| From: |
| Mark Rutland <mark.rutland-AT-arm.com> |
| To: |
| linux-arm-kernel-AT-lists.infradead.org |
| Subject: |
| [PATCH v2 0/7] arm64 / sched/preempt: support PREEMPT_DYNAMIC with static keys |
| Date: |
| Fri, 04 Feb 2022 15:05:50 +0000 |
| Message-ID: |
| <20220204150557.434610-1-mark.rutland@arm.com> |
| Cc: |
| ardb-AT-kernel.org, bp-AT-alien8.de, catalin.marinas-AT-arm.com, dave.hansen-AT-linux.intel.com, frederic-AT-kernel.org, james.morse-AT-arm.com, joey.gouly-AT-arm.com, juri.lelli-AT-redhat.com, linux-kernel-AT-vger.kernel.org, luto-AT-kernel.org, mark.rutland-AT-arm.com, mingo-AT-redhat.com, peterz-AT-infradead.org, tglx-AT-linutronix.de, valentin.schneider-AT-arm.com, will-AT-kernel.org |
| Archive-link: |
| Article |
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.
[1] https://lore.kernel.org/all/20211109172408.49641-1-mark.r...
Mark Rutland (7):
sched/preempt: move PREEMPT_DYNAMIC logic later
sched/preempt: refactor sched_dynamic_update()
sched/preempt: simplify irqentry_exit_cond_resched() callers
sched/preempt: decouple HAVE_PREEMPT_DYNAMIC from GENERIC_ENTRY
sched/preempt: add PREEMPT_DYNAMIC using static keys
arm64: entry: centralize premeption decision
arm64: support PREEMPT_DYNAMIC
arch/Kconfig | 37 +++-
arch/arm64/Kconfig | 1 +
arch/arm64/include/asm/preempt.h | 16 +-
arch/arm64/kernel/entry-common.c | 28 ++-
arch/x86/Kconfig | 2 +-
arch/x86/include/asm/preempt.h | 10 +-
include/linux/entry-common.h | 15 +-
include/linux/kernel.h | 7 +-
include/linux/sched.h | 10 +-
kernel/entry/common.c | 22 +-
kernel/sched/core.c | 346 ++++++++++++++++++-------------
11 files changed, 322 insertions(+), 172 deletions(-)
--
2.30.2
