From: Nadav Amit <namit at vmware.com> This is a respin of a rebased version of an old series, which I did not follow, as I was preoccupied with personal issues (sorry). The series improve TLB shootdown by flushing the local TLB concurrently with remote TLBs, overlapping the IPI delivery time with the local flush. Performance numbers can be found in the previous version [1]. The patches are essentially the same, but rebasing on the last version required some changes. I left the reviewed-by tags - if anyone considers it inappropriate, please let me know (and you have my apology). [1] https://lore.kernel.org/lkml/20190823224153.15223-1-namit at vmware.com/ v4 -> v5: * Rebase on 5.11 * Move concurrent smp logic to smp_call_function_many_cond() * Remove SGI-UV patch which is not needed anymore v3 -> v4: * Merge flush_tlb_func_local and flush_tlb_func_remote() [Peter] * Prevent preemption on_each_cpu(). It is not needed, but it prevents concerns. [Peter/tglx] * Adding acked-, review-by tags v2 -> v3: * Open-code the remote/local-flush decision code [Andy] * Fix hyper-v, Xen implementations [Andrew] * Fix redundant TLB flushes. v1 -> v2: * Removing the patches that Thomas took [tglx] * Adding hyper-v, Xen compile-tested implementations [Dave] * Removing UV [Andy] * Adding lazy optimization, removing inline keyword [Dave] * Restructuring patch-set RFCv2 -> v1: * Fix comment on flush_tlb_multi [Juergen] * Removing async invalidation optimizations [Andy] * Adding KVM support [Paolo] Cc: Andy Lutomirski <luto at kernel.org> Cc: Borislav Petkov <bp at alien8.de> Cc: Boris Ostrovsky <boris.ostrovsky at oracle.com> Cc: Dave Hansen <dave.hansen at linux.intel.com> Cc: Haiyang Zhang <haiyangz at microsoft.com> Cc: Ingo Molnar <mingo at redhat.com> Cc: Josh Poimboeuf <jpoimboe at redhat.com> Cc: Juergen Gross <jgross at suse.com> Cc: "K. Y. Srinivasan" <kys at microsoft.com> Cc: Paolo Bonzini <pbonzini at redhat.com> Cc: Peter Zijlstra <peterz at infradead.org> Cc: Rik van Riel <riel at surriel.com> Cc: Sasha Levin <sashal at kernel.org> Cc: Stephen Hemminger <sthemmin at microsoft.com> Cc: Thomas Gleixner <tglx at linutronix.de> Cc: kvm at vger.kernel.org Cc: linux-hyperv at vger.kernel.org Cc: linux-kernel at vger.kernel.org Cc: virtualization at lists.linux-foundation.org Cc: x86 at kernel.org Cc: xen-devel at lists.xenproject.org Nadav Amit (8): smp: Run functions concurrently in smp_call_function_many_cond() x86/mm/tlb: Unify flush_tlb_func_local() and flush_tlb_func_remote() x86/mm/tlb: Open-code on_each_cpu_cond_mask() for tlb_is_not_lazy() x86/mm/tlb: Flush remote and local TLBs concurrently x86/mm/tlb: Privatize cpu_tlbstate x86/mm/tlb: Do not make is_lazy dirty for no reason cpumask: Mark functions as pure x86/mm/tlb: Remove unnecessary uses of the inline keyword arch/x86/hyperv/mmu.c | 10 +- arch/x86/include/asm/paravirt.h | 6 +- arch/x86/include/asm/paravirt_types.h | 4 +- arch/x86/include/asm/tlbflush.h | 48 +++---- arch/x86/include/asm/trace/hyperv.h | 2 +- arch/x86/kernel/alternative.c | 2 +- arch/x86/kernel/kvm.c | 11 +- arch/x86/mm/init.c | 2 +- arch/x86/mm/tlb.c | 177 +++++++++++++++----------- arch/x86/xen/mmu_pv.c | 11 +- include/linux/cpumask.h | 6 +- include/trace/events/xen.h | 2 +- kernel/smp.c | 148 +++++++++++---------- 13 files changed, 242 insertions(+), 187 deletions(-) -- 2.25.1
Nadav Amit
2021-Feb-09 22:16 UTC
[PATCH v5 4/8] x86/mm/tlb: Flush remote and local TLBs concurrently
From: Nadav Amit <namit at vmware.com>
To improve TLB shootdown performance, flush the remote and local TLBs
concurrently. Introduce flush_tlb_multi() that does so. Introduce
paravirtual versions of flush_tlb_multi() for KVM, Xen and hyper-v (Xen
and hyper-v are only compile-tested).
