On Wed, 10 Apr 2024 11:38:11 +0100 Jonthan Haslam <jonathan.haslam@xxxxxxxxx> wrote: > Hi Masami, > > > > > Which is why I was asking to land this patch as is, as it relieves the > > > > scalability pains in production and is easy to backport to old > > > > kernels. And then we can work on batched APIs and switch to per-CPU rw > > > > semaphore. > > > > OK, then I'll push this to for-next at this moment. > > Please share if you have a good idea for the batch interface which can be > > backported. I guess it should involve updating userspace changes too. > > Did you (or anyone else) need anything more from me on this one so that it > can be pushed? I provided some benchmark numbers but happy to provide > anything else that may be required. Yeah, if you can update with the result, it looks better to me. Or, can I update the description? Thank you, > > Thanks! > > Jon. > > > > > Thank you! > > > > > > > > > > So I hope you can reconsider and accept improvements in this patch, > > > > while Jonathan will keep working on even better final solution. > > > > Thanks! > > > > > > > > > I look forward to your formalized results :) > > > > > > > > > > > BTW, as part of BPF selftests, we have a multi-attach test for uprobes > > > and USDTs, reporting attach/detach timings: > > > $ sudo ./test_progs -v -t uprobe_multi_test/bench > > > bpf_testmod.ko is already unloaded. > > > Loading bpf_testmod.ko... > > > Successfully loaded bpf_testmod.ko. > > > test_bench_attach_uprobe:PASS:uprobe_multi_bench__open_and_load 0 nsec > > > test_bench_attach_uprobe:PASS:uprobe_multi_bench__attach 0 nsec > > > test_bench_attach_uprobe:PASS:uprobes_count 0 nsec > > > test_bench_attach_uprobe: attached in 0.120s > > > test_bench_attach_uprobe: detached in 0.092s > > > #400/5 uprobe_multi_test/bench_uprobe:OK > > > test_bench_attach_usdt:PASS:uprobe_multi__open 0 nsec > > > test_bench_attach_usdt:PASS:bpf_program__attach_usdt 0 nsec > > > test_bench_attach_usdt:PASS:usdt_count 0 nsec > > > test_bench_attach_usdt: attached in 0.124s > > > test_bench_attach_usdt: detached in 0.064s > > > #400/6 uprobe_multi_test/bench_usdt:OK > > > #400 uprobe_multi_test:OK > > > Summary: 1/2 PASSED, 0 SKIPPED, 0 FAILED > > > Successfully unloaded bpf_testmod.ko. > > > > > > So it should be easy for Jonathan to validate his changes with this. > > > > > > > > Thank you, > > > > > > > > > > > > > > > > > Jon. > > > > > > > > > > > > > > > > > > > > Thank you, > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > BTW, how did you measure the overhead? I think spinlock overhead > > > > > > > > > will depend on how much lock contention happens. > > > > > > > > > > > > > > > > > > Thank you, > > > > > > > > > > > > > > > > > > > > > > > > > > > > > [0] https://docs.kernel.org/locking/spinlocks.html > > > > > > > > > > > > > > > > > > > > Signed-off-by: Jonathan Haslam <jonathan.haslam@xxxxxxxxx> > > > > > > > > > > --- > > > > > > > > > > kernel/events/uprobes.c | 22 +++++++++++----------- > > > > > > > > > > 1 file changed, 11 insertions(+), 11 deletions(-) > > > > > > > > > > > > > > > > > > > > diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c > > > > > > > > > > index 929e98c62965..42bf9b6e8bc0 100644 > > > > > > > > > > --- a/kernel/events/uprobes.c > > > > > > > > > > +++ b/kernel/events/uprobes.c > > > > > > > > > > @@ -39,7 +39,7 @@ static struct rb_root uprobes_tree = RB_ROOT; > > > > > > > > > > */ > > > > > > > > > > #define no_uprobe_events() RB_EMPTY_ROOT(&uprobes_tree) > > > > > > > > > > > > > > > > > > > > -static DEFINE_SPINLOCK(uprobes_treelock); /* serialize rbtree access */ > > > > > > > > > > +static DEFINE_RWLOCK(uprobes_treelock); /* serialize rbtree access */ > > > > > > > > > > > > > > > > > > > > #define