On Mon, Jul 15, 2024 at 10:10 AM Andrii Nakryiko
[off-list ref] wrote:

On Mon, Jul 15, 2024 at 7:45 AM Peter Zijlstra [off-list ref] wrote:

quoted

On Thu, Jul 11, 2024 at 09:57:44PM -0700, Andrii Nakryiko wrote:

quoted

But then I also ran it on Linux built from perf/uprobes branch (these
patches), and after a few seconds I see that there is no more
attachment/detachment happening. Eventually I got splats, which you
can see in [1]. I used `sudo ./uprobe-stress -a10 -t5 -m5 -f3` command
to run it inside my QEMU image.

So them git voodoo incantations did work and I got it built. I'm running
that exact same line above (minus the sudo, because test box only has a
root account I think) on real hardware.

I'm now ~100 periods in and wondering what 'eventually' means...

So I was running in a qemu set up with 16 cores on top of bare metal's
80 core CPU (Intel(R) Xeon(R) Gold 6138 CPU @ 2.00GHz). I just tried
it again, and I can reproduce it within first few periods:

WORKING HARD!..

PERIOD #1 STATS:
FUNC CALLS               919632
UPROBE HITS              706351
URETPROBE HITS           641679
ATTACHED LINKS              951
ATTACHED UPROBES           2421
ATTACHED URETPROBES        2343
MMAP CALLS                33533
FORKS CALLS                 241

PERIOD #2 STATS:
FUNC CALLS                11444
UPROBE HITS               14320
URETPROBE HITS             9896
ATTACHED LINKS               26
ATTACHED UPROBES             75
ATTACHED URETPROBES          61
MMAP CALLS                39093
FORKS CALLS                  14

PERIOD #3 STATS:
FUNC CALLS                  230
UPROBE HITS                 152
URETPROBE HITS              145
ATTACHED LINKS                2
ATTACHED UPROBES              2
ATTACHED URETPROBES           2
MMAP CALLS                39121
FORKS CALLS                   0

PERIOD #4 STATS:
FUNC CALLS                    0
UPROBE HITS                   0
URETPROBE HITS                0
ATTACHED LINKS                0
ATTACHED UPROBES              0
ATTACHED URETPROBES           0
MMAP CALLS                39010
FORKS CALLS                   0

You can see in the second period all the numbers drop and by period #4
(which is about 20 seconds in) anything but mmap()ing stops. When I
said "eventually" I meant about a minute tops, however long it takes
to do soft lockup detection, 23 seconds this time.

So it should be very fast.

Note that I'm running with debug kernel configuration (see [0] for
full kernel config), here are debug-related settings, in case that
makes a difference:

$ cat ~/linux-build/default/.config | rg -i debug | rg -v '^#'
CONFIG_X86_DEBUGCTLMSR=y
CONFIG_ARCH_SUPPORTS_DEBUG_PAGEALLOC=y
CONFIG_BLK_DEBUG_FS=y
CONFIG_PNP_DEBUG_MESSAGES=y
CONFIG_AIC7XXX_DEBUG_MASK=0
CONFIG_AIC79XX_DEBUG_MASK=0
CONFIG_SCSI_MVSAS_DEBUG=y
CONFIG_DM_DEBUG=y
CONFIG_MLX4_DEBUG=y
CONFIG_USB_SERIAL_DEBUG=m
CONFIG_INFINIBAND_MTHCA_DEBUG=y
CONFIG_INFINIBAND_IPOIB_DEBUG=y
CONFIG_INFINIBAND_IPOIB_DEBUG_DATA=y
CONFIG_CIFS_DEBUG=y
CONFIG_DLM_DEBUG=y
CONFIG_DEBUG_BUGVERBOSE=y
CONFIG_DEBUG_KERNEL=y
CONFIG_DEBUG_INFO=y
CONFIG_DEBUG_INFO_DWARF4=y
CONFIG_DEBUG_INFO_COMPRESSED_NONE=y
CONFIG_DEBUG_INFO_BTF=y
CONFIG_DEBUG_INFO_BTF_MODULES=y
CONFIG_DEBUG_FS=y
CONFIG_DEBUG_FS_ALLOW_ALL=y
CONFIG_ARCH_HAS_DEBUG_WX=y
CONFIG_HAVE_DEBUG_KMEMLEAK=y
CONFIG_ARCH_HAS_DEBUG_VM_PGTABLE=y
CONFIG_ARCH_HAS_DEBUG_VIRTUAL=y
CONFIG_SCHED_DEBUG=y
CONFIG_DEBUG_PREEMPT=y
CONFIG_LOCK_DEBUGGING_SUPPORT=y
CONFIG_DEBUG_RT_MUTEXES=y
CONFIG_DEBUG_SPINLOCK=y
CONFIG_DEBUG_MUTEXES=y
CONFIG_DEBUG_WW_MUTEX_SLOWPATH=y
CONFIG_DEBUG_RWSEMS=y
CONFIG_DEBUG_LOCK_ALLOC=y
CONFIG_DEBUG_LOCKDEP=y
CONFIG_DEBUG_ATOMIC_SLEEP=y
CONFIG_DEBUG_IRQFLAGS=y
CONFIG_X86_DEBUG_FPU=y
CONFIG_FAULT_INJECTION_DEBUG_FS=y

