[dm-devel] dm kcopyd: Increase sub-job size to 512KiB
Nikos Tsironis
ntsironis at arrikto.com
Tue Jul 16 13:59:38 UTC 2019
On 7/15/19 9:22 PM, Mike Snitzer wrote:
> On Fri, Jul 12 2019 at 9:45am -0400,
> Nikos Tsironis <ntsironis at arrikto.com> wrote:
>
>> Hi Mike,
>>
>> A kind reminder about this patch. Do you require any changes or will you
>> merge it as is?
>
> I think we need changes to expose knob(s) to tune this value on a global
> _and_ device level via sysfs. E.g.:
>
> 1) dm_mod module param for global
> 2) but also allow a per-device override, like:
> echo 512 > /sys/block/dm-X/dm/kcopyd_subjob_size
>
Hi Mike,
Thanks for your feedback. I agree, this sounds like the best thing to do.
> 1 is super easy and is a start. Layering in 2 is a bit more involved.
Maybe I could help with (2). We could discuss about it and how you think
it's best to do it and then I could proceed with an implementation.
Please let me know what you think.
>
> In hindsight (given how risk-averse I am on changing the default) I
> should've kept the default 128 but allowed override with modparam
> dm_mod.kcopyd_subjob_size=1024
>
> Would this be an OK first step?
Yes, this would be great.
>
> If so, we're still in the 5.3 merge window, I'll see what I can do.
Shall I proceed with a patch adding the dm_mod.kcopyd_subjob_size
modparam?
Thanks,
Nikos
>
> Thanks,
> Mike
>
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