| Message ID | 20240829183741.3331213-1-andrii@kernel.org (mailing list archive) |
|---|---|
| Headers | show |
| Series | uprobes: RCU-protected hot path optimizations | expand |
On 08/29, Andrii Nakryiko wrote: > > v3->v4: > - added back consumer_rwsem into consumer_del(), which was accidentally > omitted earlier (Jiri); still, Reviewed-by: Oleg Nesterov <oleg@redhat.com>
On Fri, Aug 30, 2024 at 12:24:01PM +0200, Oleg Nesterov wrote: > On 08/29, Andrii Nakryiko wrote: > > > > v3->v4: > > - added back consumer_rwsem into consumer_del(), which was accidentally > > omitted earlier (Jiri); > > still, > > Reviewed-by: Oleg Nesterov <oleg@redhat.com> > Let me go queue this in perf/core then. Thanks!
On 09/03, Peter Zijlstra wrote: > > On Fri, Aug 30, 2024 at 12:24:01PM +0200, Oleg Nesterov wrote: > > On 08/29, Andrii Nakryiko wrote: > > > > > > v3->v4: > > > - added back consumer_rwsem into consumer_del(), which was accidentally > > > omitted earlier (Jiri); > > > > still, > > > > Reviewed-by: Oleg Nesterov <oleg@redhat.com> > > > > Let me go queue this in perf/core then. Thanks! FYI, Andrii was going to send another revision due to missing include inux/rcupdate_trace.h in kernel/events/uprobes.c. See the build failure reported kernel test robot: https://lore.kernel.org/all/202408310130.t9EBKteQ-lkp@intel.com/ Oleg.
On Tue, Sep 03, 2024 at 03:59:43PM +0200, Oleg Nesterov wrote: > On 09/03, Peter Zijlstra wrote: > > > > On Fri, Aug 30, 2024 at 12:24:01PM +0200, Oleg Nesterov wrote: > > > On 08/29, Andrii Nakryiko wrote: > > > > > > > > v3->v4: > > > > - added back consumer_rwsem into consumer_del(), which was accidentally > > > > omitted earlier (Jiri); > > > > > > still, > > > > > > Reviewed-by: Oleg Nesterov <oleg@redhat.com> > > > > > > > Let me go queue this in perf/core then. Thanks! > > FYI, Andrii was going to send another revision due to missing include > inux/rcupdate_trace.h in kernel/events/uprobes.c. > > See the build failure reported kernel test robot: > https://lore.kernel.org/all/202408310130.t9EBKteQ-lkp@intel.com/ No problem, I'll sit on it.
This patch set is heavily inspired by Peter Zijlstra's uprobe optimization patches ([0]) and continues that work, albeit trying to keep complexity to the minimum, and attepting to reuse existing primitives as much as possible. The goal here is to optimize common uprobe triggering hot path, while keeping the rest of locking mostly intact. I've added uprobe_unregister_sync() into the error handling code path inside uprobe_unregister(). This is due to recent refactorings from Oleg Nesterov ([1]), which necessitates this addition. Except for refcounting change patch (which I stongly believe is a good improvement we should do and forget about quasi-refcounting schema of uprobe->consumers list), the rest of the changes are similar to Peter's initial changes in [0]. Main differences would be: - no special RCU protection for mmap and fork handling, we just stick to refcounts there, as those are infrequent and not a performance-sensitive code path, while being complex and thus benefiting from proper locking; - the above means we don't need to do any custom SRCU additions to handle forking code path; - I handled UPROBE_HANDLER_REMOVE problem in handler_chain() differently, again, leveraging existing locking scheam; - I kept refcount usage for uretprobe and single-stepping uprobes, I plan to address that in a separate follow up patches. The plan is to avoid task_work with a lockless atomic xchg()/cmpxchg()-based solution; - finally, I dutifully was using SRCU throughout all the changes, and only last patch switches SRCU to RCU Tasks Trace and demonstrates significant performance and scalability gains from this. The changes in this patch set were tested using BPF selftests and using uprobe-stress ([2]) tool. Now, for the benchmarking results. I've used the following script (which utilizes BPF selftests-based bench tool). The CPU used was 80-core Intel Xeon Gold 6138 CPU @ 2.00GHz running kernel with production-like config. I minimized background noise by stopping any service I could identify and stop, so results are pretty stable and variability is pretty small, overall. Benchmark script: #!