Messages in this thread | | | Subject | Re: [PATCH v5 00/10] tracing: 'hist' triggers | From | Tom Zanussi <> | Date | Thu, 21 May 2015 10:26:29 -0500 |
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Hi Masami,
On Thu, 2015-05-21 at 17:08 +0900, Masami Hiramatsu wrote: > Hi Tom, > > On 2015/05/21 6:19, Tom Zanussi wrote: > > This is v5 of the 'hist triggers' patchset, following feedback from > > v4. > > > > Changes from v4: > > > > This version addresses some problems and suggestions made by Daniel > > Wagner - a lot of the code was reworked to get rid of the distinction > > between keys and values, and as a result, both keys and values can be > > used as sort keys. As suggested, it also allows 'val=' to be absent > > in a trigger command - if no 'val' is specified, hitcount is assumed > > and automatically used as the only val. > > Thank you for this amazing work! :) > Here is an example how I've used it.
Nice example - thanks for sharing it!
> > --------- > [root@localhost perf]# ./perf probe -a '__kmalloc caller=$stack0 size' > Added new event: > probe:__kmalloc (on __kmalloc with caller=$stack0 size) > > You can now use it in all perf tools, such as: > > perf record -e probe:__kmalloc -aR sleep 1 > > [root@localhost perf]# cd /sys/kernel/debug/tracing > [root@localhost tracing]# echo hist:keys=caller.sym > events/probe/__kmalloc/trigger > [root@localhost tracing]# echo 1 > events/probe/__kmalloc/enable > [root@localhost tracing]# cat events/probe/__kmalloc/hist > # trigger info: hist:keys=caller.sym:vals=hitcount:sort=hitcount:size=2048 [active] > > caller: [ffffffff811964d7] tracing_map_sort_entries hitcount: 1 > caller: [ffffffff81296120] load_elf_binary hitcount: 1 > caller: [ffffffff813eb98c] context_struct_to_string hitcount: 1 > caller: [ffffffff81264c8c] simple_xattr_alloc hitcount: 1 > caller: [ffffffff811e0a02] shmem_initxattrs hitcount: 1 > caller: [ffffffff81295eb6] load_elf_phdrs hitcount: 2 > caller: [ffffffff8169c49b] sk_prot_alloc hitcount: 2 > caller: [ffffffff81395567] kmem_alloc hitcount: 6 > caller: [ffffffff8125b844] alloc_fdmem hitcount: 6 > caller: [ffffffff81415918] bio_alloc_bioset hitcount: 8 > caller: [ffffffff813ecc44] security_context_to_sid_core hitcount: 17 > caller: [ffffffff812621bb] seq_buf_alloc hitcount: 18 > > Totals: > Hits: 64 > Entries: 12 > Dropped: 0 > ---------- > Good! Just one more, I also want to see the offset of the symbols. :) >
Sure, I could add a new 'sym-offset' modifier e.g. caller.sym-offset, or I can just have .sym always include the offset.
> And this can dig deeper to investigate the size histogram, with filtering by caller. > ---------- > [root@localhost tracing]# echo \!hist:keys=caller.sym > events/probe/__kmalloc/trigger > [root@localhost tracing]# echo hist:keys=size if caller==0xffffffff812621bb > events/probe/__kmalloc/trigger > [root@localhost tracing]# cat events/probe/__kmalloc/hist > # trigger info: hist:keys=size:vals=hitcount:sort=hitcount:size=2048 if caller==0xffffffff812621bb [active] > > size: 3024 hitcount: 1 > size: 4096 hitcount: 12 > > Totals: > Hits: 13 > Entries: 2 > Dropped: 0 > [root@localhost tracing]# > --------- > Yes! This interactivity is what I want :) > > Another enhancement ideas what I want are here: > - Named hist instance, which can be shared among several events. > Since probing an inlined function can make a several probe-events, > those need to share a histogram among them.
Makes sense - any ideas on how this would work from an interface perspective?
Would just allowing hist="myname": ... suffice? i.e. creating a hist trigger with hist="myname" would look for an existing trigger with that name - if found would use that, otherwise create a new instance with that name...
> - Multiple hist instances for each event, which allows us to compare > several histograms which have different filters. >
Yeah, that would be a nice enhancement - will do that when I get a chance.
> Anyway, without above, this look fine to me :)
Great.
> > > > The map code was also separated out into a separate file, > > tracing_map.c, allowing it to be reused. It also adds a second tracer > > called function_hist that actually does reuse the code, as an RFC > > patch. > > > > Patch 01/10 [tracing: Update cond flag when enabling or disabling..] > > is a fix for a problem noticed by Daniel and that fixes a problem in > > existing trigger code and should be applied regardless of whether the > > rest of the patchset is merged. > > I've reviewed that. >
Thanks for doing that.
