This patch switches uprobes SRCU usage to RCU Tasks Trace flavor, which
is optimized for more lightweight and quick readers (at the expense of
slower writers, which for uprobes is a fine trade-off) and has better
performance and scalability with number of CPUs.
Similarly to baseline vs SRCU, we've benchmarked SRCU-based
implementation vs RCU Tasks Trace implementation.
SRCU
====
uprobe-nop ( 1 cpus): 3.276 ± 0.005M/s ( 3.276M/s/cpu)
uprobe-nop ( 2 cpus): 4.125 ± 0.002M/s ( 2.063M/s/cpu)
uprobe-nop ( 4 cpus): 7.713 ± 0.002M/s ( 1.928M/s/cpu)
uprobe-nop ( 8 cpus): 8.097 ± 0.006M/s ( 1.012M/s/cpu)
uprobe-nop (16 cpus): 6.501 ± 0.056M/s ( 0.406M/s/cpu)
uprobe-nop (32 cpus): 4.398 ± 0.084M/s ( 0.137M/s/cpu)
uprobe-nop (64 cpus): 6.452 ± 0.000M/s ( 0.101M/s/cpu)
uretprobe-nop ( 1 cpus): 2.055 ± 0.001M/s ( 2.055M/s/cpu)
uretprobe-nop ( 2 cpus): 2.677 ± 0.000M/s ( 1.339M/s/cpu)
uretprobe-nop ( 4 cpus): 4.561 ± 0.003M/s ( 1.140M/s/cpu)
uretprobe-nop ( 8 cpus): 5.291 ± 0.002M/s ( 0.661M/s/cpu)
uretprobe-nop (16 cpus): 5.065 ± 0.019M/s ( 0.317M/s/cpu)
uretprobe-nop (32 cpus): 3.622 ± 0.003M/s ( 0.113M/s/cpu)
uretprobe-nop (64 cpus): 3.723 ± 0.002M/s ( 0.058M/s/cpu)
RCU Tasks Trace
===============
uprobe-nop ( 1 cpus): 3.396 ± 0.002M/s ( 3.396M/s/cpu)
uprobe-nop ( 2 cpus): 4.271 ± 0.006M/s ( 2.135M/s/cpu)
uprobe-nop ( 4 cpus): 8.499 ± 0.015M/s ( 2.125M/s/cpu)
uprobe-nop ( 8 cpus): 10.355 ± 0.028M/s ( 1.294M/s/cpu)
uprobe-nop (16 cpus): 7.615 ± 0.099M/s ( 0.476M/s/cpu)
uprobe-nop (32 cpus): 4.430 ± 0.007M/s ( 0.138M/s/cpu)
uprobe-nop (64 cpus): 6.887 ± 0.020M/s ( 0.108M/s/cpu)
uretprobe-nop ( 1 cpus): 2.174 ± 0.001M/s ( 2.174M/s/cpu)
uretprobe-nop ( 2 cpus): 2.853 ± 0.001M/s ( 1.426M/s/cpu)
uretprobe-nop ( 4 cpus): 4.913 ± 0.002M/s ( 1.228M/s/cpu)
uretprobe-nop ( 8 cpus): 5.883 ± 0.002M/s ( 0.735M/s/cpu)
uretprobe-nop (16 cpus): 5.147 ± 0.001M/s ( 0.322M/s/cpu)
uretprobe-nop (32 cpus): 3.738 ± 0.008M/s ( 0.117M/s/cpu)
uretprobe-nop (64 cpus): 4.397 ± 0.002M/s ( 0.069M/s/cpu)
Peak throughput for uprobes increases from 8 mln/s to 10.3 mln/s
(+28%!), and for uretprobes from 5.3 mln/s to 5.8 mln/s (+11%), as we
have more work to do on uretprobes side.
Even single-thread (no contention) performance is slightly better: 3.276
mln/s to 3.396 mln/s (+3.5%) for uprobes, and 2.055 mln/s to 2.174 mln/s
(+5.8%) for uretprobes.
We also select TASKS_TRACE_RCU for UPROBES in Kconfig due to this
dependency.
