On Mon, Mar 16, 2015 at 07:06:55PM +0300, Stefan Strogin wrote: > Hi all. > > Here is the fourth version of a patch set that adds some debugging facility for > CMA. > > This patch set is based on next-20150316. > It is also available on git: > git://github.com/stefanstrogin/linux -b cmainfo-v4 > > We want an interface to see a list of currently allocated CMA buffers and some > useful information about them (like /proc/vmallocinfo but for physically > contiguous buffers allocated with CMA). > > For example. We want a big (megabytes) CMA buffer to be allocated in runtime > in default CMA region. If someone already uses CMA then the big allocation > could fail. If it happened then with such an interface we could find who used > CMA at the moment of failure, who caused fragmentation and so on. Ftrace also > would be helpful here, but with ftrace we can see the whole history of > allocations and releases, whereas with this patch set we can see a snapshot of > CMA region with actual information about its allocations. Hello, Hmm... I still don't think that this is really helpful to find root cause of fragmentation. Think about following example. Assume 1024 MB CMA region. 128 MB allocation * 4 1 MB allocation 128 MB allocation 128 MB release * 4 (first 4) try 512 MB allocation With above sequences, fragmentation happens and 512 MB allocation would be failed. We can get information about 1 MB allocation and 128 MB one from the buffer list as you suggested, but, fragmentation are related to whole sequence of allocation/free history, not snapshot of allocation. Thanks. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>