From: Linus Torvalds <torvalds@linux-foundation.org>
To: Jakub Jelinek <jakub@redhat.com>
Cc: Segher Boessenkool <segher@kernel.crashing.org>,
Peter Zijlstra <peterz@infradead.org>,
Nick Desaulniers <ndesaulniers@google.com>,
Stephane Eranian <eranian@google.com>,
linux-kernel@vger.kernel.org, tony.luck@intel.com,
reinette.chatre@intel.com, fenghua.yu@intel.com,
peternewman@google.com, james.morse@arm.com, babu.moger@amd.com,
ananth.narayan@amd.com, vschneid@redhat.com,
Nathan Chancellor <nathan@kernel.org>,
clang-built-linux <llvm@lists.linux.dev>,
Borislav Petkov <bp@alien8.de>, "H. Peter Anvin" <hpa@zytor.com>,
linux-toolchains@vger.kernel.org
Subject: Re: [PATCH] x86/resctrl: avoid compiler optimization in __resctrl_sched_in
Date: Tue, 7 Mar 2023 13:06:29 -0800 [thread overview]
Message-ID: <CAHk-=whCA4-uc5WV_-68Mpmu-TiSv6fxkSjZ19zzcW9jpSxDvA@mail.gmail.com> (raw)
In-Reply-To: <CAHk-=whOLcy=oz=gHyoSSEnqc3M-APKFKTtTvA_3wYYPV8L+oA@mail.gmail.com>
[-- Attachment #1: Type: text/plain, Size: 721 bytes --]
On Tue, Mar 7, 2023 at 12:54 PM Linus Torvalds
<torvalds@linux-foundation.org> wrote:
>
> I think the problem is that the <asm/resctrl.h> code is disgusting and
> horrible in multiple ways:
>
> (a) it shouldn't define and declare a static function in a header file
>
> (b) the resctrl_sched_in() inline function is misdesigned to begin with
Ok, so here's a *ttoally* untested and mindless patch to maybe fix
what I dislike about that resctl code.
Does it fix the code generation issue? I have no idea. But this is
what I would suggest is the right answer, without actually knowing the
code any better, and just going on a mindless rampage.
It seems to compile for me, fwiw.
Linus
[-- Attachment #2: patch.diff --]
[-- Type: text/x-patch, Size: 3368 bytes --]
arch/x86/include/asm/resctrl.h | 12 ++++++------
arch/x86/kernel/cpu/resctrl/rdtgroup.c | 4 ++--
arch/x86/kernel/process_32.c | 2 +-
arch/x86/kernel/process_64.c | 2 +-
4 files changed, 10 insertions(+), 10 deletions(-)
diff --git a/arch/x86/include/asm/resctrl.h b/arch/x86/include/asm/resctrl.h
index 52788f79786f..255a78d9d906 100644
--- a/arch/x86/include/asm/resctrl.h
+++ b/arch/x86/include/asm/resctrl.h
@@ -49,7 +49,7 @@ DECLARE_STATIC_KEY_FALSE(rdt_mon_enable_key);
* simple as possible.
* Must be called with preemption disabled.
*/
-static void __resctrl_sched_in(void)
+static inline void __resctrl_sched_in(struct task_struct *tsk)
{
struct resctrl_pqr_state *state = this_cpu_ptr(&pqr_state);
u32 closid = state->default_closid;
@@ -61,13 +61,13 @@ static void __resctrl_sched_in(void)
* Else use the closid/rmid assigned to this cpu.
