lkml.org 
[lkml]   [2021]   [Mar]   [6]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
Date
From
Subject[tip: x86/mm] x86/mm/tlb: Privatize cpu_tlbstate
The following commit has been merged into the x86/mm branch of tip:

Commit-ID: 2f4305b19fe6a2a261d76c21856c5598f7d878fe
Gitweb: https://git.kernel.org/tip/2f4305b19fe6a2a261d76c21856c5598f7d878fe
Author: Nadav Amit <namit@vmware.com>
AuthorDate: Sat, 20 Feb 2021 15:17:08 -08:00
Committer: Ingo Molnar <mingo@kernel.org>
CommitterDate: Sat, 06 Mar 2021 12:59:10 +01:00

x86/mm/tlb: Privatize cpu_tlbstate

cpu_tlbstate is mostly private and only the variable is_lazy is shared.
This causes some false-sharing when TLB flushes are performed.

Break cpu_tlbstate intro cpu_tlbstate and cpu_tlbstate_shared, and mark
each one accordingly.

Signed-off-by: Nadav Amit <namit@vmware.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Dave Hansen <dave.hansen@linux.intel.com>
Link: https://lore.kernel.org/r/20210220231712.2475218-6-namit@vmware.com
---
arch/x86/include/asm/tlbflush.h | 39 +++++++++++++++++---------------
arch/x86/kernel/alternative.c | 2 +-
arch/x86/mm/init.c | 2 +-
arch/x86/mm/tlb.c | 17 ++++++++------
4 files changed, 33 insertions(+), 27 deletions(-)

diff --git a/arch/x86/include/asm/tlbflush.h b/arch/x86/include/asm/tlbflush.h
index 3c6681d..fa952ea 100644
--- a/arch/x86/include/asm/tlbflush.h
+++ b/arch/x86/include/asm/tlbflush.h
@@ -90,23 +90,6 @@ struct tlb_state {
u16 next_asid;

/*
- * We can be in one of several states:
- *
- * - Actively using an mm. Our CPU's bit will be set in
- * mm_cpumask(loaded_mm) and is_lazy == false;
- *
- * - Not using a real mm. loaded_mm == &init_mm. Our CPU's bit
- * will not be set in mm_cpumask(&init_mm) and is_lazy == false.
- *
- * - Lazily using a real mm. loaded_mm != &init_mm, our bit
- * is set in mm_cpumask(loaded_mm), but is_lazy == true.
- * We're heuristically guessing that the CR3 load we
- * skipped more than makes up for the overhead added by
- * lazy mode.
- */
- bool is_lazy;
-
- /*
* If set we changed the page tables in such a way that we
* needed an invalidation of all contexts (aka. PCIDs / ASIDs).
* This tells us to go invalidate all the non-loaded ctxs[]
@@ -151,7 +134,27 @@ struct tlb_state {
*/
struct tlb_context ctxs[TLB_NR_DYN_ASIDS];
};
-DECLARE_PER_CPU_SHARED_ALIGNED(struct tlb_state, cpu_tlbstate);
+DECLARE_PER_CPU_ALIGNED(struct tlb_state, cpu_tlbstate);
+
+struct tlb_state_shared {
+ /*
+ * We can be in one of several states:
+ *
+ * - Actively using an mm. Our CPU's bit will be set in
+ * mm_cpumask(loaded_mm) and is_lazy == false;
+ *
+ * - Not using a real mm. loaded_mm == &init_mm. Our CPU's bit
+ * will not be set in mm_cpumask(&init_mm) and is_lazy == false.
+ *
+ * - Lazily using a real mm. loaded_mm != &init_mm, our bit
+ * is set in mm_cpumask(loaded_mm), but is_lazy == true.
+ * We're heuristically guessing that the CR3 load we
+ * skipped more than makes up for the overhead added by
+ * lazy mode.
+ */
+ bool is_lazy;
+};
+DECLARE_PER_CPU_SHARED_ALIGNED(struct tlb_state_shared, cpu_tlbstate_shared);

bool nmi_uaccess_okay(void);
#define nmi_uaccess_okay nmi_uaccess_okay
diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c
index 8d778e4..94649f8 100644
--- a/arch/x86/kernel/alternative.c
+++ b/arch/x86/kernel/alternative.c
@@ -813,7 +813,7 @@ static inline temp_mm_state_t use_temporary_mm(struct mm_struct *mm)
* with a stale address space WITHOUT being in lazy mode after
* restoring the previous mm.
*/
- if (this_cpu_read(cpu_tlbstate.is_lazy))
+ if (this_cpu_read(cpu_tlbstate_shared.is_lazy))
leave_mm(smp_processor_id());

temp_state.mm = this_cpu_read(cpu_tlbstate.loaded_mm);
diff --git a/arch/x86/mm/init.c b/arch/x86/mm/init.c
index dd694fb..ed2e367 100644
--- a/arch/x86/mm/init.c
+++ b/arch/x86/mm/init.c
@@ -1017,7 +1017,7 @@ void __init zone_sizes_init(void)
free_area_init(max_zone_pfns);
}

