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From: Gaurav Kohli <gkohli@codeaurora.org>
To: Will Deacon <will@kernel.org>
Cc: linux-arm-kernel@lists.infradead.org, maz@kernel.org,
	linux-kernel@vger.kernel.org, linux-arm-msm@vger.kernel.org,
	neeraju@codeaurora.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

WARNING: multiple messages have this Message-ID (diff)
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

_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

  reply	other threads:[~2020-08-12 14:17 UTC|newest]

Thread overview: 20+ 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 ` Gaurav Kohli
2019-04-15 16:40 ` [PATCH] nvmem: core: add NVMEM_SYSFS Kconfig Srinivas Kandagatla
2020-08-04 14:14   ` Gaurav Kohli
2019-04-16  5:19   ` Gaurav Kohli
2019-04-16  9:34     ` Mika Westerberg
2019-04-16  9:44       ` Srinivas Kandagatla
2019-04-16  9:47         ` Mika Westerberg
2020-08-04 14:26   ` Gaurav Kohli
2020-08-04 14:26     ` Gaurav Kohli
2020-08-04 14:14 ` [PATCH] nvmem: core: add support to NVMEM_NO_SYSFS_ENTRY Gaurav Kohli
2020-08-04 14:14   ` Gaurav Kohli
2020-08-04 14:25   ` Gaurav Kohli
2020-08-04 14:25     ` Gaurav Kohli
2020-08-11  4:48 ` [PATCH] arm64: Skip apply SSBS call for non SSBS system Gaurav Kohli
2020-08-11  4:48   ` Gaurav Kohli
2020-08-12 13:30 ` Will Deacon
2020-08-12 13:30   ` Will Deacon
2020-08-12 14:15   ` Gaurav Kohli [this message]
2020-08-12 14:15     ` Gaurav Kohli

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