Messages in this thread | | | Subject | v5.8+ powersave governor breakage? | From | Mike Galbraith <> | Date | Sun, 01 Nov 2020 17:23:59 +0100 |
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Greetings,
As you can see in the data below, my i4790 box used to default to the powersave governor despite CONFIG_CPU_FREQ_DEFAULT_GOV_ONDEMAND=y, and disallowed switching to ondemand. Post 5.8, powersave locks in at the lowest freq available, and while ondemand becomes the default, it takes a cross core scheduling performance hit compared to previous powersave.
On a positive note, schedutil, which I used to have cause to avoid, seems to have improved a lot while I wasn't looking, and now actually improving cross core performance a wee bit. Seems I should configure stable 5.[89] kernels to use it as well.
taskset 0xc pipe-test 1
CONFIG_CPU_FREQ_DEFAULT_GOV_ONDEMAND=y defaults to 5.4.74 2.183264 usecs/loop -- avg 2.179480 917.7 KHz powersave, ondemand not allowed 5.5.19 2.184331 usecs/loop -- avg 2.179776 917.5 KHz powersave, ondemand not allowed 5.6.19 2.198156 usecs/loop -- avg 2.204380 907.3 KHz powersave, ondemand not allowed 5.7.19 2.230582 usecs/loop -- avg 2.231981 896.1 KHz powersave, ondemand not allowed 5.8.17 3.203949 usecs/loop -- avg 3.207272 623.6 KHz ondemand 5.8.17 12.840411 usecs/loop -- avg 12.898500 155.1 KHz ondemand -> powersave 5.9.2 3.024442 usecs/loop -- avg 3.040023 657.9 KHz ondemand 5.9.2 12.348519 usecs/loop -- avg 12.299751 162.6 KHz ondemand -> powersave CONFIG_CPU_FREQ_DEFAULT_GOV_SCHEDUTIL=y due to db865272d9c4 5.10.gc2dc4c0 2.121057 usecs/loop -- avg 2.121487 942.7 KHz schedutil note: 4.0 GHz perfect! 5.10.gc2dc4c0 2.987989 usecs/loop -- avg 2.988658 669.2 KHz schedutil -> ondemand note: 2.9 GHz not so perfect 5.10.gc2dc4c0 12.447348 usecs/loop -- avg 12.475363 160.3 KHz schedutil -> powersave note: 800 MHz heeelp meee 5.10.gc2dc4c0 2.135548 usecs/loop -- avg 2.137868 935.5 KHz schedutil -> performance note: 4.0 GHz (obviously)
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