Hi Brendan,
Thanks for the data.
On 04/13/2015 10:49 PM, Brendan Gregg wrote:
G'Day Hemant,
Thanks for testing; here's how I compiled node.js:
# apt-get install -y systemtap-sdt-dev # provides "dtrace"
# git clone --depth 1 https://github.com/joyent/node
# cd node
# ./configure --with-dtrace
# make
Thanks, I was able to see the error in my case too.
Will look into this as to why its failing to record on these using perf
record -e "%node:gc__done", even after it creates an entry into the
uprobe_events file :
# cat /sys/kernel/debug/tracing/uprobe_events
p:node/gc__done /home/hemant/node/out/Release/node:0x000000000081d354
node readelf:
# readelf -n node
Notes at offset 0x00000254 with length 0x00000020:
Owner Data size Description
GNU 0x00000010 NT_GNU_ABI_TAG (ABI version tag)
OS: Linux, ABI: 2.6.24
Notes at offset 0x00000274 with length 0x00000024:
Owner Data size Description
GNU 0x00000014 NT_GNU_BUILD_ID (unique build ID
bitstring)
Build ID: 85dd5ef00ffde124f220b94c8a2b552d9274a89f
Notes at offset 0x00c45fd8 with length 0x000004e4:
Owner Data size Description
stapsdt 0x0000003c NT_STAPSDT (SystemTap probe descriptors)
Provider: node
Name: gc__start
Location: 0x0000000000bf7894, Base: 0x0000000000f252de, Semaphore:
0x0000000001245fa8
Arguments: 4@%esi 4@%edx 8@%rdi
stapsdt 0x0000003a NT_STAPSDT (SystemTap probe descriptors)
Provider: node
Name: gcstart
Location: 0x0000000000bf7895, Base: 0x0000000000f252de, Semaphore:
0x0000000001245faa
Arguments: 4@%esi 4@%edx 8@%rdi
stapsdt 0x0000003b NT_STAPSDT (SystemTap probe descriptors)
Provider: node
Name: gc__done
Location: 0x0000000000bf78a4, Base: 0x0000000000f252de, Semaphore:
0x0000000001245fac
Arguments: 4@%esi 4@%edx 8@%rdi
stapsdt 0x0000005c NT_STAPSDT (SystemTap probe descriptors)
[...etc...]
(the "gcstart" probe is one I added to test the underscore theory.)
On a separate issue, all the SDT markers here are using semaphore. And
there is no support for markers with semaphores currently. Here is some
old discussion on this:
https://sourceware.org/ml/systemtap/2013-q3/msg00236.html
We need to discuss this issue in more detail and find out a way to
support those too.
So, even if the error wasn't being shown with the current patchset, perf
wouldn't record any hit on the markers.
Here's also the event files:
# ls /sys/kernel/debug/tracing/events/node/
enable gc__start_11 gc__start_2 gcstart_5 http__server__request
filter gcstart_1_1 gcstart_2 gc__start_6 http__server__request_1
gcstart gc__start_12 gc__start_3 gcstart_6 http__server__request_2
gc__start gc__start_13 gcstart_3 gc__start_7 http__server__request_3
gc__start_1 gc__start_14 gc__start_4 gcstart_7 http__server__request_4
gcstart_1 gc__start_15 gcstart_4 gc__start_8 net__server__connection
gc__start_10 gc__start_16 gc__start_5 gc__start_9 net__server__connection_1
This is after several iterations of --add and --del. Something seems
to be going wrong there. Thanks,
This is because perf is able to make an entry into the uprobe_events
file, but since its throwing an error just after this, its not deleting
that entry from the uprobe_events (which will delete the corresponding
events from /sys/kernel/debug/tracing/events/node too).
Will certainly look into this.
[SNIP]
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--
Thanks,
Hemant Kumar
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