Brett I. Holcomb wrote:
> Out of curiosity and so I can learn. Why did you suggest CONFIG_HZ be
> set to 100 (IIRC default is 250) and also what exactly is it supposed to
> do for you. We did not have it before.
>
In the past was fixed to 100Hz, then to 1000 appeared, now there is a
third option for 250, the current default and a good compromise.
An home system become more responsive with a higher frequency.
cpu and interrupt timings become lower with a lower frequency, so it's
better for a server system. Expecially a multi processor one.
> Also what about CONFIG_PREMPT being none? The help mentions it is for
> low latency.
>> CONFIG_HZ=100
>> CONFIG_PREEMPT_NONE=y
>> IOSCHED_AS || IOSCHED_DEADLINE || IOSCHED_CFQ
>>
Preemption permit to interrupt kernel processes, providing a still more
responsive kernel. Good if you're hering music, playing videos and such
but not very interesting for a server.
The third option is the "scheduler" (IOSCHED_*) how the kernel access
the disk. this has been discussed in great detail over the net.
Quoting the kernel help here, since it's short and explanatory.
--------- quote ---------
CONFIG_IOSCHED_AS:
The anticipatory I/O scheduler is the default disk scheduler. It is
generally a good choice for most environments, but is quite large and
complex when compared to the deadline I/O scheduler, it can also be
slower in some cases especially some database loads.
Symbol: IOSCHED_AS [=y]
Prompt: Anticipatory I/O scheduler
Defined at drivers/block/Kconfig.iosched:14
Location:
-> Device Drivers
-> Block devices
-> IO Schedulers
--------- quote ---------
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