-__visible DEFINE_PER_CPU_SHARED_ALIGNED(struct tlb_state, cpu_tlbstate) = {
+__visible DEFINE_PER_CPU_ALIGNED(struct tlb_state, cpu_tlbstate) = {
.loaded_mm = &init_mm,
.next_asid = 1,
.cr4 = ~0UL, /* fail hard if we screw up cr4 shadow initialization */
diff --git a/arch/x86/mm/tlb.c b/arch/x86/mm/tlb.c
index 8db87cd..345a0af 100644
--- a/arch/x86/mm/tlb.c
+++ b/arch/x86/mm/tlb.c
@@ -300,7 +300,7 @@ void leave_mm(int cpu)
return;

/* Warn if we're not lazy. */
- WARN_ON(!this_cpu_read(cpu_tlbstate.is_lazy));
+ WARN_ON(!this_cpu_read(cpu_tlbstate_shared.is_lazy));

switch_mm(NULL, &init_mm, NULL);
}
@@ -424,7 +424,7 @@ void switch_mm_irqs_off(struct mm_struct *prev, struct mm_struct *next,
{
struct mm_struct *real_prev = this_cpu_read(cpu_tlbstate.loaded_mm);
u16 prev_asid = this_cpu_read(cpu_tlbstate.loaded_mm_asid);
- bool was_lazy = this_cpu_read(cpu_tlbstate.is_lazy);
+ bool was_lazy = this_cpu_read(cpu_tlbstate_shared.is_lazy);
unsigned cpu = smp_processor_id();
u64 next_tlb_gen;
bool need_flush;
@@ -469,7 +469,7 @@ void switch_mm_irqs_off(struct mm_struct *prev, struct mm_struct *next,
__flush_tlb_all();
}
#endif
- this_cpu_write(cpu_tlbstate.is_lazy, false);
+ this_cpu_write(cpu_tlbstate_shared.is_lazy, false);

/*
* The membarrier system call requires a full memory barrier and
@@ -490,7 +490,7 @@ void switch_mm_irqs_off(struct mm_struct *prev, struct mm_struct *next,
/*
* Even in lazy TLB mode, the CPU should stay set in the
* mm_cpumask. The TLB shootdown code can figure out from
- * cpu_tlbstate.is_lazy whether or not to send an IPI.
+ * cpu_tlbstate_shared.is_lazy whether or not to send an IPI.
*/
if (WARN_ON_ONCE(real_prev != &init_mm &&
!cpumask_test_cpu(cpu, mm_cpumask(next))))
@@ -598,7 +598,7 @@ void enter_lazy_tlb(struct mm_struct *mm, struct task_struct *tsk)
if (this_cpu_read(cpu_tlbstate.loaded_mm) == &init_mm)
return;

- this_cpu_write(cpu_tlbstate.is_lazy, true);
+ this_cpu_write(cpu_tlbstate_shared.is_lazy, true);
}

/*
@@ -690,7 +690,7 @@ static void flush_tlb_func(void *info)
VM_WARN_ON(this_cpu_read(cpu_tlbstate.ctxs[loaded_mm_asid].ctx_id) !=
loaded_mm->context.ctx_id);

- if (this_cpu_read(cpu_tlbstate.is_lazy)) {
+ if (this_cpu_read(cpu_tlbstate_shared.is_lazy)) {
/*
* We're in lazy mode. We need to at least flush our
* paging-structure cache to avoid speculatively reading
@@ -790,11 +790,14 @@ done:

static bool tlb_is_not_lazy(int cpu)
{
- return !per_cpu(cpu_tlbstate.is_lazy, cpu);
+ return !per_cpu(cpu_tlbstate_shared.is_lazy, cpu);
}

static DEFINE_PER_CPU(cpumask_t, flush_tlb_mask);

+DEFINE_PER_CPU_SHARED_ALIGNED(struct tlb_state_shared, cpu_tlbstate_shared);
+EXPORT_PER_CPU_SYMBOL(cpu_tlbstate_shared);
+
STATIC_NOPV void native_flush_tlb_multi(const struct cpumask *cpumask,
const struct flush_tlb_info *info)
{
\
 
 \ /
  Last update: 2021-03-06 13:15    [W:0.592 / U:0.260 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site