UPROBES_HASH_SZ 13 > > > > > > > > > > /* serialize uprobe->pending_list */ > > > > > > > > > > @@ -669,9 +669,9 @@ static struct uprobe *find_uprobe(struct inode *inode, loff_t offset) > > > > > > > > > > { > > > > > > > > > > struct uprobe *uprobe; > > > > > > > > > > > > > > > > > > > > - spin_lock(&uprobes_treelock); > > > > > > > > > > + read_lock(&uprobes_treelock); > > > > > > > > > > uprobe = __find_uprobe(inode, offset); > > > > > > > > > > - spin_unlock(&uprobes_treelock); > > > > > > > > > > + read_unlock(&uprobes_treelock); > > > > > > > > > > > > > > > > > > > > return uprobe; > > > > > > > > > > } > > > > > > > > > > @@ -701,9 +701,9 @@ static struct uprobe *insert_uprobe(struct uprobe *uprobe) > > > > > > > > > > { > > > > > > > > > > struct uprobe *u; > > > > > > > > > > > > > > > > > > > > - spin_lock(&uprobes_treelock); > > > > > > > > > > + write_lock(&uprobes_treelock); > > > > > > > > > > u = __insert_uprobe(uprobe); > > > > > > > > > > - spin_unlock(&uprobes_treelock); > > > > > > > > > > + write_unlock(&uprobes_treelock); > > > > > > > > > > > > > > > > > > > > return u; > > > > > > > > > > } > > > > > > > > > > @@ -935,9 +935,9 @@ static void delete_uprobe(struct uprobe *uprobe) > > > > > > > > > > if (WARN_ON(!uprobe_is_active(uprobe))) > > > > > > > > > > return; > > > > > > > > > > > > > > > > > > > > - spin_lock(&uprobes_treelock); > > > > > > > > > > + write_lock(&uprobes_treelock); > > > > > > > > > > rb_erase(&uprobe->rb_node, &uprobes_tree); > > > > > > > > > > - spin_unlock(&uprobes_treelock); > > > > > > > > > > + write_unlock(&uprobes_treelock); > > > > > > > > > > RB_CLEAR_NODE(&uprobe->rb_node); /* for uprobe_is_active() */ > > > > > > > > > > put_uprobe(uprobe); > > > > > > > > > > } > > > > > > > > > > @@ -1298,7 +1298,7 @@ static void build_probe_list(struct inode *inode, > > > > > > > > > > min = vaddr_to_offset(vma, start); > > > > > > > > > > max = min + (end - start) - 1; > > > > > > > > > > > > > > > > > > > > - spin_lock(&uprobes_treelock); > > > > > > > > > > + read_lock(&uprobes_treelock); > > > > > > > > > > n = find_node_in_range(inode, min, max); > > > > > > > > > > if (n) { > > > > > > > > > > for (t = n; t; t = rb_prev(t)) { > > > > > > > > > > @@ -1316,7 +1316,7 @@ static void build_probe_list(struct inode *inode, > > > > > > > > > > get_uprobe(u); > > > > > > > > > > } > > > > > > > > > > } > > > > > > > > > > - spin_unlock(&uprobes_treelock); > > > > > > > > > > + read_unlock(&uprobes_treelock); > > > > > > > > > > } > > > > > > > > > > > > > > > > > > > > /* @vma contains reference counter, not the probed instruction. */ > > > > > > > > > > @@ -1407,9 +1407,9 @@ vma_has_uprobes(struct vm_area_struct *vma, unsigned long start, unsigned long e > > > > > > > > > > min = vaddr_to_offset(vma, start); > > > > > > > > > > max = min + (end - start) - 1; > > > > > > > > > > > > > > > > > > > > - spin_lock(&uprobes_treelock); > > > > > > > > > > + read_lock(&uprobes_treelock); > > > > > > > > > > n = find_node_in_range(inode, min, max); > > > > > > > > > > - spin_unlock(&uprobes_treelock); > > > > > > > > > > + read_unlock(&uprobes_treelock); > > > > > > > > > > > > > > > > > > > > return !!n; > > > > > > > > > > } > > > > > > > > > > -- > > > > > > > > > > 2.43.0 > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > -- > > > > > > > > > Masami Hiramatsu (Google) <mhiramat@xxxxxxxxxx> > > > > > > > > > > > > > > > > > > > > > -- > > > > > > > Masami Hiramatsu (Google) <mhiramat@xxxxxxxxxx> > > > > > > > > > > > > > > > -- > > > > > Masami Hiramatsu (Google) <mhiramat@xxxxxxxxxx> > > > > > > -- > > Masami Hiramatsu (Google) <mhiramat@xxxxxxxxxx> -- Masami Hiramatsu (Google) <mhiramat@xxxxxxxxxx>
