Now that HTC has released the source code for the gingerbread and devs are now making gingerbread kernels, i figured that this is a good time to put up a guide to help those who do not understand what a kernel is and what it can do.
one of the reasons that we all rooted our phones is so that we can enjoy better battery life then the non rooted phones. one way we can do this is to use a custom kernel.
what is a kernel? a kernel basically communicates with and adjusts the voltage between the hardware(battery) and software(either sense or aosp) of your phone according to frequency. how much voltage a kernel decides to provide to and from your phone and at what frequency will depend on the type of kernels.
there are two main type of kernels:
cfs (completely fair scheduler): it tends to be more fair on an even distribution of voltage to all running processes (think apps). it is mainly designed for your typical standard tasks. things like using the web or text messaging can all be handled by cfs kernels. it tends to be better at giving the best battery life.
bfs (brain f*ck scheduler): a kernel that is more focused on certain running processes like apps. the main purpose is to run apps that need more voltage and to run them more smoothly at the expense of other processes which tend to make the phone laggy. however, it can make game play run better.
sub category
havs (hybrid adaptive voltage scaling):there are different degrees of havs kernels. they run from more havs to less havs to no havs kernels. these kernels will have a variable range of voltages as the system fluctuates according to need. they tend to err on lowering the voltage on processes that does not need the set (static) voltage for that process. basically these kernels have a max and min and will adjust the voltages accordingly to the process at hand.
no havs: since havs is not at work on these kernels, the default then is in the form of static voltage scaling which is an even amount of voltage that does not fluctuate regardless of what process is running. so even smaller tasks will get the same amount of voltage and thus potentially wasting battery life.
static undervolting:when there isn't any havs implemented on the kernel then the kernel will be using static undervolting. for each cpu speed there is a set voltage number (it is always gonna be a constant number) assigned that are lower then the normal voltage.
sbc (superior battery charging):this is a type of trickle charging that is slower in its charge and is best done overnight. it is supposed to prevent that initial 10% drop off charge. the idea is that as the voltage is pushed into the battery while charging very slowly, the battery will stay cool. by keeping the battery cool you will avoid plating where lithium ions are deposited on the anode of the battery in metallic form vs the ionic form. once lithium is metallic, it can no longer transfer electricity so obviously you want to avoid plating as much as possible.
it also supposed to charge the battery past its normal 100%. your battery indicator has a certain value for what it deems to be 100%. however the sbc charge allows the battery to charge past that point. there was concern that the sbc kernel will overcharge the battery and thus kill the life of the battery and or it can cause it to explode. now in the past, if you look around the net, you will see that people were concerned for their phones exploding due to the use of sbc kernels. though there were a few cases (supposedly) of exploding phones early on, there has not been any reported that i know of since. and yes sbc kernels may degrade your battery down faster then non sbc kernels. however, i think that the trade off of getting better battery life is better then having a battery last longer. batteries are cheap these days anyways.
every custom rom comes with its own kernel which in most cases is just stock. in order to switch kernels, all you would have to do is just flash a custom one of your choice. just make sure that you make a nandroid backup first then wipe dalvik cache and cache and flash away.
kernels are designed to work the two main types of rom. there are one for sense and then there are ones for AOSP(Android Open Source Project). they also make universal kernels that works on both AOSP and sense. however, the AOSP kernels will not work on a sense rom and vice versa. Also the new gingerbread roms will not work with froyo kernels. the main thing is to make sure that you know what kernel you are flashing and what rom you have.
1.download the kernel of your choice
2.transfer the file over to the card
3.go into recovery
4.make a nandroid backup
5.wipe dalvik cache and cache
6.flash the zip file
7.reboot.
what is setcpu? it is an app found on the market that works on most android devices. its main purpose is to set and maintain cpu frequencies. also you will need a custom kernel if you want to over and underclock your phone using setcpu.
not all phones have the same threshold for overclocking so you have to be careful on how high you set the frequency. make sure that the set on boot found on the main screen is not checked. if you overclock to high then your phone will not work right. it will seize up and could cause a reboot. if you have set on boot at that level then you will get a bootloop that is hard to get out of. once you know at what point your phone is overclocked but stable, then you can go ahead and set it on boot.
as far as profiles go, i would bot recommend having too many. it is counterproductive and if you have a lot of profiles, then setcpu will then be working that much harder to monitor and maintain those profiles. usually a screen off profile is good enough to help save battery.
scaling governors control exactly how the cpu scales between your "max" and "min" set frequencies.
here is a great explanantion of some of the governors out there. thanx NaterTots!!!!!
Links
you can download setcpu from the market.
checkout this guide:setcpu guide
if you want to read more here are some threads you might want to checkout:
[GUIDE]
one of the reasons that we all rooted our phones is so that we can enjoy better battery life then the non rooted phones. one way we can do this is to use a custom kernel.
