[sles-beta] SLES 12 SP1 BETA3 - tickless kernel

[Laxman, Mahendra]

Hi Libor,

It is great to here about that.. 

CONFIG_NO_HZ_FULL=y will also enhance power-saving as well.
I think it will be beneficial to have it in generic kernel as well. 
Is there any reason that we can't have this in generic kernel?

BTW RHEL generic kernel already having this enabled.

Regards,
Mahendra. 
________________________________________
From: Libor Pechacek [lpechacek at suse.com]
Sent: 25 September 2015 15:20
To: Laxman, Mahendra
Cc: sles-beta at lists.suse.com
Subject: Re: [sles-beta]  SLES 12 SP1 BETA3 - tickless kernel

Hello Mahendra,

A kernel with CONFIG_NO_HZ_FULL=y enabled is part of the upcoming SLERT 12 SP1.
Lab test results with sysjitter and the latest SLERT development snapshot
show equally good results as your ones.

Regards,
                Libor Pechacek

On Fri 25-09-15 06:22:13, Laxman, Mahendra wrote:
> Hi all,
>
> I would like to have tickless mode enable in SLES12 SP1 kernel to reduce the
> system jitter produced by the clock interrupts.
> I did test this behavior on the kernel version 3.12.47-2-default and it
> reduced a significant amount of jitter.
> The jitter was measured using sysjitter-1.3
> [http://www.openonload.org/download.html] with command './sysjitter --runtime
> 20 300'.
> Only the last line of the test result is given below which represent the
> percentage jitter caused  through 20s test duration and the lower values are
> better.
>
> without tickless mode (default Kernel with boot parameters:  isolcpus=1-15 )
> core_i: 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
> int_total(%): 0.152 0.113 0.113 0.113 0.116 0.115 0.113 0.116 0.140 0.120 0.122 0.119 0.120 0.122 0.119 0.119
>
> with tickless mode (Kernel compiled with CONFIG_NO_HZ_FULL=y  and boot parameters: nohz_full=1-15 isolcpus=1-15 rcu_nocbs=1-15)
> core_i: 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
> int_total(%): 0.365 0.015 0.017 0.015 0.019 0.015 0.015 0.019 0.004 0.004 0.004 0.004 0.003 0.004 0.004 0.004
>
> Full test output is also attached herewith.
>
>
> What is the possibility of having tickless mode enabled?
>
>
> Thanks & Regards,
> Mahendra.


--
Libor Pechacek
SUSE Labs


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