Andrew Morton wrote: > Does the patch actually help? I mean, if a() calls b() and both use N > bytes of locals, our worst-case stack usage remains ~2N whether or not b() > was inlined in a()? In fact, uninlining makes things a little worse due to > callframe stuff.
I think it does. [linux-2.6.24-mm1]$ make fs/namespace.o > /dev/null [linux-2.6.24-mm1]$ objdump -d fs/namespace.o | scripts/checkstack.pl x86_64 | grep do_mount 0x00002307 do_mount [namespace.o]: 616 [linux-2.6.24-mm1]$ quilt push Applying patch patches/do_mount_stack patching file fs/namespace.c Now at patch patches/do_mount_stack [linux-2.6.24-mm1]$ make fs/namespace.o > /dev/null [linux-2.6.24-mm1]$ objdump -d fs/namespace.o | scripts/checkstack.pl x86_64 | grep do_mount 0x00002a8b do_mount [namespace.o]: 168 So clearly that one function is reduced. But it's more than that.... I guess the problem is a() calls b() or c() or d() or e() or f(), and gcc adds up all that stack usage, or seems to, and we get more like 6N regardless of the path taken. For example, 2 of the helper functions, once un-inlined, are: 0x00001fd9 do_move_mount [namespace.o]: 288 0x00001e94 do_loopback [namespace.o]: 168 so it looks like we do carry that baggage even if we go the do_new_mount() path for example. >> -static int do_change_type(struct nameidata *nd, int flag) >> +static noinline int do_change_type(struct nameidata *nd, int flag) > > There's no way for the reader to work out why this is here, so I do think > it should be commented somewhere. Ok, good point, will resend... want a comment on each, or perhaps above do_mount? I suppose on each. -Eric -- 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/
