>> > >> > Yes, this prevents adding more pcpu chunks and so cause "atomic" >> > allocations >> > to fail more easily. >> >> Then I fail to see what is the problem you are trying to fix. > > To be more specific. Could you describe what more can we do in the > vmalloc layer for GFP_NOWAIT allocations? They certainly cannot sleep > and cannot perform the reclaim so you have to rely on the background > work.
The main problem that I am trying to fix is in percpu.c code. It currently doesn't even attempt to call vmalloc() for GFP_NOWAIT case. It solely relies on the background allocator to replenish the reserves. I would like percpu.c to call __vmalloc(GFP_NOWAIT) inline and see whether that succeeds. If that fails, it is fair to fail the call. For this to work, __vmalloc() should be ready to serve a caller that is holding a spinlock. The might_sleep() in alloc_vmap_area() basically prevents us calling vmalloc in this context.
