 2022 20:58:27 +0100 [thread overview]
Message-ID: <20220209195827.GB557593@lothringen> (raw)
In-Reply-To: <20220209153535.818830-1-mark.rutland@arm.com>
On Wed, Feb 09, 2022 at 03:35:28PM +0000, Mark Rutland wrote:
> This series enables PREEMPT_DYNAMIC on arm64. To do so, it adds a new
> mechanism allowing the preemption functions to be enabled/disabled using
> static keys rather than static calls, with architectures selecting
> whether they use static calls or static keys.
>
> With non-inline static calls, each function call results in a call to
> the (out-of-line) trampoline which either tail-calls its associated
> callee or performs an early return.
>
> The key idea is that where we're only enabling/disabling a single
> callee, we can inline this trampoline into the start of the callee,
> using a static key to decide whether to return early, and leaving the
> remaining codegen to the compiler. The overhead should be similar to
> (and likely lower than) using a static call trampoline. Since most
> codegen is up to the compiler, we sidestep a number of implementation
> pain-points (e.g. things like CFI should "just work" as well as they do
> for any other functions).
>
> The bulk of the diffstat for kernel/sched/core.c is shuffling the
> PREEMPT_DYNAMIC code later in the file, and the actual additions are
> fairly trivial.
>
> I've given this very light build+boot testing so far.
>
> Since v1 [1]:
> * Rework Kconfig text to be clearer
> * Rework arm64 entry code
> * Clarify commit messages.
>
> Since v2 [2]:
> * Add missing includes
> * Always provide prototype for preempt_schedule()
> * Always provide prototype for preempt_schedule_notrace()
> * Fix __cond_resched() to default to disabled
> * Fix might_resched() to default to disabled
> * Clarify example in commit message
Acked-by: Frederic Weisbecker <frederic@kernel.org>
Thanks!
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next prev parent reply other threads:[~2022-02-09 19:59 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-02-09 15:35 [PATCH v3 0/7] arm64 / sched/preempt: support PREEMPT_DYNAMIC with static keys Mark Rutland
2022-02-09 15:35 ` [PATCH v3 1/7] sched/preempt: move PREEMPT_DYNAMIC logic later Mark Rutland
2022-02-09 15:35 ` [PATCH v3 2/7] sched/preempt: refactor sched_dynamic_update() Mark Rutland
2022-02-09 15:35 ` [PATCH v3 3/7] sched/preempt: simplify irqentry_exit_cond_resched() callers Mark Rutland
2022-02-09 15:35 ` [PATCH v3 4/7] sched/preempt: decouple HAVE_PREEMPT_DYNAMIC from GENERIC_ENTRY Mark Rutland
2022-02-09 15:35 ` [PATCH v3 5/7] sched/preempt: add PREEMPT_DYNAMIC using static keys Mark Rutland
2022-02-09 17:48 ` Frederic Weisbecker
2022-02-10 10:27 ` Mark Rutland
2022-02-10 15:59 ` Frederic Weisbecker
2022-02-09 15:35 ` [PATCH v3 6/7] arm64: entry: centralize premeption decision Mark Rutland
2022-02-09 18:10 ` Catalin Marinas
2022-02-10 9:19 ` Mark Rutland
2022-02-09 15:35 ` [PATCH v3 7/7] arm64: support PREEMPT_DYNAMIC Mark Rutland
2022-02-09 18:13 ` Catalin Marinas
2022-02-09 19:57 ` Frederic Weisbecker
2022-02-10 9:38 ` Mark Rutland
2022-02-10 12:00 ` Mark Rutland
2022-02-10 15:58 ` Frederic Weisbecker
2022-02-09 19:58 ` Frederic Weisbecker [this message]
2022-02-10 9:29 ` [PATCH v3 0/7] arm64 / sched/preempt: support PREEMPT_DYNAMIC with static keys Ard Biesheuvel
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