On Thu, Jul 16, 2015 at 3:42 PM, H. Peter Anvin <[email protected]> wrote: > On 07/16/2015 12:14 PM, Dave Hansen wrote: >> The FPU rewrite removed the dynamic allocations of 'struct fpu'. >> But, this potentially wastes massive amounts of memory (2k per >> task on systems that do not have AVX-512 for instance). >> >> Instead of having a separate slab, this patch just appends the >> space that we need to the 'task_struct' which we dynamically >> allocate already. This saves from doing an extra slab allocation >> at fork(). The only real downside here is that we have to stick >> everything and the end of the task_struct. But, I think the >> BUILD_BUG_ON()s I stuck in there should keep that from being too >> fragile. >> >> This survives a quick build and boot in a VM. Does anyone see any >> real downsides to this? >> > > No. I have also long advocated for merging task_struct and thread_info > into a common structure and get it off the stack; it would improve > security and avoid weird corner cases in the irqstack handling. >
In tip/x86/asm, entry_64.S only references thread_info in two places, both in the syscall code. I'm hoping that we can move that code into C soon and that we can do the same thing to the 32-bit code. If we do that, then we could just move ti->flags into thread_struct. Everything else should be easy, and then thread_info would be empty. --Andy -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