/bin/bash set -eufo pipefail for i in uprobe-nop uretprobe-nop; do for p in 1 2 4 8 16 32 64; do summary=$(sudo ./bench -w3 -d5 -p$p -a trig-$i | tail -n1) total=$(echo "$summary" | cut -d'(' -f1 | cut -d' ' -f3-) percpu=$(echo "$summary" | cut -d'(' -f2 | cut -d')' -f1 | cut -d'/' -f1) printf "%-15s (%2d cpus): %s (%s/s/cpu)\n" $i $p "$total" "$percpu" done echo done With all the lock-avoiding changes done in this patch set, we get a pretty decent improvement in performance and scalability of uprobes with number of CPUs, even though we are still nowhere near linear scalability. This is due to the remaining mmap_lock, which is currently taken to resolve interrupt address to inode+offset and then uprobe instance. And, of course, uretprobes still need similar RCU to avoid refcount in the hot path, which will be addressed in the follow up patches. BASELINE (on top of Oleg's clean up patches) ============================================ uprobe-nop ( 1 cpus): 3.032 ± 0.023M/s ( 3.032M/s/cpu) uprobe-nop ( 2 cpus): 3.452 ± 0.005M/s ( 1.726M/s/cpu) uprobe-nop ( 4 cpus): 3.663 ± 0.005M/s ( 0.916M/s/cpu) uprobe-nop ( 8 cpus): 3.718 ± 0.038M/s ( 0.465M/s/cpu) uprobe-nop (16 cpus): 3.344 ± 0.008M/s ( 0.209M/s/cpu) uprobe-nop (32 cpus): 2.288 ± 0.021M/s ( 0.071M/s/cpu) uprobe-nop (64 cpus): 3.205 ± 0.004M/s ( 0.050M/s/cpu) uretprobe-nop ( 1 cpus): 1.979 ± 0.005M/s ( 1.979M/s/cpu) uretprobe-nop ( 2 cpus): 2.361 ± 0.005M/s ( 1.180M/s/cpu) uretprobe-nop ( 4 cpus): 2.309 ± 0.002M/s ( 0.577M/s/cpu) uretprobe-nop ( 8 cpus): 2.253 ± 0.001M/s ( 0.282M/s/cpu) uretprobe-nop (16 cpus): 2.007 ± 0.000M/s ( 0.125M/s/cpu) uretprobe-nop (32 cpus): 1.624 ± 0.003M/s ( 0.051M/s/cpu) uretprobe-nop (64 cpus): 2.149 ± 0.001M/s ( 0.034M/s/cpu) Up to second-to-last patch (i.e., SRCU-based optimizations) =========================================================== 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) For baseline vs SRCU, peak througput increased from 3.7 M/s (million uprobe triggerings per second) up to about 8 M/s. For uretprobes it's a bit more modest with bump from 2.4 M/s to 5 M/s. For SRCU vs RCU Tasks Trace, peak throughput for uprobes increases further from 8 M/s to 10.3 M/s (+28%!), and for uretprobes from 5.3 M/s to 5.8 M/s (+11%), as we have more work to do on uretprobes side. Even single-thread (no contention) performance is slightly better: 3.276 M/s to 3.396 M/s (+3.5%) for uprobes, and 2.055 M/s to 2.174 M/s (+5.8%) for uretprobes. [0] https://lore.kernel.org/linux-trace-kernel/20240711110235.098009979@infradead.org/ [1] https://lore.kernel.org/linux-trace-kernel/20240729134444.GA12293@redhat.com/ [2] https://github.com/libbpf/libbpf-bootstrap/tree/uprobe-stress v3->v4: - added back consumer_rwsem into consumer_del(), which was accidentally omitted earlier (Jiri); - left out RFC patches, we can continue discussion on v3 patch set, if necessary; v2->v3: - undid rcu and rb_node fields colocation which were causing crashes (Oleg); - ensure synchronize_srcu() on registration failure in patch #4 (Oleg); v1->v2: - added back missed kfree() in patch #1 (Oleg); - forgot the rest, but there were a few small things here and there. Andrii Nakryiko (6): uprobes: revamp uprobe refcounting and lifetime management uprobes: protected uprobe lifetime with SRCU uprobes: get rid of enum uprobe_filter_ctx in uprobe filter callbacks uprobes: travers uprobe's consumer list locklessly under SRCU protection uprobes: perform lockless SRCU-protected uprobes_tree lookup uprobes: switch to RCU Tasks Trace flavor for better performance Peter Zijlstra (2): perf/uprobe: split uprobe_unregister() rbtree: provide rb_find_rcu() / rb_find_add_rcu() include/linux/rbtree.h | 67 +++ include/linux/uprobes.h | 20 +- kernel/events/uprobes.c | 391 +++++++++++------- kernel/trace/bpf_trace.c | 8 +- kernel/trace/trace_uprobe.c | 15 +- .../selftests/bpf/bpf_testmod/bpf_testmod.c | 3 +- 6 files changed, 321 insertions(+), 183 deletions(-)