While the updated smp infrastructure is capable of running a function on
a single local core, it is not optimized for this case. The multiple
function calls and the indirect branch introduce some overhead, and
might make local TLB flushes slower than they were before the recent
changes.
Before calling the SMP infrastructure, check if only a local TLB flush
is needed to restore the lost performance in this common case. This
requires to check mm_cpumask() one more time, but unless this mask is
updated very frequently, this should impact performance negatively.
Cc: "K. Y. Srinivasan" <kys at microsoft.com>
Cc: Haiyang Zhang <haiyangz at microsoft.com>
Cc: Stephen Hemminger <sthemmin at microsoft.com>
Cc: Sasha Levin <sashal at kernel.org>
Cc: Thomas Gleixner <tglx at linutronix.de>
Cc: Ingo Molnar <mingo at redhat.com>
Cc: Borislav Petkov <bp at alien8.de>
Cc: x86 at kernel.org
Cc: Juergen Gross <jgross at suse.com>
Cc: Paolo Bonzini <pbonzini at redhat.com>
Cc: Andy Lutomirski <luto at kernel.org>
Cc: Peter Zijlstra <peterz at infradead.org>
Cc: Boris Ostrovsky <boris.ostrovsky at oracle.com>
Cc: linux-hyperv at vger.kernel.org
Cc: linux-kernel at vger.kernel.org
Cc: virtualization at lists.linux-foundation.org
Cc: kvm at vger.kernel.org
Cc: xen-devel at lists.xenproject.org
Reviewed-by: Michael Kelley <mikelley at microsoft.com> # Hyper-v parts
Reviewed-by: Juergen Gross <jgross at suse.com> # Xen and paravirt parts
Reviewed-by: Dave Hansen <dave.hansen at linux.intel.com>
Signed-off-by: Nadav Amit <namit at vmware.com>
---
arch/x86/hyperv/mmu.c | 10 +++---
arch/x86/include/asm/paravirt.h | 6 ++--
arch/x86/include/asm/paravirt_types.h | 4 +--
arch/x86/include/asm/tlbflush.h | 4 +--
arch/x86/include/asm/trace/hyperv.h | 2 +-
arch/x86/kernel/kvm.c | 11 ++++--
arch/x86/mm/tlb.c | 49 +++++++++++++++++----------
arch/x86/xen/mmu_pv.c | 11 +++---
include/trace/events/xen.h | 2 +-
9 files changed, 58 insertions(+), 41 deletions(-)
diff --git a/arch/x86/hyperv/mmu.c b/arch/x86/hyperv/mmu.c
index 2c87350c1fb0..681dba8de4f2 100644
--- a/arch/x86/hyperv/mmu.c
+++ b/arch/x86/hyperv/mmu.c
@@ -52,8 +52,8 @@ static inline int fill_gva_list(u64 gva_list[], int offset,
return gva_n - offset;
}
-static void hyperv_flush_tlb_others(const struct cpumask *cpus,
- const struct flush_tlb_info *info)
+static void hyperv_flush_tlb_multi(const struct cpumask *cpus,
+ const struct flush_tlb_info *info)
{
int cpu, vcpu, gva_n, max_gvas;
struct hv_tlb_flush **flush_pcpu;
@@ -61,7 +61,7 @@ static void hyperv_flush_tlb_others(const struct cpumask
*cpus,
u64 status = U64_MAX;
unsigned long flags;
- trace_hyperv_mmu_flush_tlb_others(cpus, info);
+ trace_hyperv_mmu_flush_tlb_multi(cpus, info);
if (!hv_hypercall_pg)
goto do_native;
@@ -164,7 +164,7 @@ static void hyperv_flush_tlb_others(const struct cpumask
*cpus,
