动态内存分配/利用未使用的内存

Question

I'm going to write an application that needs a lot of memory dynamically. Most of the memory is used for caching purposes and is just used for speed ups. Those parts could actually be freed on demand.

Unfortunately my kernel will kill the process if it runs out of memory. But it could simply free memory. So what I want is very similar to the linux page cache as it is explained here . Is it possible to implement such behaviour in userspace in a convenient way?

I'm thinking about implementing such a cache with "cache files" which are stored on a ramfs/tmpfs with memory mapped file IO, but i'm sure, that there is a more comfortable way.

Thanks in advance!

Answer 1

Yes this should be possible. Most kernels have a memory alloc method where the process sleeps until it gets the requested memory. ( all the kernels ive worked with have). If yours doesnt this may be a good time to implement one. You could check out the kmem functions in linux. However this is a passive way of doing what youve asked. The process will be waiting until someone else frees up memory. If you want to free up memory from your own process address space when theres no memory, this can be done easily from user space. You need to keep a journal of allocated memory and free the ones you dont need on demand when an alloc fails.