  [0] https://gist.github.com/anakryiko/97a023a95b30fb0fe607ff743433e64b

quoted

Also, this is a 2 socket, 10 core per socket, 2 threads per core
ivybridge thing, are those parameters sufficient?

Should be, I guess? It might be VM vs bare metal differences, though.
I'll try to run this on bare metal with more production-like kernel
configuration to see if I can still trigger this. Will let you know
the results when I get them.

Ok, so I ran it on bare metal host with production config. I didn't
really bother to specify parameters (so just one thread for
everything, the default):

# ./uprobe-stress
WORKING HARD!..

PERIOD #1 STATS:
FUNC CALLS              2959843
UPROBE HITS             1001312
URETPROBE HITS                0
ATTACHED LINKS                6
ATTACHED UPROBES             28
ATTACHED URETPROBES           0
MMAP CALLS                 8143
FORKS CALLS                 301

PERIOD #2 STATS:
FUNC CALLS                    0
UPROBE HITS              822826
URETPROBE HITS                0
ATTACHED LINKS                0
ATTACHED UPROBES              0
ATTACHED URETPROBES           0
MMAP CALLS                 8006
FORKS CALLS                 270

PERIOD #3 STATS:
FUNC CALLS                    0
UPROBE HITS              889534
URETPROBE HITS                0
ATTACHED LINKS                0
ATTACHED UPROBES              0
ATTACHED URETPROBES           0
MMAP CALLS                 8004
FORKS CALLS                 288

PERIOD #4 STATS:
FUNC CALLS                    0
UPROBE HITS              886506
URETPROBE HITS                0
ATTACHED LINKS                0
ATTACHED UPROBES              0
ATTACHED URETPROBES           0
MMAP CALLS                 8120
FORKS CALLS                 285

PERIOD #5 STATS:
FUNC CALLS                    0
UPROBE HITS              804556
URETPROBE HITS                0
ATTACHED LINKS                0
ATTACHED UPROBES              0
ATTACHED URETPROBES           0
MMAP CALLS                 7131
FORKS CALLS                 263
^C
EXITING...

Message from syslogd@kerneltest003.10.atn6.facebook.com at Jul 15 11:06:33 ...
 kernel:[ 2194.334618] watchdog: BUG: soft lockup - CPU#71 stuck for
48s! [uprobe-stress:69900]

It was weird on the very first period (no uretprobes, small amount of
attachments). And sure enough (gmail will reformat below in the
garbage, so [0] has the splat with the original formatting).

  [0] https://gist.github.com/anakryiko/3e3ddcccc5ea3ca70ce90b5491485fdc

I also keep getting:

Message from syslogd@kerneltest003.10.atn6.facebook.com at Jul 15 11:09:41 ...
 kernel:[ 2382.334088] watchdog: BUG: soft lockup - CPU#71 stuck for
223s! [uprobe-stress:69900]

