On 10/20/21 13:46, Hyeonggon Yoo wrote: > On Sun, Oct 17, 2021 at 08:38:41PM -0700, Rustam Kovhaev wrote: >> Let's prepend all allocations of (PAGE_SIZE - align_offset) and less >> with the size header. This way kmem_cache_alloc() memory can be freed >> with kfree() and the other way around, as long as they are less than >> (PAGE_SIZE - align_offset). > > Hello Rustam, I measured its impact on memory usage on > tiny kernel configuration as SLOB is used in very small machine. > > on x86 32 bit + tinyconfig: > Before: > Slab: 668 kB > > After: > Slab: 688~692 kB > > it adds 20~24kB. Thanks for the measurement. That's 3.5% increase. > >> >> The main reason for this change is to simplify SLOB a little bit, make >> it a bit easier to debug whenever something goes wrong. >> > > It seems acceptable But I wonder it is worth to increase memory usage > to allow freeing kmem_cache_alloc-ed objects by kfree()? Not for the reason above, but for providing a useful API guarantee regardless of selected slab allocator IMHO yes. > Thanks, > Hyeonggon > >> meminfo right after the system boot, without the patch: >> Slab: 35500 kB >> >> the same, with the patch: >> Slab: 36396 kB >> >
