From: Gaurav Kohli <gkohli@codeaurora.org>
To: Will Deacon <will@kernel.org>
Cc: maz@kernel.org, neeraju@codeaurora.org,
linux-kernel@vger.kernel.org,
linux-arm-kernel@lists.infradead.org,
linux-arm-msm@vger.kernel.org
Subject: Re: [PATCH] arm64: Skip apply SSBS call for non SSBS system
Date: Wed, 12 Aug 2020 19:45:12 +0530 [thread overview]
Message-ID: <5b1ad0e0-bbe7-9869-ee19-1b62023203ed@codeaurora.org> (raw)
In-Reply-To: <20200812133043.GA8924@willie-the-truck>
On 8/12/2020 7:00 PM, Will Deacon wrote:
> On Tue, Aug 04, 2020 at 07:44:42PM +0530, Gaurav Kohli wrote:
>> In a system where no cpu's implement SSBS, for
>> them no need to set pstate. This might help to save
>> few cpu cycles during context switch.
>>
>> Signed-off-by: Gaurav Kohli <gkohli@codeaurora.org>
>>
>> diff --git a/arch/arm64/kernel/process.c b/arch/arm64/kernel/process.c
>> index 6089638..79f80f1 100644
>> --- a/arch/arm64/kernel/process.c
>> +++ b/arch/arm64/kernel/process.c
>> @@ -477,6 +477,13 @@ static void ssbs_thread_switch(struct task_struct *next)
>> struct pt_regs *regs = task_pt_regs(next);
>>
>> /*
>> + * For Targets which don't have SSBS support, they
>> + * can return from here.
>> + */
>> + if (!IS_ENABLED(CONFIG_ARM64_SSBD))
>> + return;
>
> Does this actually make a measurable difference?
>
> Will
>
Hi Will,
While doing code review between older kernel and latest kernel for
context switch case, there i have found this and thought it is good to
have for non-ssbs system to return early(as this might improve).
Please let me know if you want to run some tests.
Regards
Gaurav
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prev parent reply other threads:[~2020-08-12 14:17 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-08-04 14:14 [PATCH] arm64: Skip apply SSBS call for non SSBS system Gaurav Kohli
2020-08-04 14:14 ` [PATCH] nvmem: core: add support to NVMEM_NO_SYSFS_ENTRY Gaurav Kohli
2020-08-04 14:25 ` Gaurav Kohli
2020-08-04 14:14 ` [PATCH] nvmem: core: add NVMEM_SYSFS Kconfig Gaurav Kohli
2020-08-04 14:26 ` Gaurav Kohli
2020-08-11 4:48 ` [PATCH] arm64: Skip apply SSBS call for non SSBS system Gaurav Kohli
2020-08-12 13:30 ` Will Deacon
2020-08-12 14:15 ` Gaurav Kohli [this message]
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