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Date: Tue, 8 Mar 2016 18:24:25 +0100 From: Ingo Molnar <mingo@...nel.org> To: Dmitry Vyukov <dvyukov@...gle.com> Cc: Peter Zijlstra <peterz@...radead.org>, Wang Nan <wangnan0@...wei.com>, Ingo Molnar <mingo@...hat.com>, LKML <linux-kernel@...r.kernel.org>, He Kuang <hekuang@...wei.com>, Alexei Starovoitov <ast@...nel.org>, Arnaldo Carvalho de Melo <acme@...hat.com>, Brendan Gregg <brendan.d.gregg@...il.com>, Jiri Olsa <jolsa@...nel.org>, Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>, Namhyung Kim <namhyung@...nel.org>, Zefan Li <lizefan@...wei.com>, pi3orama@....com Subject: Re: [RESEND PATCH 0/5] perf core: Support overwrite ring buffer * Dmitry Vyukov <dvyukov@...gle.com> wrote: > On Tue, Mar 8, 2016 at 5:48 PM, Ingo Molnar <mingo@...nel.org> wrote: > > > > * Ingo Molnar <mingo@...nel.org> wrote: > > > >> It only had a couple of seconds of runtime: > >> > >> 49652 mingo 20 0 1434276 52144 11344 S 0.0 0.0 0:00.54 syz-manager > >> 49661 mingo 20 0 2196672 43948 10448 S 0.0 0.0 0:05.59 syz-fuzzer > > > > Ah, so it appears to making some progress: > > > > 49652 mingo 20 0 1581740 47600 11344 S 0.0 0.0 0:00.58 syz-manager > > 49661 mingo 20 0 2204868 43720 10448 S 0.0 0.0 0:07.49 syz-fuzzer > > > > 49652 mingo 20 0 1598132 31512 11344 S 0.0 0.0 0:00.61 syz-manager > > 49661 mingo 20 0 2204868 44252 10448 S 0.0 0.0 0:09.09 syz-fuzzer > > > > but only about +1 second runtime added every minute or so. Is that expected? > > The main work is done by child syz-executor processes. Hm, they don't seem to be doing anything: fomalhaut:~> ps aux | grep syz-executor mingo 41506 0.0 0.0 0 0 pts/2 Z+ 18:19 0:00 [syz-executor] <defunct> mingo 41509 0.0 0.0 0 0 pts/2 Z+ 18:19 0:00 [syz-executor] <defunct> mingo 41513 0.0 0.0 0 0 pts/2 Z+ 18:19 0:00 [syz-executor] <defunct> mingo 41515 0.0 0.0 0 0 pts/2 Z+ 18:19 0:00 [syz-executor] <defunct> mingo 41523 0.0 0.0 0 0 pts/2 Z+ 18:19 0:00 [syz-executor] <defunct> mingo 41601 0.0 0.0 0 0 pts/2 Z+ 18:19 0:00 [syz-executor] <defunct> mingo 41608 0.0 0.0 0 0 pts/2 Z+ 18:19 0:00 [syz-executor] <defunct> mingo 41662 0.0 0.0 0 0 pts/2 Z+ 18:19 0:00 [syz-executor] <defunct> mingo 41764 0.0 0.0 0 0 pts/2 Z+ 18:19 0:00 [syz-executor] <defunct> mingo 41966 0.0 0.0 0 0 pts/2 Z+ 18:19 0:00 [syz-executor] <defunct> mingo 42029 0.0 0.0 0 0 pts/2 Z+ 18:19 0:00 [syz-executor] <defunct> mingo 42084 0.0 0.0 0 0 pts/2 Z+ 18:19 0:00 [syz-executor] <defunct> mingo 42145 0.0 0.0 0 0 pts/2 Z+ 18:19 0:00 [syz-executor] <defunct> mingo 42149 0.0 0.0 0 0 pts/2 Z+ 18:19 0:00 [syz-executor] <defunct> mingo 42166 0.0 0.0 0 0 pts/2 Z+ 18:19 0:00 [syz-executor] <defunct> mingo 42175 0.0 0.0 0 0 pts/2 Z+ 18:19 0:00 [syz-executor] <defunct> mingo 57627 2.2 0.0 1860540 44884 pts/2 Sl+ 18:16 0:04 /home/mingo/go/src/github.com/google/syzkaller/workdir/instance-0/syz-fuzzer -executor /home/mingo/go/src/github.com/google/syzkaller/workdir/instance-0/syz-executor -name local-0 -manager 127.0.0.1:33809 -output=none -procs 16 -leak=false -cover=false -nobody=true -v 0 ... because they are recycling: fomalhaut:~> ps aux | grep syz-executor mingo 