From: David Laight <david.laight.linux@gmail.com>
To: Ankur Arora <ankur.a.arora@oracle.com>
Cc: linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org,
linux-arm-kernel@lists.infradead.org, linux-pm@vger.kernel.org,
bpf@vger.kernel.org, arnd@arndb.de, catalin.marinas@arm.com,
will@kernel.org, peterz@infradead.org, akpm@linux-foundation.org,
mark.rutland@arm.com, harisokn@amazon.com, cl@gentwo.org,
ast@kernel.org, rafael@kernel.org, daniel.lezcano@linaro.org,
memxor@gmail.com, zhenglifeng1@huawei.com,
xueshuai@linux.alibaba.com, joao.m.martins@oracle.com,
boris.ostrovsky@oracle.com, konrad.wilk@oracle.com
Subject: Re: [PATCH v9 01/12] asm-generic: barrier: Add smp_cond_load_relaxed_timeout()
Date: Sat, 14 Feb 2026 11:31:22 +0000 [thread overview]
Message-ID: <20260214113122.70627a8b@pumpkin> (raw)
In-Reply-To: <87tsvj6hwf.fsf@oracle.com>
On Fri, 13 Feb 2026 20:58:08 -0800
Ankur Arora <ankur.a.arora@oracle.com> wrote:
> David Laight <david.laight.linux@gmail.com> writes:
...
> > Plus the cost of evaluating cond_expr 200 times.
> > I guess that isn't expected to contain a PCIe read :-)
>
> :). Good point. I'll see if I can add something like "when polling on
> a memory address".
I've only timed PCIe reads into an fpga (Cyclone V) target, but those
are about 1 micro-second - which is a lot of clocks.
Hard logic will be somewhat faster - but still slow.
There might be other places where 200 isn't a good value.
Perhaps add an extra #define that drops in the loop count?
David
next prev parent reply other threads:[~2026-02-14 11:31 UTC|newest]
Thread overview: 33+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-02-09 2:31 [PATCH v9 00/12] barrier: Add smp_cond_load_{relaxed,acquire}_timeout() Ankur Arora
2026-02-09 2:31 ` [PATCH v9 01/12] asm-generic: barrier: Add smp_cond_load_relaxed_timeout() Ankur Arora
2026-02-09 4:57 ` Randy Dunlap
2026-02-10 5:52 ` Ankur Arora
2026-02-11 15:39 ` Catalin Marinas
2026-02-11 22:17 ` Ankur Arora
2026-02-12 9:56 ` David Laight
2026-02-14 4:58 ` Ankur Arora
2026-02-14 11:31 ` David Laight [this message]
2026-02-18 6:33 ` Ankur Arora
2026-02-09 2:31 ` [PATCH v9 02/12] arm64: barrier: Support smp_cond_load_relaxed_timeout() Ankur Arora
2026-02-11 15:54 ` Catalin Marinas
2026-02-11 22:57 ` Ankur Arora
2026-02-09 2:31 ` [PATCH v9 03/12] arm64/delay: move some constants out to a separate header Ankur Arora
2026-02-11 16:01 ` Catalin Marinas
2026-02-09 2:31 ` [PATCH v9 04/12] arm64: support WFET in smp_cond_load_relaxed_timeout() Ankur Arora
2026-02-11 17:11 ` Catalin Marinas
2026-02-11 23:13 ` Ankur Arora
2026-02-09 2:31 ` [PATCH v9 05/12] arm64: rqspinlock: Remove private copy of smp_cond_load_acquire_timewait() Ankur Arora
2026-02-09 2:31 ` [PATCH v9 06/12] asm-generic: barrier: Add smp_cond_load_acquire_timeout() Ankur Arora
2026-02-09 4:59 ` Randy Dunlap
2026-02-09 2:31 ` [PATCH v9 07/12] atomic: Add atomic_cond_read_*_timeout() Ankur Arora
2026-02-11 17:25 ` Catalin Marinas
2026-02-09 2:31 ` [PATCH v9 08/12] locking/atomic: scripts: build atomic_long_cond_read_*_timeout() Ankur Arora
2026-02-11 17:41 ` Catalin Marinas
2026-02-09 2:31 ` [PATCH v9 09/12] bpf/rqspinlock: switch check_timeout() to a clock interface Ankur Arora
2026-02-09 3:05 ` bot+bpf-ci
2026-02-09 2:31 ` [PATCH v9 10/12] bpf/rqspinlock: Use smp_cond_load_acquire_timeout() Ankur Arora
2026-02-09 2:31 ` [PATCH v9 11/12] sched: add need-resched timed wait interface Ankur Arora
2026-02-09 3:05 ` bot+bpf-ci
2026-02-09 2:31 ` [PATCH v9 12/12] cpuidle/poll_state: Wait for need-resched via tif_need_resched_relaxed_wait() Ankur Arora
2026-02-10 16:55 ` Rafael J. Wysocki
2026-02-11 0:29 ` Ankur Arora
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