From: Peter Zijlstra <peterz@infradead.org>
To: Dave Hansen <dave.hansen@intel.com>
Cc: "Liang, Kan" <kan.liang@linux.intel.com>,
Stephane Eranian <eranian@google.com>,
Ingo Molnar <mingo@redhat.com>,
Arnaldo Carvalho de Melo <acme@kernel.org>,
LKML <linux-kernel@vger.kernel.org>,
Mark Rutland <mark.rutland@arm.com>,
Alexander Shishkin <alexander.shishkin@linux.intel.com>,
Jiri Olsa <jolsa@redhat.com>, Andi Kleen <ak@linux.intel.com>,
kirill.shutemov@linux.intel.com,
Michael Ellerman <mpe@ellerman.id.au>,
benh@kernel.crashing.org, Paul Mackerras <paulus@samba.org>,
Andy Lutomirski <luto@amacapital.net>
Subject: Re: [PATCH V8 1/4] perf/core: Add PERF_SAMPLE_DATA_PAGE_SIZE
Date: Thu, 1 Oct 2020 16:23:08 +0200 [thread overview]
Message-ID: <20201001142308.GR2628@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <641fa138-23b7-8fdd-27f9-87e2fdd9fa91@intel.com>
On Thu, Oct 01, 2020 at 06:49:36AM -0700, Dave Hansen wrote:
> On 9/30/20 10:30 AM, Peter Zijlstra wrote:
> > In general though; I think using ->active_mm is a mistake though. That
> > code should be doing something like:
> >
> >
> > mm = current->mm;
> > if (!mm)
> > mm = &init_mm;
> >
>
> I was hoping that using ->active_mm would give us the *actual* copy of
> the page tables that's loaded in CR3 for kernel thraeds. But, there are
> few if any practical advantages of doing that at the moment.
Some of us hate active_mm with a passion and want to remove it entirely
(/me waves at amluto).
Also, if !current->mm, it had better not be accessing anything outside
of the kernel map, so &init_mm should cover that just fine. And given
the kernel maps are shared between all CR3s, they'll see the exact same
pagetables.
next prev parent reply other threads:[~2020-10-01 14:23 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-21 15:26 [PATCH V8 0/4] Add the page size in the perf record (kernel) kan.liang
2020-09-21 15:26 ` [PATCH V8 1/4] perf/core: Add PERF_SAMPLE_DATA_PAGE_SIZE kan.liang
2020-09-30 7:15 ` Stephane Eranian
2020-09-30 13:51 ` Dave Hansen
2020-09-30 14:42 ` Liang, Kan
2020-09-30 14:48 ` Dave Hansen
2020-09-30 17:17 ` Stephane Eranian
2020-09-30 17:30 ` Peter Zijlstra
2020-09-30 22:45 ` Stephane Eranian
2020-10-01 13:30 ` Liang, Kan
2020-10-01 13:49 ` Dave Hansen
2020-10-01 14:23 ` Peter Zijlstra [this message]
2020-09-21 15:26 ` [PATCH V8 2/4] perf/x86/intel: Support PERF_SAMPLE_DATA_PAGE_SIZE kan.liang
2020-09-21 15:26 ` [PATCH V8 3/4] powerpc/perf: " kan.liang
2020-09-21 15:26 ` [PATCH V8 4/4] perf/core: Add support for PERF_SAMPLE_CODE_PAGE_SIZE kan.liang
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