On Thu, Feb 04, 2021 at 04:24:20PM -0800, John Hubbard wrote: > On 2/4/21 4:12 PM, Minchan Kim wrote: > ... > > > > Then, how to know how often CMA API failed? > > > > > > Why would you even need to know that, *in addition* to knowing specific > > > page allocation numbers that failed? Again, there is no real-world motivation > > > cited yet, just "this is good data". Need more stories and support here. > > > > Let me give an example. > > > > Let' assume we use memory buffer allocation via CMA for bluetooth > > enable of device. > > If user clicks the bluetooth button in the phone but fail to allocate > > the memory from CMA, user will still see bluetooth button gray. > > User would think his touch was not enough powerful so he try clicking > > again and fortunately CMA allocation was successful this time and > > they will see bluetooh button enabled and could listen the music. > > > > Here, product team needs to monitor how often CMA alloc failed so > > if the failure ratio is steadily increased than the bar, > > it means engineers need to go investigation. > > > > Make sense? > > > > Yes, except that it raises more questions: > > 1) Isn't this just standard allocation failure? Don't you already have a way > to track that? > > Presumably, having the source code, you can easily deduce that a bluetooth > allocation failure goes directly to a CMA allocation failure, right? > > Anyway, even though the above is still a little murky, I expect you're right > that it's good to have *some* indication, somewhere about CMA behavior... > > Thinking about this some more, I wonder if this is really /proc/vmstat sort > of data that we're talking about. It seems to fit right in there, yes? Thing is CMA instance are multiple, cma-A, cma-B, cma-C and each of CMA heap has own specific scenario. /proc/vmstat could be bloated a lot while CMA instance will be increased.
