Messages in this thread | | | Subject | Re: [RFC][PATCH 7/7] perf: Optimize sw events | From | Peter Zijlstra <> | Date | Fri, 15 Oct 2010 11:14:03 +0200 |
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On Thu, 2010-10-14 at 22:34 +0200, Peter Zijlstra wrote:
> Index: linux-2.6/include/linux/perf_event.h > =================================================================== > --- linux-2.6.orig/include/linux/perf_event.h > +++ linux-2.6/include/linux/perf_event.h > @@ -1013,15 +1013,17 @@ static inline void perf_fetch_caller_reg > static inline void > perf_sw_event(u32 event_id, u64 nr, int nmi, struct pt_regs *regs, u64 addr) > { > - if (atomic_read(&perf_swevent_enabled[event_id])) { > - struct pt_regs hot_regs; > + struct pt_regs hot_regs; > > - if (!regs) { > - perf_fetch_caller_regs(&hot_regs); > - regs = &hot_regs; > - } > - __perf_sw_event(event_id, nr, nmi, regs, addr); > + JUMP_LABEL(&perf_swevent_enabled[event_id], have_event); > + return; > + > +have_event: > + if (!regs) { > + perf_fetch_caller_regs(&hot_regs); > + regs = &hot_regs; > } > + __perf_sw_event(event_id, nr, nmi, regs, addr); > } >
OK, so it appears I only compile tested this bit without jump_label support, with that bit added back this horribly fails to compile like:
In file included from /usr/src/linux-2.6/arch/x86/mm/fault.c:13: /usr/src/linux-2.6/include/linux/perf_event.h: In function ‘perf_sw_event.clone.0’: /usr/src/linux-2.6/include/linux/perf_event.h:1018: warning: asm operand 0 probably doesn’t match constraints /usr/src/linux-2.6/include/linux/perf_event.h:1018: error: impossible constraint in ‘asm’
The relevant snippet from the .i file reads:
static inline void perf_sw_event(u32 event_id, u64 nr, int nmi, struct pt_regs *regs, u64 addr) { struct pt_regs hot_regs;
do { asm goto("1:" ".byte 0xe9 \n\t .long 0\n\t" ".pushsection __jump_table, \"a\" \n\t" " " ".quad" " " "1b, %l[" "have_event" "], %c0 \n\t" ".popsection \n\t" : : "i" (&perf_swevent_enabled[event_id]) : : have_event); } while (0); return;
have_event: if (!regs) { perf_fetch_caller_regs(&hot_regs); regs = &hot_regs; } __perf_sw_event(event_id, nr, nmi, regs, addr); }
Anybody got any clue as to why this goes splat?
I tried both:
gcc (GCC) 4.4.4 20100630 (Red Hat 4.4.4-10)
and
x86_64-linux-gcc (GCC) 4.5.1
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