57627 1.6 0.0 1942468 44624 pts/2 Sl+ 18:16 0:05 /home/mingo/go/src/github.com/google/syzkaller/workdir/instance-0/syz-fuzzer -executor /home/mingo/go/src/github.com/google/syzkaller/workdir/instance-0/syz-executor -name local-0 -manager 127.0.0.1:33809 -output=none -procs 16 -leak=false -cover=false -nobody=true -v 0 mingo 98448 0.0 0.0 0 0 pts/2 Z+ 18:21 0:00 [syz-executor] <defunct> mingo 98454 0.0 0.0 0 0 pts/2 Z+ 18:21 0:00 [syz-executor] <defunct> mingo 98468 0.0 0.0 0 0 pts/2 Z+ 18:21 0:00 [syz-executor] <defunct> mingo 98472 0.0 0.0 0 0 pts/2 Z+ 18:21 0:00 [syz-executor] <defunct> mingo 98476 0.0 0.0 0 0 pts/2 Z+ 18:21 0:00 [syz-executor] <defunct> mingo 98522 0.0 0.0 0 0 pts/2 Z+ 18:21 0:00 [syz-executor] <defunct> mingo 98525 0.0 0.0 0 0 pts/2 Z+ 18:21 0:00 [syz-executor] <defunct> mingo 98548 0.0 0.0 0 0 pts/2 Z+ 18:21 0:00 [syz-executor] <defunct> mingo 98568 0.0 0.0 0 0 pts/2 Z+ 18:21 0:00 [syz-executor] <defunct> mingo 98596 0.0 0.0 0 0 pts/2 Z+ 18:21 0:00 [syz-executor] <defunct> mingo 98618 0.0 0.0 0 0 pts/2 Z+ 18:21 0:00 [syz-executor] <defunct> mingo 98644 0.0 0.0 0 0 pts/2 Z+ 18:21 0:00 [syz-executor] <defunct> mingo 98695 0.0 0.0 0 0 pts/2 Z+ 18:21 0:00 [syz-executor] <defunct> mingo 98708 0.0 0.0 0 0 pts/2 Z+ 18:21 0:00 [syz-executor] <defunct> mingo 98737 0.0 0.0 0 0 pts/2 Z+ 18:21 0:00 [syz-executor] <defunct> mingo 98756 0.0 0.0 0 0 pts/2 Z+ 18:21 0:00 [syz-executor] <defunct> I'm not seeing anything happen in 'top' - only a mostly idle system. > syz-manager/syz-fuzzer only guide the process. > You can set "procs" param in config to higher value to increase CPU > utilization. To get more bugs you want to saturate all CPUs to trigger > more unusual thread interleavings. So right now it doesn't seem to saturate 16 CPUs - not even close to it. > If there is a second unfinished thread hanging on a kernel spinlock or > mutex, then it's definitely bad. > It also helps to enable CONFIG_RCU_STALL_COMMON=y, > CONFIG_DEBUG_ATOMIC_SLEEP=y, CONFIG_WQ_WATCHDOG=y and spinlock/mutex > debugging. These can detect various stalls. I can just Ctrl-C the manager and it shuts down within a few seconds: 2016/03/08 17:39:25 serving rpc on tcp://127.0.0.1:33809 2016/03/08 17:51:45 local-0: lost connection: exit status 2 2016/03/08 17:51:45 local-0: saving crash 'lost connection' to crash-local-0-1457455905403390570 2016/03/08 18:04:04 local-0: lost connection: exit status 2 2016/03/08 18:04:04 local-0: saving crash 'lost connection' to crash-local-0-1457456644779165131 2016/03/08 18:16:24 local-0: lost connection: exit status 2 2016/03/08 18:16:24 local-0: saving crash 'lost connection' to crash-local-0-1457457384707190124 ^C2016/03/08 18:22:53 shutting down... with nothing hanging around: fomalhaut:~/go/src/github.com/google/syzkaller> ps aux | grep -i syz mingo 1374 0.0 0.0 118476 2376 pts/2 S+ 18:23 0:00 grep --color=auto -i syz and with no kernel messages in dmesg - and with a fully functional system. I'm running the 16-task load on a 120 CPU system - should I increase it to 120? Does the code expect to saturate the system? Thanks, Ingo
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