On Tue, 10 Sep 2024 10:43:12 -0700 Andrii Nakryiko <[email protected]> wrote:
> 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. > > We also select TASKS_TRACE_RCU for UPROBES in Kconfig due to the new > dependency. > Looks good to me. Peter, do you have any comment? Reviewed-by: Masami Hiramatsu (Google) <[email protected]> > Reviewed-by: Oleg Nesterov <[email protected]> > Signed-off-by: Andrii Nakryiko <[email protected]> > --- > 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 > -- Masami Hiramatsu (Google) <[email protected]>
