3. TWEAK­ING THE CPU GOV­ER­NOR

HWM (Malaysia) - - LEARN -

In­creas­ing the min­i­mum fre­quency of the CPU will re­sult in less per­for­mance slow­downs, while in­creas­ing the max­i­mum will al­low the CPU to ramp higher un­der loads such as gam­ing. The drop-down menu of­fers fixed over­clocked val­ues, which sim­pli­fies things by lim­it­ing your op­tions. We were gen­er­ally com­fort­able go­ing for a max­i­mum fre­quency of 2,304MHz for our de­vice.

You can tweak the same pa­ram­e­ters for the more power-ef­fi­cient Cor­tex A53 cores as well. Less-de­mand­ing tasks like web brows­ing will pri­or­i­tize th­ese cores over the A57s, so if you think your phone could be speed­ier in this area, over­clock­ing th­ese cores may help.

For volt­age con­trol, use the Synapse app to set the volt­ages for the in­di­vid­ual CPU steps. In gen­eral, lower clock speeds (< 1,000MHz) could do with around a 25mV un­der­volt to con­serve power. Synapse com­putes the in­creased volt­age at the over­clocked fre­quen­cies for you, and we didn’t see a need to de­vi­ate from those val­ues. But if your over­clock is un­sta­ble, boost­ing the volt­ages slightly may help. Ker­nel Adi­u­tor also lets you change the CPU gov­er­nor for both big and LIT­TLE core clus­ters. This is what con­trols how the var­i­ous cores re­spond to changes in user de­mand. There are just two op­tions to choose from here: in­ter­ac­tive and per­for­mance.

The de­fault in­ter­ac­tive gov­er­nor dy­nam­i­cally scales CPU clock speeds in re­sponse to user work­loads. It is also ca­pa­ble of uti­liz­ing in­ter­me­di­ate CPU fre­quen­cies, which makes it a fairly ver­sa­tile gov­er­nor that bal­ances both per­for­mance and bat­tery life.

On the other hand, the per­for­mance gov­er­nor sim­ply locks the phone’s CPU at max­i­mum fre­quency. If you’re go­ing to want to do this at all, it makes more sense to ap­ply this for the LIT­TLE cores as you’ll get faster gen­eral per­for­mance while not quite drain­ing your bat­tery with the more power-hun­gry big cores.

The Gov­er­nor Tun­ables op­tion is not avail­able for the per­for­mance gov­er­nor, but you have the op­tion to fur­ther tweak the in­ter­ac­tive gov­er­nor. The op­tions may seem a lot to grap­ple with, but you can just pay at­ten­tion to the fol­low­ing (along with tips as to what they do): • his­peed_freq - CPU fre­quency (in Hz) to bump to when CPU load above go_his­peed_load. In­creas­ing this boosts per­for­mance. • go_his­peed_load - Go to hi speed when CPU load is at or above this value. Low­er­ing this value will cause the CPU to ramp up more of­ten, and vice versa. • min_sam­ple_­time - The min­i­mum amount of time (in μs) to spend at a fre­quency be­fore CPU can ramp down. In­creas­ing this value in­creases the num­ber of suc­ces­sive tasks you can per­form be­fore the CPU scales back down, re­duc­ing fre­quency bounc­ing. • timer_rate - Sam­ple rate (in μs) for reeval­u­at­ing CPU load when sys­tem is not idle. De­creas­ing this value may al­low CPU to re­spond to sud­den loads more quickly.

DE­CEM­BER 2015

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HWM

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