if (!(status & HV_HYPERCALL_RESULT_MASK))
return;
do_native:
- native_flush_tlb_others(cpus, info);
+ native_flush_tlb_multi(cpus, info);
}
static u64 hyperv_flush_tlb_others_ex(const struct cpumask *cpus,
@@ -239,6 +239,6 @@ void hyperv_setup_mmu_ops(void)
return;
pr_info("Using hypercall for remote TLB flush\n");
- pv_ops.mmu.flush_tlb_others = hyperv_flush_tlb_others;
+ pv_ops.mmu.flush_tlb_multi = hyperv_flush_tlb_multi;
pv_ops.mmu.tlb_remove_table = tlb_remove_table;
}
diff --git a/arch/x86/include/asm/paravirt.h b/arch/x86/include/asm/paravirt.h
index f8dce11d2bc1..515e49204c8b 100644
--- a/arch/x86/include/asm/paravirt.h
+++ b/arch/x86/include/asm/paravirt.h
@@ -50,7 +50,7 @@ static inline void slow_down_io(void)
void native_flush_tlb_local(void);
void native_flush_tlb_global(void);
void native_flush_tlb_one_user(unsigned long addr);
-void native_flush_tlb_others(const struct cpumask *cpumask,
+void native_flush_tlb_multi(const struct cpumask *cpumask,
const struct flush_tlb_info *info);
static inline void __flush_tlb_local(void)
@@ -68,10 +68,10 @@ static inline void __flush_tlb_one_user(unsigned long addr)
PVOP_VCALL1(mmu.flush_tlb_one_user, addr);
}
-static inline void __flush_tlb_others(const struct cpumask *cpumask,
+static inline void __flush_tlb_multi(const struct cpumask *cpumask,
const struct flush_tlb_info *info)
{
- PVOP_VCALL2(mmu.flush_tlb_others, cpumask, info);
+ PVOP_VCALL2(mmu.flush_tlb_multi, cpumask, info);
}
static inline void paravirt_tlb_remove_table(struct mmu_gather *tlb, void
*table)
diff --git a/arch/x86/include/asm/paravirt_types.h
b/arch/x86/include/asm/paravirt_types.h
index b6b02b7c19cc..541fe7193526 100644
--- a/arch/x86/include/asm/paravirt_types.h
+++ b/arch/x86/include/asm/paravirt_types.h
@@ -201,8 +201,8 @@ struct pv_mmu_ops {
void (*flush_tlb_user)(void);
void (*flush_tlb_kernel)(void);
void (*flush_tlb_one_user)(unsigned long addr);
- void (*flush_tlb_others)(const struct cpumask *cpus,
- const struct flush_tlb_info *info);
+ void (*flush_tlb_multi)(const struct cpumask *cpus,
+ const struct flush_tlb_info *info);
void (*tlb_remove_table)(struct mmu_gather *tlb, void *table);
diff --git a/arch/x86/include/asm/tlbflush.h b/arch/x86/include/asm/tlbflush.h
index a7a598af116d..3c6681def912 100644
--- a/arch/x86/include/asm/tlbflush.h
+++ b/arch/x86/include/asm/tlbflush.h
@@ -175,7 +175,7 @@ extern void initialize_tlbstate_and_flush(void);
* - flush_tlb_page(vma, vmaddr) flushes one page
* - flush_tlb_range(vma, start, end) flushes a range of pages
* - flush_tlb_kernel_range(start, end) flushes a range of kernel pages
- * - flush_tlb_others(cpumask, info) flushes TLBs on other cpus
+ * - flush_tlb_multi(cpumask, info) flushes TLBs on multiple cpus
*
* ..but the i386 has somewhat limited tlb flushing capabilities,
* and page-granular flushes are available only on i486 and up.