> > As mentioned, patch 10/10 is an RFC patch implementing a new tracer > > based on the function tracer code. It's a fun little tool and is > > useful for a specific problem I'm working on (and is also a nice test > > of the tracing_map code), but is an RFC because first, I'm not sure it > > would really be of general interest and secondly, it's POC-level > > quality and I'd need to spend more time fixing it up to make it > > upstreamable, but I don't want to waste my time if not. > > BTW, I've hit a warning while testing: > > [ 8431.319668] ------------[ cut here ]------------ > [ 8431.319678] WARNING: CPU: 0 PID: 14413 at /home/mhiramat/ksrc/linux-3/kernel/trace/ftrace.c:5080 ftrace_init_array_ops+0x6e/0x90() > [ 8431.319680] Modules linked in: xt_CHECKSUM iptable_mangle ipt_MASQUERADE nf_nat_masquerade_ipv4 iptable_nat nf_nat_ipv4 nf_nat nf_conntrack_ipv4 nf_defrag_ipv4 xt_conntrack nf_conntrack ipt_REJECT > nf_reject_ipv4 iptable_filter ip_tables tun bridge stp llc coretemp crct10dif_pclmul crc32_pclmul crc32c_intel ghash_clmulni_intel aesni_intel glue_helper lrw gf128mul ablk_helper cryptd iTCO_wdt > iTCO_vendor_support ipmi_si lpc_ich ipmi_msghandler mfd_core pcspkr i2c_i801 i2c_ismt shpchp acpi_cpufreq uinput sr_mod sd_mod cdrom ast syscopyarea sysfillrect sysimgblt drm_kms_helper ttm drm ahci > igb libahci libata ptp pps_core dca i2c_algo_bit i2c_core dm_mirror dm_region_hash dm_log dm_mod > [ 8431.319736] CPU: 0 PID: 14413 Comm: ftracetest Not tainted 4.1.0-rc3+ #33 > [ 8431.319738] Hardware name: Supermicro A1SAi/A1SAi, BIOS 1.0b 11/06/2013 > [ 8431.319741] 0000000000000000 0000000037d828fa ffff880467eabc98 ffffffff817d5b48 > [ 8431.319745] 0000000000000000 0000000000000000 ffff880467eabcd8 ffffffff810c70ba > [ 8431.319748] ffff880467eabcb8 ffffffff820a2b80 ffffffff81197330 ffffffff820a2b80 > [ 8431.319752] Call Trace: > [ 8431.319760] [<ffffffff817d5b48>] dump_stack+0x45/0x57 > [ 8431.319765] [<ffffffff810c70ba>] warn_slowpath_common+0x8a/0xc0 > [ 8431.319769] [<ffffffff81197330>] ? function_hist_open+0x20/0x20 > [ 8431.319772] [<ffffffff810c71ea>] warn_slowpath_null+0x1a/0x20 > [ 8431.319776] [<ffffffff81183efe>] ftrace_init_array_ops+0x6e/0x90 > [ 8431.319779] [<ffffffff811976d8>] function_hist_init+0x28/0x160 > [ 8431.319783] [<ffffffff811918ee>] tracing_set_tracer+0x10e/0x1b0 > [ 8431.319787] [<ffffffff8137cd8f>] ? xfs_file_buffered_aio_write+0xaf/0x240 > [ 8431.319791] [<ffffffff81191bc0>] tracing_set_trace_write+0x90/0xd0 > [ 8431.319796] [<ffffffff8123d2d7>] __vfs_write+0x37/0x110 > [ 8431.319799] [<ffffffff81240198>] ? __sb_start_write+0x58/0x100 > [ 8431.319804] [<ffffffff813d5393>] ? security_file_permission+0x23/0xa0 > [ 8431.319808] [<ffffffff8123da09>] vfs_write+0xa9/0x1b0 > [ 8431.319812] [<ffffffff810716fc>] ? do_audit_syscall_entry+0x6c/0x70 > [ 8431.319816] [<ffffffff8123e8b5>] SyS_write+0x55/0xd0 > [ 8431.319821] [<ffffffff817dd26e>] system_call_fastpath+0x12/0x71 > [ 8431.319823] ---[ end trace 7f402f6ea6c9516c ]--- > [ 8431.319826] ftrace ops had function_hist_call+0x0/0x150 for function > > Here is the ftrace.c:5080 > ----- > void ftrace_init_array_ops(struct trace_array *tr, ftrace_func_t func) > { > /* If we filter on pids, update to use the pid function */ > if (tr->flags & TRACE_ARRAY_FL_GLOBAL) { > if (WARN_ON(tr->ops->func != ftrace_stub)) <-- here > printk("ftrace ops had %pS for function\n", > tr->ops->func); > /* Only the top level instance does pid tracing */ > if (!list_empty(&ftrace_pids)) { > set_ftrace_pid_function(func); > func = ftrace_pid_func; > } > } > tr->ops->func = func; > tr->ops->private = tr; > } > ----- > > Since function_hist_call was introduced by 10/10, this warning was also > occurred by it. >
Right, why it's an RFC ;-) I need to look some more at the ftrace code and figure out how to hook it up properly...
Thanks,
Tom
> Thank you, > > >
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