From: Ard Biesheuvel <ardb@kernel.org>
To: linux-arm-kernel@lists.infradead.org
Cc: Ard Biesheuvel <ardb@kernel.org>,
Linus Walleij <linus.walleij@linaro.org>,
Arnd Bergmann <arnd@arndb.de>,
Russell King <linux@armlinux.org.uk>,
Nicolas Pitre <nico@fluxnic.net>
Subject: [PATCH v2 1/8] ARM: vfp: Record VFP bounces as perf emulation faults
Date: Wed, 17 May 2023 23:28:01 +0200 [thread overview]
Message-ID: <20230517212808.3895190-2-ardb@kernel.org> (raw)
In-Reply-To: <20230517212808.3895190-1-ardb@kernel.org>
VFP 'bouncing' occurs when the VFP unit cannot complete the execution of
a VFP instruction, either because it is not implemented at all, or
because the values of the arguments are out of range for the hardware
implementation, and the software needs to step in to complete the
operation.
To give some insight in how much certain programs rely on this bouncing,
record the emulation of a VFP instruction in perf's emulation-faults
counter.
This can be used like so
perf stat -e emulation-faults ./testfloat -all2
and the output will be something like
Performance counter stats for './testfloat -all2':
259,277 emulation-faults:u
6.846432176 seconds time elapsed
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
---
arch/arm/vfp/vfpmodule.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/arch/arm/vfp/vfpmodule.c b/arch/arm/vfp/vfpmodule.c
index 349dcb944a937a72..08d5dfcf70796eea 100644
--- a/arch/arm/vfp/vfpmodule.c
+++ b/arch/arm/vfp/vfpmodule.c
@@ -18,6 +18,7 @@
#include <linux/uaccess.h>
#include <linux/user.h>
#include <linux/export.h>
+#include <linux/perf_event.h>
#include <asm/cp15.h>
#include <asm/cputype.h>
@@ -313,6 +314,7 @@ static u32 vfp_emulate_instruction(u32 inst, u32 fpscr, struct pt_regs *regs)
* emulate it.
*/
}
+ perf_sw_event(PERF_COUNT_SW_EMULATION_FAULTS, 1, regs, regs->ARM_pc);
return exceptions & ~VFP_NAN_FLAG;
}
--
2.39.2
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next prev parent reply other threads:[~2023-05-17 21:28 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-05-17 21:28 [PATCH v2 0/8] ARM: vfp: Reimplement dispatch and support logic in C Ard Biesheuvel
2023-05-17 21:28 ` Ard Biesheuvel [this message]
2023-05-17 21:28 ` [PATCH v2 2/8] ARM: vfp: Remove workaround for Feroceon CPUs Ard Biesheuvel
2023-05-17 21:28 ` [PATCH v2 3/8] ARM: vfp: Reimplement VFP exception entry in C code Ard Biesheuvel
2023-05-17 21:28 ` [PATCH v2 4/8] ARM: kernel: Get rid of thread_info::used_cp[] array Ard Biesheuvel
2023-05-17 21:28 ` [PATCH v2 5/8] ARM: vfp: Use undef hook for handling VFP exceptions Ard Biesheuvel
2023-05-17 21:28 ` [PATCH v2 6/8] ARM: entry: Disregard Thumb undef exception in coproc dispatch Ard Biesheuvel
2023-05-17 21:28 ` [PATCH v2 7/8] ARM: iwmmxt: Use undef hook to enable coprocessor for task Ard Biesheuvel
2023-05-17 21:28 ` [PATCH v2 8/8] ARM: entry: Make asm coproc dispatch code NWFPE only Ard Biesheuvel
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