@@ -209,7 +209,7 @@ struct flush_tlb_info {
void flush_tlb_local(void);
void flush_tlb_one_user(unsigned long addr);
void flush_tlb_one_kernel(unsigned long addr);
-void flush_tlb_others(const struct cpumask *cpumask,
+void flush_tlb_multi(const struct cpumask *cpumask,
const struct flush_tlb_info *info);
#ifdef CONFIG_PARAVIRT
diff --git a/arch/x86/include/asm/trace/hyperv.h
b/arch/x86/include/asm/trace/hyperv.h
index 4d705cb4d63b..a8e5a7a2b460 100644
--- a/arch/x86/include/asm/trace/hyperv.h
+++ b/arch/x86/include/asm/trace/hyperv.h
@@ -8,7 +8,7 @@
#if IS_ENABLED(CONFIG_HYPERV)
-TRACE_EVENT(hyperv_mmu_flush_tlb_others,
+TRACE_EVENT(hyperv_mmu_flush_tlb_multi,
TP_PROTO(const struct cpumask *cpus,
const struct flush_tlb_info *info),
TP_ARGS(cpus, info),
diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c
index 5e78e01ca3b4..38ea9dee2456 100644
--- a/arch/x86/kernel/kvm.c
+++ b/arch/x86/kernel/kvm.c
@@ -613,7 +613,7 @@ static int kvm_cpu_down_prepare(unsigned int cpu)
}
#endif
-static void kvm_flush_tlb_others(const struct cpumask *cpumask,
+static void kvm_flush_tlb_multi(const struct cpumask *cpumask,
const struct flush_tlb_info *info)
{
u8 state;
@@ -627,6 +627,11 @@ static void kvm_flush_tlb_others(const struct cpumask
*cpumask,
* queue flush_on_enter for pre-empted vCPUs
*/
for_each_cpu(cpu, flushmask) {
+ /*
+ * The local vCPU is never preempted, so we do not explicitly
+ * skip check for local vCPU - it will never be cleared from
+ * flushmask.
+ */
src = &per_cpu(steal_time, cpu);
state = READ_ONCE(src->preempted);
if ((state & KVM_VCPU_PREEMPTED)) {
@@ -636,7 +641,7 @@ static void kvm_flush_tlb_others(const struct cpumask
*cpumask,
}
}
- native_flush_tlb_others(flushmask, info);
+ native_flush_tlb_multi(flushmask, info);
}
static void __init kvm_guest_init(void)
@@ -654,7 +659,7 @@ static void __init kvm_guest_init(void)
}
if (pv_tlb_flush_supported()) {
- pv_ops.mmu.flush_tlb_others = kvm_flush_tlb_others;
+ pv_ops.mmu.flush_tlb_multi = kvm_flush_tlb_multi;
pv_ops.mmu.tlb_remove_table = tlb_remove_table;
pr_info("KVM setup pv remote TLB flush\n");
}
diff --git a/arch/x86/mm/tlb.c b/arch/x86/mm/tlb.c
index 07b6701a540a..78fcbd58716e 100644
--- a/arch/x86/mm/tlb.c
+++ b/arch/x86/mm/tlb.c
@@ -24,7 +24,7 @@
# define __flush_tlb_local native_flush_tlb_local
# define __flush_tlb_global native_flush_tlb_global
# define __flush_tlb_one_user(addr) native_flush_tlb_one_user(addr)
-# define __flush_tlb_others(msk, info) native_flush_tlb_others(msk, info)
+# define __flush_tlb_multi(msk, info) native_flush_tlb_multi(msk, info)
#endif
/*
@@ -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
- * from cpu_tlbstate.is_lazy whether or not to send an IPI.
+ * cpu_tlbstate.is_lazy whether or not to send an IPI.
