Re: [PATCH 0/2] ext4: Fix performance regression with mballoc

Stefan Wahren
2022-08-24T10:17:31Z

Hi Jan,

Am 23.08.22 um 22:15 schrieb Jan Kara:
> Hello,
>
> So I have implemented mballoc improvements to avoid spreading allocations
> even with mb_optimize_scan=1. It fixes the performance regression I was able
> to reproduce with reaim on my test machine:
>
> mb_optimize_scan=0 mb_optimize_scan=1 patched
> Hmean disk-1 2076.12 ( 0.00%) 2099.37 ( 1.12%) 2032.52 ( -2.10%)
> Hmean disk-41 92481.20 ( 0.00%) 83787.47 * -9.40%* 90308.37 ( -2.35%)
> Hmean disk-81 155073.39 ( 0.00%) 135527.05 * -12.60%* 154285.71 ( -0.51%)
> Hmean disk-121 185109.64 ( 0.00%) 166284.93 * -10.17%* 185298.62 ( 0.10%)
> Hmean disk-161 229890.53 ( 0.00%) 207563.39 * -9.71%* 232883.32 * 1.30%*
> Hmean disk-201 223333.33 ( 0.00%) 203235.59 * -9.00%* 221446.93 ( -0.84%)
> Hmean disk-241 235735.25 ( 0.00%) 217705.51 * -7.65%* 239483.27 * 1.59%*
> Hmean disk-281 266772.15 ( 0.00%) 241132.72 * -9.61%* 263108.62 ( -1.37%)
> Hmean disk-321 265435.50 ( 0.00%) 245412.84 * -7.54%* 267277.27 ( 0.69%)
>
> Stefan, can you please test whether these patches fix the problem for you as
> well? Comments & review welcome.

i tested the whole series against 5.19 and 6.0.0-rc2. In both cases the
update process succeed which is a improvement, but the download + unpack
duration ( ~ 7 minutes ) is not as good as with mb_optimize_scan=0 ( ~ 1
minute ).

Unfortuntately i don't have much time this week and next week i'm in
holidays.

Just a question, my tests always had MBCACHE=y . Is it possible that the
mb_optimize_scan is counterproductive for MBCACHE in this case?

I'm asking because before the download the update script removes the
files from the previous update process which already cause a high load.

Best regards

>
> Honza