[lustre-discuss] More issues with cur_grant_bytes

[Aaron Knister]

Hi Kevin, Meg, Nathan,

I'm interested in some of the details about how you're hitting this with 
an eye to reproducing. Could you share any details about the following:

- Interconnect

- Client count

- Workload

Thanks!

-Aaron

On 12/8/20 1:46 PM, Kevin M. Hildebrand wrote:
> We appear to be tripping over the same issues reported recently by 
> Tung-Han Hsieh and Simon Guilbault, namely that cur_grant_bytes is 
> being reduced to a very small value and causing abysmal performance.
>
> For example, OSTs 0, 1, and 4 are having poor performance on this 
> client running Lustre 2.12.5:
> # lctl get_param osc.*.cur_grant_bytes
> osc.lustre10-OST0000-osc-ffff8e47dc02a800.cur_grant_bytes=802542
> osc.lustre10-OST0001-osc-ffff8e47dc02a800.cur_grant_bytes=924204
> osc.lustre10-OST0002-osc-ffff8e47dc02a800.cur_grant_bytes=11076653
> osc.lustre10-OST0003-osc-ffff8e47dc02a800.cur_grant_bytes=108098653
> osc.lustre10-OST0004-osc-ffff8e47dc02a800.cur_grant_bytes=797559
> osc.lustre10-OST0005-osc-ffff8e47dc02a800.cur_grant_bytes=4719258
> osc.lustre10-OST0006-osc-ffff8e47dc02a800.cur_grant_bytes=4898757
> osc.lustre10-OST0007-osc-ffff8e47dc02a800.cur_grant_bytes=10747719
> osc.lustre10-OST0008-osc-ffff8e47dc02a800.cur_grant_bytes=315019599
> osc.lustre10-OST0009-osc-ffff8e47dc02a800.cur_grant_bytes=597198336
> osc.lustre10-OST000a-osc-ffff8e47dc02a800.cur_grant_bytes=278803109
> osc.lustre10-OST000b-osc-ffff8e47dc02a800.cur_grant_bytes=1335800831
> osc.lustre10-OST000c-osc-ffff8e47dc02a800.cur_grant_bytes=795705344
> osc.lustre10-OST000d-osc-ffff8e47dc02a800.cur_grant_bytes=1335052800
> osc.lustre10-OST000e-osc-ffff8e47dc02a800.cur_grant_bytes=474925228
> osc.lustre10-OST000f-osc-ffff8e47dc02a800.cur_grant_bytes=1424795647
>
> From the previous discussion, the recommendation seems to have been to 
> run
> lctl set_param -P osc.*.grant_shrink=0 on the client.  Are there any 
> downsides to doing this?
> Should I just blindly do this on all of my Lustre clients?
>
> A little more insight into what's going on here would be appreciated.
>
> Thanks,
> Kevin
>
> --
> Kevin Hildebrand
> University of Maryland
> Division of IT