Kernels
what is a kernel? a kernel basically communicates with and adjusts the voltage between the hardware(battery) and software(either sense or aosp) of your phone according to frequency. how much voltage a kernel decides to provide to and from your phone and at what frequency will depend on the type of kernels.
there are two main type of kernels:
cfs (completely fair scheduler): it tends to be more fair on an even distribution of voltage to all running processes (think apps). it is mainly designed for your typical standard tasks. things like using the web or text messaging can all be handled by cfs kernels. it tends to be better at giving the best battery life.
bfs (brain f*ck scheduler): a kernel that is more focused on certain running processes like apps. the main purpose is to run apps that need more voltage and to run them more smoothly at the expense of other processes which tend to make the phone laggy. however, it can make game play run better.
sub category
havs (hybrid adaptive voltage scaling):there are different degrees of havs kernels. they run from more havs to less havs to no havs kernels. these kernels will have a variable range of voltages as the system fluctuates according to need. they tend to err on lowering the voltage on processes that does not need the set (static) voltage for that process. basically these kernels have a max and min and will adjust the voltages accordingly to the process at hand.
no havs: since havs is not at work on these kernels, the default then is in the form of static voltage scaling which is an even amount of voltage that does not fluctuate regardless of what process is running. so even smaller tasks will get the same amount of voltage and thus potentially wasting battery life.
static undervolting:when there isn't any havs implemented on the kernel then the kernel will be using static undervolting. for each cpu speed there is a set voltage number (it is always gonna be a constant number) assigned that are lower then the normal voltage.
sbc (superior battery charging):this is a type of trickle charging that is slower in its charge and is best done overnight. it is supposed to prevent that initial 10% drop off charge. the idea is that as the voltage is pushed into the battery while charging very slowly, the battery will stay cool. by keeping the battery cool you will avoid plating where lithium ions are deposited on the anode of the battery in metallic form vs the ionic form. once lithium is metallic, it can no longer transfer electricity so obviously you want to avoid plating as much as possible.
it also supposed to charge the battery past its normal 100%. your battery indicator has a certain value for what it deems to be 100%. however the sbc charge allows the battery to charge past that point. there was concern that the sbc kernel will overcharge the battery and thus kill the life of the battery and or it can cause it to explode. now in the past, if you look around the net, you will see that people were concerned for their phones exploding due to the use of sbc kernels. though there were a few cases (supposedly) of exploding phones early on, there has not been any reported that i know of since. and yes sbc kernels may degrade your battery down faster then non sbc kernels. however, i think that the trade off of getting better battery life is better then having a battery last longer. batteries are cheap these days anyways.
More on Kernels
now one thing about kernels and batteries is that the results may very for most people. kernels tend to react differently on different phones. there are just too many variables to consider. the best thing to do is to make a nandroid and try the kernels out and find out what works for you on your phone. every custom rom comes with its own kernel which in most cases is just stock. in order to switch kernels, all you would have to do is just flash a custom one of your choice. just make sure that you make a nandroid backup first then wipe dalvik cache and cache and flash away.
kernels are designed to work the two main types of rom. there are one for sense and then there are ones for AOSP(Android Open Source Project). they also make universal kernels that works on both AOSP and sense. however, the AOSP kernels will not work on a sense rom and vice versa. Also the new gingerbread roms will not work with froyo kernels. the main thing is to make sure that you know what kernel you are flashing and what rom you have.
Flashing Kernels
this is how it is done:1.download the kernel of your choice
2.transfer the file over to the card
3.go into recovery
4.make a nandroid backup
5.wipe dalvik cache and cache
6.flash the zip file
7.reboot.
Setcpu
what is setcpu? it is an app found on the market that works on most android devices. its main purpose is to set and maintain cpu frequencies. also you will need a custom kernel if you want to over and underclock your phone using setcpu.
not all phones have the same threshold for overclocking so you have to be careful on how high you set the frequency. make sure that the set on boot found on the main screen is not checked. if you overclock to high then your phone will not work right. it will seize up and could cause a reboot. if you have set on boot at that level then you will get a bootloop that is hard to get out of. once you know at what point your phone is overclocked but stable, then you can go ahead and set it on boot.
as far as profiles go, i would bot recommend having too many. it is counterproductive and if you have a lot of profiles, then setcpu will then be working that much harder to monitor and maintain those profiles. usually a screen off profile is good enough to help save battery.
Governors
scaling governors control exactly how the cpu scales between your "max" and "min" set frequencies.
here is a great explanantion of some of the governors out there. thanx NaterTots!!!!!
NaterTots said:
Links
you can download setcpu from the market.
checkout this guide:setcpu guide
if you want to read more here are some threads you might want to checkout:
[GUIDE]