*/
if (static_branch_likely(&rdt_alloc_enable_key)) {
- tmp = READ_ONCE(current->closid);
+ tmp = READ_ONCE(tsk->closid);
if (tmp)
closid = tmp;
}
if (static_branch_likely(&rdt_mon_enable_key)) {
- tmp = READ_ONCE(current->rmid);
+ tmp = READ_ONCE(tsk->rmid);
if (tmp)
rmid = tmp;
}
@@ -88,17 +88,17 @@ static inline unsigned int resctrl_arch_round_mon_val(unsigned int val)
return val * scale;
}
-static inline void resctrl_sched_in(void)
+static inline void resctrl_sched_in(struct task_struct *tsk)
{
if (static_branch_likely(&rdt_enable_key))
- __resctrl_sched_in();
+ __resctrl_sched_in(tsk);
}
void resctrl_cpu_detect(struct cpuinfo_x86 *c);
#else
-static inline void resctrl_sched_in(void) {}
+static inline void resctrl_sched_in(struct task_struct *tsk) {}
static inline void resctrl_cpu_detect(struct cpuinfo_x86 *c) {}
#endif /* CONFIG_X86_CPU_RESCTRL */
diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
index e2c1599d1b37..884b6e9a7e31 100644
--- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
+++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
@@ -314,7 +314,7 @@ static void update_cpu_closid_rmid(void *info)
* executing task might have its own closid selected. Just reuse
* the context switch code.
*/
- resctrl_sched_in();
+ resctrl_sched_in(current);
}
/*
@@ -530,7 +530,7 @@ static void _update_task_closid_rmid(void *task)
* Otherwise, the MSR is updated when the task is scheduled in.
*/
if (task == current)
- resctrl_sched_in();
+ resctrl_sched_in(task);
}
static void update_task_closid_rmid(struct task_struct *t)
diff --git a/arch/x86/kernel/process_32.c b/arch/x86/kernel/process_32.c
index 470c128759ea..708c87b88cc1 100644
--- a/arch/x86/kernel/process_32.c
+++ b/arch/x86/kernel/process_32.c
@@ -212,7 +212,7 @@ __switch_to(struct task_struct *prev_p, struct task_struct *next_p)
switch_fpu_finish();
/* Load the Intel cache allocation PQR MSR. */
- resctrl_sched_in();
+ resctrl_sched_in(next_p);
return prev_p;
}
diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c
index 4e34b3b68ebd..bb65a68b4b49 100644
--- a/arch/x86/kernel/process_64.c
+++ b/arch/x86/kernel/process_64.c
@@ -656,7 +656,7 @@ __switch_to(struct task_struct *prev_p, struct task_struct *next_p)
}
/* Load the Intel cache allocation PQR MSR. */
- resctrl_sched_in();
+ resctrl_sched_in(next_p);
return prev_p;
}
next prev parent reply other threads:[~2023-03-07 21:12 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20230303231133.1486085-1-eranian@google.com>
[not found] ` <20230306120106.GE1267364@hirez.programming.kicks-ass.net>
[not found] ` <CAKwvOdnRvd5KK01awAyeyt5S36TPPW4_8Z6YL1r4gB-pBrHTbg@mail.gmail.com>
2023-03-07 11:35 ` [PATCH] x86/resctrl: avoid compiler optimization in __resctrl_sched_in Peter Zijlstra
2023-03-07 17:48 ` Linus Torvalds
2023-03-07 18:43 ` Segher Boessenkool
2023-03-07 20:43 ` Jakub Jelinek
2023-03-07 20:54 ` Linus Torvalds
2023-03-07 21:06 ` Linus Torvalds [this message]
2023-03-07 21:35 ` Luck, Tony
2023-03-07 21:58 ` Nick Desaulniers
2023-03-08 6:13 ` Stephane Eranian
2023-03-08 23:25 ` Linus Torvalds
2023-03-08 16:02 ` Moger, Babu
2023-03-07 21:11 ` Luck, Tony
2023-03-07 21:14 ` Linus Torvalds
2023-03-07 21:23 ` Luck, Tony
2023-03-08 0:36 ` Luck, Tony
2023-03-07 21:16 ` Nick Desaulniers
2023-03-07 21:19 ` Linus Torvalds
2023-03-07 21:22 ` Nick Desaulniers
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