Messages in this thread Patch in this message | | | Date | Wed, 14 Jul 2021 10:59:49 -0300 | From | Arnaldo Carvalho de Melo <> | Subject | Re: [PATCH v4 10/11] perf env: Set flag for kernel is 64-bit mode |
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Em Tue, Jul 13, 2021 at 05:31:03PM +0000, Hunter, Adrian escreveu: > > On Mon, Jul 12, 2021 at 03:14:35PM -0300, Arnaldo Carvalho de Melo wrote: > > > Em Sun, Jul 11, 2021 at 06:41:04PM +0800, Leo Yan escreveu: > > > > +++ b/tools/perf/util/env.c > > > > @@ -11,6 +11,7 @@ > > > > #include <stdlib.h> > > > > #include <string.h>
> > > > +int kernel_is_64_bit; > > > > struct perf_env perf_env;
> > > Why can't this be in 'struct perf_env'?
> > Good question. I considered to add it in struct perf_env but finally I used this > > way; the reason is this variable "kernel_is_64_bit" is only used during > > recording phase for AUX ring buffer, and don't use it for report. So seems to > > me it's over complexity to add a new field and just wander if it's necessary to > > save this field as new feature in the perf header.
> I think we store the arch, so if the "kernel_is_64_bit" calculation depends only on arch > then I guess we don't need a new feature at the moment.
So, I wasn't suggesting to add this info to the perf.data file header, just to the in-memory 'struct perf_env'.
And also we should avoid unconditionally initializing things that we may never need, please structure it as: static void perf_env__init_kernel_mode(struct perf_env *env) { const char *arch = perf_env__raw_arch(env); if (!strncmp(arch, "x86_64", 6) || !strncmp(arch, "aarch64", 7) || !strncmp(arch, "arm64", 5) || !strncmp(arch, "mips64", 6) || !strncmp(arch, "parisc64", 8) || !strncmp(arch, "riscv64", 7) || !strncmp(arch, "s390x", 5) || !strncmp(arch, "sparc64", 7)) kernel_is_64_bit = 1; else kernel_is_64_bit = 0; }
void perf_env__init(struct perf_env *env) { ... env->kernel_is_64_bit = -1; ... } bool perf_env__kernel_is_64_bit(struct perf_env *env) { if (env->kernel_is_64_bit == -1) perf_env__init_kernel_mode(env); return env->kernel_is_64_bit; } One thing in my TODO is to crack down on the tons of initializations perf does unconditionally, last time I looked there are lots :-\
- Arnaldo
> > Combining the comment from Adrian in another email, I think it's good to add > > a new field "compat_mode" in the struct perf_env, and this field will be > > initialized in build-record.c. Currently we don't need to save this value into > > the perf file, if later we need to use this value for decoding phase, then we > > can add a new feature item to save "compat_mode" > > into the perf file's header.
> > If you have any different idea, please let me know. Thanks!
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