*/
if (WARN_ON_ONCE(real_prev != &init_mm &&
!cpumask_test_cpu(cpu, mm_cpumask(next))))
@@ -697,7 +697,7 @@ static void flush_tlb_func(void *info)
* garbage into our TLB. Since switching to init_mm is barely
* slower than a minimal flush, just switch to init_mm.
*
- * This should be rare, with native_flush_tlb_others skipping
+ * This should be rare, with native_flush_tlb_multi() skipping
* IPIs to lazy TLB mode CPUs.
*/
switch_mm_irqs_off(NULL, &init_mm, NULL);
@@ -795,9 +795,14 @@ static bool tlb_is_not_lazy(int cpu)
static DEFINE_PER_CPU(cpumask_t, flush_tlb_mask);
-STATIC_NOPV void native_flush_tlb_others(const struct cpumask *cpumask,
+STATIC_NOPV void native_flush_tlb_multi(const struct cpumask *cpumask,
const struct flush_tlb_info *info)
{
+ /*
+ * Do accounting and tracing. Note that there are (and have always been)
+ * cases in which a remote TLB flush will be traced, but eventually
+ * would not happen.
+ */
count_vm_tlb_event(NR_TLB_REMOTE_FLUSH);
if (info->end == TLB_FLUSH_ALL)
trace_tlb_flush(TLB_REMOTE_SEND_IPI, TLB_FLUSH_ALL);
@@ -816,8 +821,8 @@ STATIC_NOPV void native_flush_tlb_others(const struct
cpumask *cpumask,
* doing a speculative memory access.
*/
if (info->freed_tables) {
- smp_call_function_many(cpumask, flush_tlb_func,
- (void *)info, 1);
+ on_each_cpu_cond_mask(NULL, flush_tlb_func, (void *)info, true,
+ cpumask);
} else {
/*
* Although we could have used on_each_cpu_cond_mask(),
@@ -844,14 +849,15 @@ STATIC_NOPV void native_flush_tlb_others(const struct
cpumask *cpumask,
if (tlb_is_not_lazy(cpu))
__cpumask_set_cpu(cpu, cond_cpumask);
}
- smp_call_function_many(cond_cpumask, flush_tlb_func, (void *)info, 1);
+ on_each_cpu_cond_mask(NULL, flush_tlb_func, (void *)info, true,
+ cpumask);
}
}
-void flush_tlb_others(const struct cpumask *cpumask,
+void flush_tlb_multi(const struct cpumask *cpumask,
const struct flush_tlb_info *info)
{
- __flush_tlb_others(cpumask, info);
+ __flush_tlb_multi(cpumask, info);
}
/*
@@ -931,16 +937,20 @@ void flush_tlb_mm_range(struct mm_struct *mm, unsigned
long start,
info = get_flush_tlb_info(mm, start, end, stride_shift, freed_tables,
new_tlb_gen);
- if (mm == this_cpu_read(cpu_tlbstate.loaded_mm)) {
+ /*
+ * flush_tlb_multi() is not optimized for the common case in which only
+ * a local TLB flush is needed. Optimize this use-case by calling
+ * flush_tlb_func_local() directly in this case.
+ */
+ if (cpumask_any_but(mm_cpumask(mm), cpu) < nr_cpu_ids) {
+ flush_tlb_multi(mm_cpumask(mm), info);
+ } else if (mm == this_cpu_read(cpu_tlbstate.loaded_mm)) {
lockdep_assert_irqs_enabled();
local_irq_disable();
flush_tlb_func(info);
local_irq_enable();
}
- if (cpumask_any_but(mm_cpumask(mm), cpu) < nr_cpu_ids)
- flush_tlb_others(mm_cpumask(mm), info);
-
put_flush_tlb_info();
put_cpu();
}
@@ -1151,17 +1161,20 @@ void arch_tlbbatch_flush(struct
arch_tlbflush_unmap_batch *batch)
int cpu = get_cpu();
- info = get_flush_tlb_info(NULL, 0, TLB_FLUSH_ALL, 0, false, 0);
- if (cpumask_test_cpu(cpu, &batch->cpumask)) {
+ /*
+ * flush_tlb_multi() is not optimized for the common case in which only
+ * a local TLB flush is needed. Optimize this use-case by calling
+ * flush_tlb_func_local() directly in this case.
