On 7/16/19 5:14 PM, Mike Snitzer wrote: > On Tue, Jul 16 2019 at 10:11am -0400, > Mike Snitzer <snitzer@xxxxxxxxxx> wrote: > >> On Tue, Jul 16 2019 at 9:59am -0400, >> Nikos Tsironis <ntsironis@xxxxxxxxxxx> wrote: >> >>> On 7/15/19 9:22 PM, Mike Snitzer wrote: >>>> On Fri, Jul 12 2019 at 9:45am -0400, >>>> Nikos Tsironis <ntsironis@xxxxxxxxxxx> 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? >> >> Sure. And it could be that we won't need 2. >> >> Ideally the default would work for every setup. Less knobs the better. >> But as a stop-gap I think we need to expose a knob that allows override. >> >> Thinking further, I don't think changing the default to 512K is too >> risky (famous last words). So please just update your original patch to >> include the modparam so that users can get the old 64K back if needed. >> >> BTW, the param name should probably be "kcopyd_subjob_size_kb" to >> reflect the value is KB. > > One other thing: not sure what the max should be on this > modparam.. maybe 1024K? I think 1024K is a reasonable maximum value. I will add the "kcopyd_subjob_size_kb" modparam and send a second version of the patch. Thanks, Nikos > > Mike > -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
