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 tradeof) 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.
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
---
kernel/events/uprobes.c | 37 +++++++++++++++----------------------
1 file changed, 15 insertions(+), 22 deletions(-)
diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
index 8a464cf38127..a5d39cec53d5 100644
--- a/kernel/events/uprobes.c
+++ b/kernel/events/uprobes.c
@@ -42,8 +42,6 @@ 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 +650,7 @@ 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 +705,7 @@ 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 +933,7 @@ 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 +1154,7 @@ 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 +1238,18 @@ 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 +2119,7 @@ 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 +2157,13 @@ 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 +2248,13 @@ 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 +2312,7 @@ 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
Hi Andrii,
kernel test robot noticed the following build errors:
[auto build test ERROR on tip/perf/core]
[also build test ERROR on next-20240830]
[cannot apply to perf-tools-next/perf-tools-next perf-tools/perf-tools linus/master acme/perf/core v6.11-rc5]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]
url: https://github.com/intel-lab-lkp/linux/commits/Andrii-Nakryiko/uprobes-revamp-uprobe-refcounting-and-lifetime-management/20240830-024135
base: tip/perf/core
patch link: https://lore.kernel.org/r/20240829183741.3331213-9-andrii%40kernel.org
patch subject: [PATCH v4 8/8] uprobes: switch to RCU Tasks Trace flavor for better performance
config: x86_64-defconfig (https://download.01.org/0day-ci/archive/20240831/202408310111.2dkrylJ9-lkp@intel.com/config)
compiler: gcc-11 (Debian 11.3.0-12) 11.3.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20240831/202408310111.2dkrylJ9-lkp@intel.com/reproduce)
If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202408310111.2dkrylJ9-lkp@intel.com/
All errors (new ones prefixed by >>):
kernel/events/uprobes.c: In function 'uprobe_unregister_sync':
>> kernel/events/uprobes.c:1157:9: error: implicit declaration of function 'synchronize_rcu_tasks_trace'; did you mean 'synchronize_rcu_tasks'? [-Werror=implicit-function-declaration]
1157 | synchronize_rcu_tasks_trace();
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~
| synchronize_rcu_tasks
cc1: some warnings being treated as errors
vim +1157 kernel/events/uprobes.c
1145
1146 void uprobe_unregister_sync(void)
1147 {
1148 /*
1149 * Now that handler_chain() and handle_uretprobe_chain() iterate over
1150 * uprobe->consumers list under RCU protection without holding
1151 * uprobe->register_rwsem, we need to wait for RCU grace period to
1152 * make sure that we can't call into just unregistered
1153 * uprobe_consumer's callbacks anymore. If we don't do that, fast and
1154 * unlucky enough caller can free consumer's memory and cause
1155 * handler_chain() or handle_uretprobe_chain() to do an use-after-free.
1156 */
> 1157 synchronize_rcu_tasks_trace();
1158 }
1159 EXPORT_SYMBOL_GPL(uprobe_unregister_sync);
1160
--
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki
Hi Andrii,
kernel test robot noticed the following build errors:
[auto build test ERROR on tip/perf/core]
[also build test ERROR on next-20240830]
[cannot apply to perf-tools-next/perf-tools-next perf-tools/perf-tools linus/master acme/perf/core v6.11-rc5]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]
url: https://github.com/intel-lab-lkp/linux/commits/Andrii-Nakryiko/uprobes-revamp-uprobe-refcounting-and-lifetime-management/20240830-024135
base: tip/perf/core
patch link: https://lore.kernel.org/r/20240829183741.3331213-9-andrii%40kernel.org
patch subject: [PATCH v4 8/8] uprobes: switch to RCU Tasks Trace flavor for better performance
config: i386-buildonly-randconfig-004-20240830 (https://download.01.org/0day-ci/archive/20240831/202408310130.t9EBKteQ-lkp@intel.com/config)
compiler: clang version 18.1.5 (https://github.com/llvm/llvm-project 617a15a9eac96088ae5e9134248d8236e34b91b1)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20240831/202408310130.t9EBKteQ-lkp@intel.com/reproduce)
If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202408310130.t9EBKteQ-lkp@intel.com/
All errors (new ones prefixed by >>):
>> kernel/events/uprobes.c:1157:2: error: call to undeclared function 'synchronize_rcu_tasks_trace'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]
1157 | synchronize_rcu_tasks_trace();
| ^
kernel/events/uprobes.c:1157:2: note: did you mean 'synchronize_rcu_tasks_rude'?