Reviewed-by: Masami Hiramatsu (Google) <mhira...@kernel.org>
Reviewed-by: Oleg Nesterov <o...@redhat.com>
Signed-off-by: Andrii Nakryiko <and...@kernel.org>
---
arch/Kconfig | 1 +
kernel/events/uprobes.c | 38 ++++++++++++++++----------------------
2 files changed, 17 insertions(+), 22 deletions(-)
diff --git a/arch/Kconfig b/arch/Kconfig
index 975dd22a2dbd..a0df3f3dc484 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -126,6 +126,7 @@ config KPROBES_ON_FTRACE
config UPROBES
def_bool n
depends on ARCH_SUPPORTS_UPROBES
+ select TASKS_TRACE_RCU
help
Uprobes is the user-space counterpart to kprobes: they
enable instrumentation applications (such as 'perf probe')
diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
index 4b7e590dc428..a2e6a57f79f2 100644
--- a/kernel/events/uprobes.c
+++ b/kernel/events/uprobes.c
@@ -26,6 +26,7 @@
#include <linux/task_work.h>
#include <linux/shmem_fs.h>
#include <linux/khugepaged.h>
+#include <linux/rcupdate_trace.h>
#include <linux/uprobes.h>
@@ -42,8 +43,6 @@ static struct rb_root uprobes_tree = RB_ROOT;
static DEFINE_RWLOCK(uprobes_treelock); /* serialize rbtree access */
static seqcount_rwlock_t uprobes_seqcount =
SEQCNT_RWLOCK_ZERO(uprobes_seqcount, &uprobes_treelock);
-DEFINE_STATIC_SRCU(uprobes_srcu);
-
#define UPROBES_HASH_SZ 13
/* serialize uprobe->pending_list */
static struct mutex uprobes_mmap_mutex[UPROBES_HASH_SZ];
@@ -652,7 +651,7 @@ static void put_uprobe(struct uprobe *uprobe)
delayed_uprobe_remove(uprobe, NULL);
mutex_unlock(&delayed_uprobe_lock);
- call_srcu(&uprobes_srcu, &uprobe->rcu, uprobe_free_rcu);
+ call_rcu_tasks_trace(&uprobe->rcu, uprobe_free_rcu);
}
static __always_inline
@@ -707,7 +706,7 @@ static struct uprobe *find_uprobe_rcu(struct inode *inode,
loff_t offset)
struct rb_node *node;
unsigned int seq;
- lockdep_assert(srcu_read_lock_held(&uprobes_srcu));
+ lockdep_assert(rcu_read_lock_trace_held());
do {
seq = read_seqcount_begin(&uprobes_seqcount);
@@ -935,8 +934,7 @@ static bool filter_chain(struct uprobe *uprobe, struct
mm_struct *mm)
bool ret = false;
down_read(&uprobe->consumer_rwsem);
- list_for_each_entry_srcu(uc, &uprobe->consumers, cons_node,
- srcu_read_lock_held(&uprobes_srcu)) {
+ list_for_each_entry_rcu(uc, &uprobe->consumers, cons_node,
rcu_read_lock_trace_held()) {
ret = consumer_filter(uc, mm);
if (ret)
break;
@@ -1157,7 +1155,7 @@ void uprobe_unregister_sync(void)
* unlucky enough caller can free consumer's memory and cause
* handler_chain() or handle_uretprobe_chain() to do an use-after-free.
*/
- synchronize_srcu(&uprobes_srcu);
+ synchronize_rcu_tasks_trace();
}
EXPORT_SYMBOL_GPL(uprobe_unregister_sync);
@@ -1241,19 +1239,18 @@ EXPORT_SYMBOL_GPL(uprobe_register);
int uprobe_apply(struct uprobe *uprobe, struct uprobe_consumer *uc, bool add)
{
struct uprobe_consumer *con;
- int ret = -ENOENT, srcu_idx;
+ int ret = -ENOENT;
down_write(&uprobe->register_rwsem);
- srcu_idx = srcu_read_lock(&uprobes_srcu);
- list_for_each_entry_srcu(con, &uprobe->consumers, cons_node,
- srcu_read_lock_held(&uprobes_srcu)) {
+ rcu_read_lock_trace();
+ list_for_each_entry_rcu(con, &uprobe->consumers, cons_node,
rcu_read_lock_trace_held()) {
if (con == uc) {
ret = register_for_each_vma(uprobe, add ? uc : NULL);
break;
}
}
- srcu_read_unlock(&uprobes_srcu, srcu_idx);
+ rcu_read_unlock_trace();
up_write(&uprobe->register_rwsem);
@@ -2123,8 +2120,7 @@ static void handler_chain(struct uprobe *uprobe, struct
pt_regs *regs)
current->utask->auprobe = &uprobe->arch;
- list_for_each_entry_srcu(uc, &uprobe->consumers, cons_node,
- srcu_read_lock_held(&uprobes_srcu)) {
+ list_for_each_entry_rcu(uc, &uprobe->consumers, cons_node,
rcu_read_lock_trace_held()) {
int rc = 0;
if (uc->handler) {
@@ -2162,15 +2158,13 @@ handle_uretprobe_chain(struct return_instance *ri,
struct pt_regs *regs)
{
struct uprobe *uprobe = ri->uprobe;
struct uprobe_consumer *uc;
- int srcu_idx;
- srcu_idx = srcu_read_lock(&uprobes_srcu);
- list_for_each_entry_srcu(uc, &uprobe->consumers, cons_node,
- srcu_read_lock_held(&uprobes_srcu)) {
+ rcu_read_lock_trace();
+ list_for_each_entry_rcu(uc, &uprobe->consumers, cons_node,
rcu_read_lock_trace_held()) {
if (uc->ret_handler)
uc->ret_handler(uc, ri->func, regs);
}
- srcu_read_unlock(&uprobes_srcu, srcu_idx);
+ rcu_read_unlock_trace();
}
static struct return_instance *find_next_ret_chain(struct return_instance *ri)
@@ -2255,13 +2249,13 @@ static void handle_swbp(struct pt_regs *regs)
{
struct uprobe *uprobe;
unsigned long bp_vaddr;
- int is_swbp, srcu_idx;
+ int is_swbp;
bp_vaddr = uprobe_get_swbp_addr(regs);
if (bp_vaddr == uprobe_get_trampoline_vaddr())
return uprobe_handle_trampoline(regs);
- srcu_idx = srcu_read_lock(&uprobes_srcu);
+ rcu_read_lock_trace();
uprobe = find_active_uprobe_rcu(bp_vaddr, &is_swbp);
if (!uprobe) {
@@ -2319,7 +2313,7 @@ static void handle_swbp(struct pt_regs *regs)
out:
/* arch_uprobe_skip_sstep() succeeded, or restart if can't singlestep */
- srcu_read_unlock(&uprobes_srcu, srcu_idx);
+ rcu_read_unlock_trace();
}
/*
--
2.43.5
