On Thu, Apr 15, 2010 at 11:26 AM, Vikash Kumar <vikashskumar@xxxxxxxxx> wrote: > On Wed, Apr 14, 2010 at 9:09 PM, Manish Regmi <regmi.manish@xxxxxxxxx> wrote: >> On Wed, Apr 14, 2010 at 10:18 AM, Manish Katiyar <mkatiyar@xxxxxxxxx> wrote: >>> On Wed, Apr 14, 2010 at 8:04 PM, Vikash Kumar <vikashskumar@xxxxxxxxx> wrote: >>>> Hi everyone, >>>> >>>> I am writing a simple memory manager for my application which will >>>> free any excess memory being used by my modules, so that it's >>>> available again for use. My modules allocate memory using alloc_page & >>>> kmem_cache_alloc and so the memory manager uses put_page & >>>> kmem_cache_free respectively to free up the memory which is not in >>>> use. >>>> >>>> The problem I am facing is, even after I free the memory using >>>> put_page & kmem_cache_free, my modules are not able to get the free >>>> memory. I have written a test code which allocates a lot of memory in >>>> loop and when out of memory sleeps on memory manager to free up the >>>> memory. Memory manager successfully executes free code and wakes up >>>> the sleeping process as memory should be available now. Interestingly >>>> the alloc_page / kmem_cache_alloc calls still fail to allocate >>>> memory. Now, I am clueless why it is happening so seeking help. >>> >>> Random guess... Are you sure it is still free between your free and >>> allocate. ie.. no one else comes in between takes away your memory ? > > Yes I am sure that no one else comes in to take away the freed memory. > As it is a closed system and only consumers of memory present in the > system are my modules, which are executing in a controlled environment > for testing purpose. > >>> >>> Thanks - >>> Manish >>> >>> >> >> Slab allocator does not just free the pages when u call >> kmem_cache_free. It has a list of empty, partial and full slabs. So if >> yo free it will just be in free list. have you called >> kmem_cache_destroy to destroy the whole cache? >> correct me if i am wrong here. >> > > Well it's not just the slab allocator. The main memory is consumed > using alloc_page and I keep invoking alloc_page until it fails. Slab > allocator is only used to allocate data structure to serve as the > container for these memory pages. When alloc_page fails I start > freeing up memory using put_page. But even after freeing thousands of > pages, any call to alloc_page still fails and that is the main > problem. > > As far as slab allocator is concerned. I don't want to actually > destroy them as I will need to allocate memory using them again. I was > under impression that if system is low on memory then linux memory > manager will trim the slab caches to make some memory available > anyway. Now I am not at all sure how linux memory management is > working as I don't seem to get any free memory at all. > > >> >> --------------------------------------------------------------- >> regards >> Manish Regmi >> >> http://manish-cs.blogspot.com >> http://ext2read.sf.net >> > > Regards, > Vikash Kumar > http://VikashKumar.com > I figured out the problem, it was with the API I was using. If I use __free_page instead of put_page to free the memory pages, everything works absolutely fine. That brings another question on when and why "put_page" is used. I can guess it has some thing to do with swap memory as it is defined in mm/swap.c and my system is an embedded system without any swap memory support. Thanks everyone. Regards, Vikash -- To unsubscribe from this list: send an email with "unsubscribe kernelnewbies" to ecartis@xxxxxxxxxxxx Please read the FAQ at http://kernelnewbies.org/FAQ
