Messages in this thread | | | Date | Mon, 18 Jul 2022 08:49:42 -0400 | Subject | Re: [PATCH v3 2/2] perf tsc: Add arch TSC frequency information | From | "Liang, Kan" <> |
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On 2022-07-15 6:35 p.m., Ian Rogers wrote: > From: Kan Liang <kan.liang@linux.intel.com> > > The TSC frequency information is required for the event metrics with > the literal, system_tsc_freq. For the newer Intel platform, the TSC > frequency information can be retrieved from the CPUID leaf 0x15. > If the TSC frequency information isn't present the /proc/cpuinfo > approach is used. > > Refactor cpuid for this use. Note, the previous stack pushing/popping > approach was broken on x86-64 that has stack red zones that would be > clobbered. > > Signed-off-by: Kan Liang <kan.liang@linux.intel.com> > Signed-off-by: Ian Rogers <irogers@google.com> > --- > tools/perf/arch/x86/util/cpuid.h | 34 +++++++++++++++++++++++++++++++ > tools/perf/arch/x86/util/header.c | 27 ++++++++++-------------- > tools/perf/arch/x86/util/tsc.c | 33 ++++++++++++++++++++++++++++++ > tools/perf/util/expr.c | 15 +++++++++++++- > tools/perf/util/tsc.h | 1 + > 5 files changed, 93 insertions(+), 17 deletions(-) > create mode 100644 tools/perf/arch/x86/util/cpuid.h > > diff --git a/tools/perf/arch/x86/util/cpuid.h b/tools/perf/arch/x86/util/cpuid.h > new file mode 100644 > index 000000000000..0a3ae0ace7e9 > --- /dev/null > +++ b/tools/perf/arch/x86/util/cpuid.h > @@ -0,0 +1,34 @@ > +/* SPDX-License-Identifier: GPL-2.0 */ > +#ifndef PERF_CPUID_H > +#define PERF_CPUID_H 1 > + > + > +static inline void > +cpuid(unsigned int op, unsigned int op2, unsigned int *a, unsigned int *b, > + unsigned int *c, unsigned int *d) > +{ > + /* > + * Preserve %ebx/%rbx register by either placing it in %rdi or saving it > + * on the stack - x86-64 needs to avoid the stack red zone. In PIC > + * compilations %ebx contains the address of the global offset > + * table. %rbx is occasionally used to address stack variables in > + * presence of dynamic allocas. > + */ > + asm( > +#if defined(__x86_64__) > + "mov %%rbx, %%rdi\n" > + "cpuid\n" > + "xchg %%rdi, %%rbx\n" > +#else > + "pushl %%ebx\n" > + "cpuid\n" > + "movl %%ebx, %%edi\n" > + "popl %%ebx\n" > +#endif > + : "=a"(*a), "=D"(*b), "=c"(*c), "=d"(*d) > + : "a"(op), "2"(op2)); > +} > + > +void get_cpuid_0(char *vendor, unsigned int *lvl); > + > +#endif > diff --git a/tools/perf/arch/x86/util/header.c b/tools/perf/arch/x86/util/header.c > index 578c8c568ffd..a51444a77a5f 100644 > --- a/tools/perf/arch/x86/util/header.c > +++ b/tools/perf/arch/x86/util/header.c > @@ -9,18 +9,17 @@ > > #include "../../../util/debug.h" > #include "../../../util/header.h" > +#include "cpuid.h" > > -static inline void > -cpuid(unsigned int op, unsigned int *a, unsigned int *b, unsigned int *c, > - unsigned int *d) > +void get_cpuid_0(char *vendor, unsigned int *lvl) > { > - __asm__ __volatile__ (".byte 0x53\n\tcpuid\n\t" > - "movl %%ebx, %%esi\n\t.byte 0x5b" > - : "=a" (*a), > - "=S" (*b), > - "=c" (*c), > - "=d" (*d) > - : "a" (op)); > + unsigned int b, c, d; > + > + cpuid(0, 0, lvl, &b, &c, &d); > + strncpy(&vendor[0], (char *)(&b), 4); > + strncpy(&vendor[4], (char *)(&d), 4); > + strncpy(&vendor[8], (char *)(&c), 4); > + vendor[12] = '\0'; > } > > static int > @@ -31,14 +30,10 @@ __get_cpuid(char *buffer, size_t sz, const char *fmt) > int nb; > char vendor[16]; > > - cpuid(0, &lvl, &b, &c, &d); > - strncpy(&vendor[0], (char *)(&b), 4); > - strncpy(&vendor[4], (char *)(&d), 4); > - strncpy(&vendor[8], (char *)(&c), 4); > - vendor[12] = '\0'; > + get_cpuid_0(vendor, &lvl); > > if (lvl >= 1) { > - cpuid(1, &a, &b, &c, &d); > + cpuid(1, 0, &a, &b, &c, &d); > > family = (a >> 8) & 0xf; /* bits 11 - 8 */ > model = (a >> 4) & 0xf; /* Bits 7 - 4 */ > diff --git a/tools/perf/arch/x86/util/tsc.c b/tools/perf/arch/x86/util/tsc.c > index 559365f8fe52..b69144f22489 100644 > --- a/tools/perf/arch/x86/util/tsc.c > +++ b/tools/perf/arch/x86/util/tsc.c > @@ -1,7 +1,9 @@ > // SPDX-License-Identifier: GPL-2.0 > #include <linux/types.h> > +#include <string.h> > > #include "../../../util/tsc.h" > +#include "cpuid.h" > > u64 rdtsc(void) > { > @@ -11,3 +13,34 @@ u64 rdtsc(void) > > return low | ((u64)high) << 32; > } > + > +double arch_get_tsc_freq(void) > +{ > + unsigned int a, b, c, d, lvl; > + static bool cached; > + static double tsc; > + char vendor[16]; > + > + if (cached) > + return tsc; > + > + cached = true; > + get_cpuid_0(vendor, &lvl); > + if (!strstr(vendor, "Intel")) > + return 0; > + > + /* > + * Don't support Time Stamp Counter and > + * Nominal Core Crystal Clock Information Leaf. > + */ > + if (lvl < 0x15) > + return 0; > + > + cpuid(0x15, 0, &a, &b, &c, &d); > + /* TSC frequency is not enumerated */ > + if (!a || !b || !c) > + return 0; > + > + tsc = (double)c * (double)b / (double)a; > + return tsc; > +} > diff --git a/tools/perf/util/expr.c b/tools/perf/util/expr.c > index 4c81533e4b43..16f10e6d5ca5 100644 > --- a/tools/perf/util/expr.c > +++ b/tools/perf/util/expr.c > @@ -12,6 +12,7 @@ > #include "expr-bison.h" > #include "expr-flex.h" > #include "smt.h" > +#include "tsc.h" > #include <linux/err.h> > #include <linux/kernel.h> > #include <linux/zalloc.h> > @@ -443,9 +444,19 @@ static double system_tsc_freq(void) > > free(line); > fclose(cpuinfo); > + if (isnan(result)) > + pr_err("Error reading system_tsc_freq"); > + > return result; > } > > +#if !defined(__i386__) && !defined(__x86_64__) > +double arch_get_tsc_freq(void)
Other arch_* functions are __weak functions. I think it's better to keep it consistent. It also avoid to add a new #if defined when adding a new arch. Is there a problem to use __weak here?
Thanks, Kan
> +{ > + return 0.0; > +} > +#endif > + > double expr__get_literal(const char *literal) > { > static struct cpu_topology *topology; > @@ -462,7 +473,9 @@ double expr__get_literal(const char *literal) > } > > if (!strcasecmp("#system_tsc_freq", literal)) { > - result = system_tsc_freq(); > + result = arch_get_tsc_freq(); > + if (fpclassify(result) == FP_ZERO) > + result = system_tsc_freq(); > goto out; > } > > diff --git a/tools/perf/util/tsc.h b/tools/perf/util/tsc.h > index 7d83a31732a7..88fd1c4c1cb8 100644 > --- a/tools/perf/util/tsc.h > +++ b/tools/perf/util/tsc.h > @@ -25,6 +25,7 @@ int perf_read_tsc_conversion(const struct perf_event_mmap_page *pc, > u64 perf_time_to_tsc(u64 ns, struct perf_tsc_conversion *tc); > u64 tsc_to_perf_time(u64 cyc, struct perf_tsc_conversion *tc); > u64 rdtsc(void); > +double arch_get_tsc_freq(void); > > size_t perf_event__fprintf_time_conv(union perf_event *event, FILE *fp); >
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