+ */
+ if (cpumask_any_but(&batch->cpumask, cpu) < nr_cpu_ids) {
+ flush_tlb_multi(&batch->cpumask, info);
+ } else if (cpumask_test_cpu(cpu, &batch->cpumask)) {
lockdep_assert_irqs_enabled();
local_irq_disable();
flush_tlb_func(info);
local_irq_enable();
}
- if (cpumask_any_but(&batch->cpumask, cpu) < nr_cpu_ids)
- flush_tlb_others(&batch->cpumask, info);
-
cpumask_clear(&batch->cpumask);
put_flush_tlb_info();
diff --git a/arch/x86/xen/mmu_pv.c b/arch/x86/xen/mmu_pv.c
index cf2ade864c30..09b95c0e876e 100644
--- a/arch/x86/xen/mmu_pv.c
+++ b/arch/x86/xen/mmu_pv.c
@@ -1247,8 +1247,8 @@ static void xen_flush_tlb_one_user(unsigned long addr)
preempt_enable();
}
-static void xen_flush_tlb_others(const struct cpumask *cpus,
- const struct flush_tlb_info *info)
+static void xen_flush_tlb_multi(const struct cpumask *cpus,
+ const struct flush_tlb_info *info)
{
struct {
struct mmuext_op op;
@@ -1258,7 +1258,7 @@ static void xen_flush_tlb_others(const struct cpumask
*cpus,
const size_t mc_entry_size = sizeof(args->op) +
sizeof(args->mask[0]) * BITS_TO_LONGS(num_possible_cpus());
- trace_xen_mmu_flush_tlb_others(cpus, info->mm, info->start,
info->end);
+ trace_xen_mmu_flush_tlb_multi(cpus, info->mm, info->start,
info->end);
if (cpumask_empty(cpus))
return; /* nothing to do */
@@ -1267,9 +1267,8 @@ static void xen_flush_tlb_others(const struct cpumask
*cpus,
args = mcs.args;
args->op.arg2.vcpumask = to_cpumask(args->mask);
- /* Remove us, and any offline CPUS. */
+ /* Remove any offline CPUs */
cpumask_and(to_cpumask(args->mask), cpus, cpu_online_mask);
- cpumask_clear_cpu(smp_processor_id(), to_cpumask(args->mask));
args->op.cmd = MMUEXT_TLB_FLUSH_MULTI;
if (info->end != TLB_FLUSH_ALL &&
@@ -2086,7 +2085,7 @@ static const struct pv_mmu_ops xen_mmu_ops __initconst = {
.flush_tlb_user = xen_flush_tlb,
.flush_tlb_kernel = xen_flush_tlb,
.flush_tlb_one_user = xen_flush_tlb_one_user,
- .flush_tlb_others = xen_flush_tlb_others,
+ .flush_tlb_multi = xen_flush_tlb_multi,
.tlb_remove_table = tlb_remove_table,
.pgd_alloc = xen_pgd_alloc,
diff --git a/include/trace/events/xen.h b/include/trace/events/xen.h
index 3b61b587e137..44a3f565264d 100644
--- a/include/trace/events/xen.h
+++ b/include/trace/events/xen.h
@@ -346,7 +346,7 @@ TRACE_EVENT(xen_mmu_flush_tlb_one_user,
TP_printk("addr %lx", __entry->addr)
);
-TRACE_EVENT(xen_mmu_flush_tlb_others,
+TRACE_EVENT(xen_mmu_flush_tlb_multi,
TP_PROTO(const struct cpumask *cpus, struct mm_struct *mm,
unsigned long addr, unsigned long end),
TP_ARGS(cpus, mm, addr, end),
--
2.25.1