include/linux/rcupdate.h:206:6: note: 'synchronize_rcu_tasks_rude' declared here
206 | void synchronize_rcu_tasks_rude(void);
| ^
1 error generated.
vim +/synchronize_rcu_tasks_trace +1157 kernel/events/uprobes.c
1145
1146 void uprobe_unregister_sync(void)
1147 {
1148 /*
1149 * Now that handler_chain() and handle_uretprobe_chain() iterate over
1150 * uprobe->consumers list under RCU protection without holding
1151 * uprobe->register_rwsem, we need to wait for RCU grace period to
1152 * make sure that we can't call into just unregistered
1153 * uprobe_consumer's callbacks anymore. If we don't do that, fast and
1154 * unlucky enough caller can free consumer's memory and cause
1155 * handler_chain() or handle_uretprobe_chain() to do an use-after-free.
1156 */
> 1157 synchronize_rcu_tasks_trace();
1158 }
1159 EXPORT_SYMBOL_GPL(uprobe_unregister_sync);
1160
--
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki
On Fri, Aug 30, 2024 at 10:42 AM kernel test robot <lkp@intel.com> wrote:
>
> Hi Andrii,
>
> kernel test robot noticed the following build errors:
>
> [auto build test ERROR on tip/perf/core]
> [also build test ERROR on next-20240830]
> [cannot apply to perf-tools-next/perf-tools-next perf-tools/perf-tools linus/master acme/perf/core v6.11-rc5]
> [If your patch is applied to the wrong git tree, kindly drop us a note.
> And when submitting patch, we suggest to use '--base' as documented in
> https://git-scm.com/docs/git-format-patch#_base_tree_information]
>
> url: https://github.com/intel-lab-lkp/linux/commits/Andrii-Nakryiko/uprobes-revamp-uprobe-refcounting-and-lifetime-management/20240830-024135
> base: tip/perf/core
> patch link: https://lore.kernel.org/r/20240829183741.3331213-9-andrii%40kernel.org
> patch subject: [PATCH v4 8/8] uprobes: switch to RCU Tasks Trace flavor for better performance
> config: i386-buildonly-randconfig-004-20240830 (https://download.01.org/0day-ci/archive/20240831/202408310130.t9EBKteQ-lkp@intel.com/config)
> compiler: clang version 18.1.5 (https://github.com/llvm/llvm-project 617a15a9eac96088ae5e9134248d8236e34b91b1)
> reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20240831/202408310130.t9EBKteQ-lkp@intel.com/reproduce)
>
> If you fix the issue in a separate patch/commit (i.e. not just a new version of
> the same patch/commit), kindly add following tags
> | Reported-by: kernel test robot <lkp@intel.com>
> | Closes: https://lore.kernel.org/oe-kbuild-all/202408310130.t9EBKteQ-lkp@intel.com/
>
> All errors (new ones prefixed by >>):
>
> >> kernel/events/uprobes.c:1157:2: error: call to undeclared function 'synchronize_rcu_tasks_trace'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]
> 1157 | synchronize_rcu_tasks_trace();
> | ^
> kernel/events/uprobes.c:1157:2: note: did you mean 'synchronize_rcu_tasks_rude'?
> include/linux/rcupdate.h:206:6: note: 'synchronize_rcu_tasks_rude' declared here
> 206 | void synchronize_rcu_tasks_rude(void);
> | ^
> 1 error generated.
Missing #include <linux/rcupdate_trace.h>, will add.
>
>
> vim +/synchronize_rcu_tasks_trace +1157 kernel/events/uprobes.c
>
> 1145
> 1146 void uprobe_unregister_sync(void)
> 1147 {
> 1148 /*
> 1149 * Now that handler_chain() and handle_uretprobe_chain() iterate over
> 1150 * uprobe->consumers list under RCU protection without holding
> 1151 * uprobe->register_rwsem, we need to wait for RCU grace period to
> 1152 * make sure that we can't call into just unregistered
> 1153 * uprobe_consumer's callbacks anymore. If we don't do that, fast and
> 1154 * unlucky enough caller can free consumer's memory and cause
> 1155 * handler_chain() or handle_uretprobe_chain() to do an use-after-free.
> 1156 */
> > 1157 synchronize_rcu_tasks_trace();
> 1158 }
> 1159 EXPORT_SYMBOL_GPL(uprobe_unregister_sync);
> 1160
>
> --
> 0-DAY CI Kernel Test Service
> https://github.com/intel/lkp-tests/wiki
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