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SubjectRe: [PATCH 1/2] perf kmem: Support legacy tracepoints
Em Mon, Jan 09, 2023 at 03:11:47PM +0000, James Clark escreveu:
>
>
> On 08/01/2023 06:23, Leo Yan wrote:
> > Commit 11e9734bcb6a ("mm/slab_common: unify NUMA and UMA version of
> > tracepoints") removed tracepoints 'kmalloc_node' and
> > 'kmem_cache_alloc_node', these two tracepoints have disappeared in the
> > latest kernel, but we also need to consider the tool should be backward
> > compatible with old kernels.
> >
> > If detects the tracepoint "kmem:kmalloc_node" is existed on a system,
> > this patch enables the legacy tracepoints, otherwise, it will ignore
> > them for the new kernels.
> >
> > Reported-by: Ravi Bangoria <ravi.bangoria@amd.com>
> > Fixes: 11e9734bcb6a ("mm/slab_common: unify NUMA and UMA version of tracepoints")
> > Signed-off-by: Leo Yan <leo.yan@linaro.org>
> > ---
> > tools/perf/builtin-kmem.c | 29 ++++++++++++++++++++++++++---
> > 1 file changed, 26 insertions(+), 3 deletions(-)
> >
> > diff --git a/tools/perf/builtin-kmem.c b/tools/perf/builtin-kmem.c
> > index e20656c431a4..50a3df5dc18a 100644
> > --- a/tools/perf/builtin-kmem.c
> > +++ b/tools/perf/builtin-kmem.c
> > @@ -1824,6 +1824,19 @@ static int parse_line_opt(const struct option *opt __maybe_unused,
> > return 0;
> > }
> >
> > +static bool slab_legacy_tp_is_exposed(void)
> > +{
> > + /*
> > + * The tracepoints "kmem:kmalloc_node" and
> > + * "kmem:kmem_cache_alloc_node" have been removed on the latest
> > + * kernel, if the tracepoint "kmem:kmalloc_node" is existed it
> > + * means the tool is running on an old kernel, we need to
> > + * rollback to support these legacy tracepoints.
> > + */
> > + return IS_ERR(trace_event__tp_format("kmem", "kmalloc_node")) ?
> > + false : true;
> > +}
> > +
> > static int __cmd_record(int argc, const char **argv)
> > {
> > const char * const record_args[] = {
> > @@ -1831,22 +1844,28 @@ static int __cmd_record(int argc, const char **argv)
> > };
> > const char * const slab_events[] = {
> > "-e", "kmem:kmalloc",
> > - "-e", "kmem:kmalloc_node",
> > "-e", "kmem:kfree",
> > "-e", "kmem:kmem_cache_alloc",
> > - "-e", "kmem:kmem_cache_alloc_node",
> > "-e", "kmem:kmem_cache_free",
> > };
> > + const char * const slab_legacy_events[] = {
> > + "-e", "kmem:kmalloc_node",
> > + "-e", "kmem:kmem_cache_alloc_node",
> > + };
>
> Reviewed-by: James Clark <james.clark@arm.com>
>
> This fixes the error with mem:kmalloc_node for me.
>
> I was thinking that it might be best to add all events to the list
> conditionally instead of just the legacy ones. That way, the same error
> won't happen in the future. But maybe it's best to have an explicit
> error again in case the breaking change was unintentional so it's fine
> as it is I think.

Just applied this, the changes you brains stormed may come as later
patches, thanks,

- Arnaldo

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