Re: [PATCH] reduce large do_mount stack usage with noinlines

Eric Sandeen
2008-02-07T23:09:07Z

Andrew Morton wrote:
> On Wed, 06 Feb 2008 17:11:38 -0600
> Eric Sandeen <sandeen@redhat.com> wrote:
>
>> /*
>> * recursively change the type of the mountpoint.
>> + * noinline this do_mount helper to save do_mount stack space.
>> */
>> -static int do_change_type(struct nameidata *nd, int flag)
>> +static noinline int do_change_type(struct nameidata *nd, int flag)
>
> What we could do here is defined a new noinline_because_of_stack_suckiness
> and use that.

Something like:

Index: linux-2.6.24-mm1/include/linux/compiler-gcc.h
===================================================================
--- linux-2.6.24-mm1.orig/include/linux/compiler-gcc.h
+++ linux-2.6.24-mm1/include/linux/compiler-gcc.h
@@ -53,3 +53,9 @@
#define noinline __attribute__((noinline))
#define __attribute_const__ __attribute__((__const__))
#define __maybe_unused __attribute__((unused))
+
+/*
+ * When gcc inlines multiple functions into a parent function,
+ * the stack space used sometimes increases excessively...
+ */
+#define noinline_stackspace noinline

?

I couldn't think of a great name for it. There are several noinline
users throughout the kernel with stackspace related comments, so if
desired, I could sprinkle this around. I'm not very pleased with it
aesthetically though. :)

-Eric