so it's not just a temporary slowdown


[ 2166.893057] rcu: INFO: rcu_sched self-detected stall on CPU
[ 2166.904199] rcu:     71-....: (20999 ticks this GP)
idle=2c84/1/0x4000000000000000 softirq=30158/30158 fqs=8110
[ 2166.923810] rcu:              hardirqs   softirqs   csw/system
[ 2166.934939] rcu:      number:        0        183            0
[ 2166.946064] rcu:     cputime:       60          0        10438
==> 10549(ms)
[ 2166.959969] rcu:     (t=21065 jiffies g=369217 q=207850 ncpus=80)
[ 2166.971619] CPU: 71 PID: 69900 Comm: uprobe-stress Tainted: G S
     E      6.10.0-rc7-00071-g9423ae8ef6ff #62
[ 2166.992275] Hardware name: Quanta Tioga Pass Single Side
01-0032211004/Tioga Pass Single Side, BIOS F08_3A24 05/13/2020
[ 2167.013804] RIP: 0010:uprobe_notify_resume+0x622/0xe20
[ 2167.024064] Code: 8d 9d c0 00 00 00 48 89 df 4c 89 e6 e8 d7 f9 ff
ff 84 c0 0f 85 c6 06 00 00 48 89 5c 24 20 41 8b 6d 58 40 f6 c5 01 74
23 f3 90 <eb> f2 83 7c 24 18 00 48 8b 44 24 10 0f 8e 71 01 00 00 bf 05
00 00
[ 2167.061543] RSP: 0000:ffffc9004a49fe78 EFLAGS: 00000202
[ 2167.071973] RAX: 0000000000000000 RBX: ffff88a11d307fc0 RCX: ffff88a120752c40
[ 2167.086223] RDX: 00000000000042ec RSI: ffffc9004a49ff58 RDI: ffff88a11d307fc0
[ 2167.100472] RBP: 0000000000000003 R08: ffff88a12516e500 R09: ffff88a12516f208
[ 2167.114717] R10: 00000000004042ec R11: 000000000000000f R12: ffffc9004a49ff58
[ 2167.128967] R13: ffff88a11d307f00 R14: 00000000004042ec R15: ffff88a09042e000
[ 2167.143213] FS:  00007fd252000640(0000) GS:ffff88bfffbc0000(0000)
knlGS:0000000000000000
[ 2167.159368] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 2167.170843] CR2: 00007fd244000b60 CR3: 000000209090b001 CR4: 00000000007706f0
[ 2167.185091] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[ 2167.199340] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[ 2167.213586] PKRU: 55555554
[ 2167.218994] Call Trace:
[ 2167.223883]  <IRQ>
[ 2167.227905]  ? rcu_dump_cpu_stacks+0x77/0xd0
[ 2167.236433]  ? print_cpu_stall+0x150/0x2a0
[ 2167.244615]  ? rcu_sched_clock_irq+0x319/0x490
[ 2167.253487]  ? update_process_times+0x71/0xa0
[ 2167.262191]  ? tick_nohz_handler+0xc0/0x100
[ 2167.270544]  ? tick_setup_sched_timer+0x170/0x170
[ 2167.279937]  ? __hrtimer_run_queues+0xe3/0x250
[ 2167.288815]  ? hrtimer_interrupt+0xf0/0x390
[ 2167.297168]  ? __sysvec_apic_timer_interrupt+0x47/0x110
[ 2167.307602]  ? sysvec_apic_timer_interrupt+0x68/0x80
[ 2167.317519]  </IRQ>
[ 2167.321710]  <TASK>
[ 2167.325905]  ? asm_sysvec_apic_timer_interrupt+0x16/0x20
[ 2167.336517]  ? uprobe_notify_resume+0x622/0xe20
[ 2167.345565]  ? uprobe_notify_resume+0x609/0xe20
[ 2167.354612]  ? __se_sys_futex+0xf3/0x180
[ 2167.362445]  ? arch_uprobe_exception_notify+0x29/0x40
[ 2167.372533]  ? notify_die+0x51/0xb0
[ 2167.379503]  irqentry_exit_to_user_mode+0x7f/0xd0
[ 2167.388896]  asm_exc_int3+0x35/0x40
[ 2167.395862] RIP: 0033:0x4042ec
[ 2167.401966] Code: fc 8b 45 fc 89 c7 e8 6f 07 00 00 83 c0 01 c9 c3
cc 48 89 e5 48 83 ec 10 89 7d fc 8b 45 fc 89 c7 e8 55 07 00 00 83 c0
01 c9 c3 <cc> 48 89 e5 48 83 ec 10 89 7d fc 8b 45 fc 89 c7 e8 3b 07 00
00 83
[ 2167.439439] RSP: 002b:00007fd251fff8a8 EFLAGS: 00000206
[ 2167.449874] RAX: 00000000004042ec RBX: 00007fd252000640 RCX: 000000000000001c
[ 2167.464122] RDX: 0000000000000033 RSI: 0000000000000064 RDI: 0000000000000033
[ 2167.478368] RBP: 00007fd251fff8d0 R08: 00007fd2523fa234 R09: 00007fd2523fa280
[ 2167.492617] R10: 0000000000000000 R11: 0000000000000246 R12: 00007fd252000640
[ 2167.506866] R13: 0000000000000016 R14: 00007fd252289930 R15: 0000000000000000
[ 2167.521117]  </TASK>