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Feature #570
closedlttng-tools 2.2.0-rc2: enable-channel man pages ought to mention minimum sub-buffer sizes
Start date:
06/25/2013
Due date:
% Done:
0%
Estimated time:
Description
It seems the minimum size of the LTTng sub-buffers is 4096 bytes (for either domain and either buffering scheme):
$ sudo -H lttng create s Session s created. Traces will be written in /root/lttng-traces/s-20130625-101152 $ sudo -H lttng enable-channel k1 -k --subbuf-size 131072 Kernel channel k1 enabled for session s $ sudo -H lttng enable-channel k2 -k --subbuf-size 65536 Kernel channel k2 enabled for session s $ sudo -H lttng enable-channel k3 -k --subbuf-size 32768 Kernel channel k3 enabled for session s $ sudo -H lttng enable-channel k4 -k --subbuf-size 16384 Kernel channel k4 enabled for session s $ sudo -H lttng enable-channel k5 -k --subbuf-size 8192 Kernel channel k5 enabled for session s $ sudo -H lttng enable-channel k6 -k --subbuf-size 4096 Kernel channel k6 enabled for session s $ sudo -H lttng enable-channel k7 -k --subbuf-size 2048 PERROR [20531/20631]: ioctl kernel create channel: Invalid argument (in kernel_create_channel() at kernel.c:144) Error: Channel k7: Kernel create channel failed (session s) Warning: Some command(s) went wrong
$ sudo -H lttng create ss Session ss created. Traces will be written in /root/lttng-traces/ss-20130625-101446 $ sudo -H lttng enable-channel k7 -k --subbuf-size 2048 PERROR [20531/20631]: ioctl kernel create channel: Invalid argument (in kernel_create_channel() at kernel.c:144) Error: Channel k7: Kernel create channel failed (session ss) Warning: Some command(s) went wrong $ sudo -H lttng enable-channel u7 -u --subbuf-size 2048 Error: Channel u7: Invalid parameter (session ss) Warning: Some command(s) went wrong $ sudo -H lttng enable-channel u6 -u --subbuf-size 4096 UST channel u6 enabled for session ss
This should be mentioned in the man pages.
Updated by David Goulet over 11 years ago
Unfortunately, this varies on the system. The page size is used to be the
minimum possible.
However, we can mention that and a way to find out like using
- getconf PAGESIZE
Once I'm able to log in, I'll switch that to 2.2 target and in Bug.
Thanks!
Updated by David Goulet over 10 years ago
- Status changed from New to Resolved
- Target version set to 2.3
Currently fixed in 2.3.
--subbuf-size SIZE Subbuffer size in bytes {+k,+M,+G}. (default UST uid: 131072, UST pid: 4096, kernel: 262144, metadata: 4096) Rounded up to the next power of 2. The minimum subbuffer size, for each tracer, is the max value between the default above and the system page size. You can issue this command to get the current page size on your system: $ getconf PAGE_SIZE
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