On Mon, Nov 17, 2008 at 11:18 PM, Linus Torvalds <[EMAIL PROTECTED]> wrote: > I do wonder just _what_ it is that causes the stack frames to be so > horrid. For example, you have > > 18) 8896 160 .kmem_cache_alloc+0xfc/0x140 > > and I'm looking at my x86-64 compile, and it has a stack frame of just 8 > bytes (!) for local variables plus the save/restore area (which looks like > three registers plus frame pointer plus return address). IOW, if I'm > looking at the code right (so big caveat: I did _not_ do a real stack > dump!) the x86-64 stack cost for that same function is on the order of 48 > bytes. Not 160. > > Where does that factor-of-three+ difference come from? From the numbers, I > suspect ppc64 has a 32-byte stack alignment, which may be part of it, and > I guess the compiler is more eager to use all those extra registers and > will happily have many more callee-saved regs that are actually used. > > But that still a _lot_ of extra stack. > > Of course, you may have things like spinlock debugging etc enabled. Some > of our debugging options do tend to blow things up.
Note that kmem_cache_alloc() is likely to contain lots of inlined functions for both SLAB and SLUB. Perhaps that blows up stack usage on ppc? _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@ozlabs.org https://ozlabs.org/mailman/listinfo/linuxppc-dev
