On Tue, 3 Nov 2015, Arnd Bergmann wrote: > On Tuesday 03 November 2015 13:32:17 kbuild test robot wrote: > > > > net/can/bcm.c: In function 'bcm_proc_show': > > >> net/can/bcm.c:223:1: warning: the frame size of 1156 bytes is larger than 1024 bytes [-Wframe-larger-than=] > > } > > Interesting, that is a lot of stack for a function that only has a couple > of local variables: > > #define IFNAMSIZ 16 > char ifname[IFNAMSIZ]; > struct sock *sk = (struct sock *)m->private; > struct bcm_sock *bo = bcm_sk(sk); > struct bcm_op *op; > > > This is a parisc-allyesconfig kernel, so I assume that CONFIG_PROFILE_ALL_BRANCHES > is on, which instruments every 'if' in the kernel. If that causes problems, > we could decide to disable the do_div optimization whenever CONFIG_PROFILE_ALL_BRANCHES > is enabled. I have an ARM allyesconfig build here where that function needs a frame of 88 bytes only. And that is with my do_div optimization applied. With the do_div optimization turned off, the stack frame is still 88 bytes. Turning on CONFIG_PROFILE_ALL_BRANCHES makes the frame size to grow to 96 bytes. Keeping CONFIG_PROFILE_ALL_BRANCHES=y and activating the do_div optimization again, and the function frame size goes back to 88 bytes. So I wonder what parisc gcc could be doing with this code. Nicolas -- To unsubscribe from this list: send the line "unsubscribe linux-arch" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
