From: "Bouska, Zdenek" <zdenek.bouska@siemens.com>
To: Catalin Marinas <catalin.marinas@arm.com>
Cc: Thomas Gleixner <tglx@linutronix.de>,
Will Deacon <will@kernel.org>,
"linux-arm-kernel@lists.infradead.org"
<linux-arm-kernel@lists.infradead.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"Kiszka, Jan" <jan.kiszka@siemens.com>,
"linux-rt-users@vger.kernel.org" <linux-rt-users@vger.kernel.org>,
Nishanth Menon <nm@ti.com>, Puranjay Mohan <p-mohan@ti.com>
Subject: Re: Unfair qspinlocks on ARM64 without LSE atomics => 3ms delay in interrupt handling
Date: Mon, 27 Mar 2023 05:44:30 +0000 [thread overview]
Message-ID: <AS1PR10MB5675F191C6EC49ED8BEA9BECEB8B9@AS1PR10MB5675.EURPRD10.PROD.OUTLOOK.COM> (raw)
In-Reply-To: <ZB3XaNtVqGtYHHBw@arm.com>
>> So I confirmed that atomic operations from
>> arch/arm64/include/asm/atomic_ll_sc.h can be quite slow when they are
>> contested from second CPU.
>>
>> Do you think that it is possible to create fair qspinlock implementation
>> on top of atomic instructions supported by ARM64 version 8 (no LSE atomic
>> instructions) without compromising performance in the uncontested case?
>> For example ARM64 could have custom queued_fetch_set_pending_acquire
>> implementation same as x86 has in arch/x86/include/asm/qspinlock.h. Is the
>> retry loop in irq_finalize_oneshot() ok together with the current ARM64
>> cpu_relax() implementation for processor with no LSE atomic instructions?
>
>So is the queued_fetch_set_pending_acquire() where it gets stuck or the
>earlier atomic_try_cmpxchg_acquire() before entering on the slow path? I
>guess both can fail in a similar way.
For me it was stuck on queued_fetch_set_pending_acquire().
Zdenek Bouska
--
Siemens, s.r.o
Siemens Advanta Development
next prev parent reply other threads:[~2023-03-27 5:44 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-03-24 8:43 Bouska, Zdenek
2023-03-24 17:01 ` Catalin Marinas
2023-03-24 18:09 ` Will Deacon
2023-03-28 9:39 ` Bouska, Zdenek
2023-03-27 5:44 ` Bouska, Zdenek [this message]
2023-04-26 12:03 Bouska, Zdenek
2023-04-26 21:29 ` Thomas Gleixner
2023-04-27 9:38 ` Bouska, Zdenek
2023-04-27 10:06 ` Will Deacon
2023-04-27 13:14 ` Jan Kiszka
2023-04-27 13:45 ` Kurt Kanzenbach
2023-04-28 7:30 ` Sebastian Andrzej Siewior
2023-04-28 7:37 ` Kurt Kanzenbach
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