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Feature #13178

::msgbuf could see more than 8KB of logs

Added by Joshua M. Clulow about 1 month ago. Updated about 1 month ago.

Status:
New
Priority:
Normal
Assignee:
Category:
kernel
Start date:
Due date:
% Done:

0%

Estimated time:
Difficulty:
Bite-size
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Description

The ::msgbuf dcmd in MDB can be very useful for debugging the state of a machine leading up to a crash dump. The messages it reads are stored in a STREAMS data queue, log_recentq, with a high water mark of LOG_RECENTSIZE -- presently 8KB.

At this stage, the budget for memory here probably extends to at least, say, 64KB. This would provide eight times more kernel log context in a crash dump.

#1

Updated by Nick Ewins about 1 month ago

  • Assignee set to Nick Ewins
#2

Updated by Nick Ewins about 1 month ago

Tested by using ::msgbuf dcmd in MDB. Generated and read crash dumps, before and after the change.

#3

Updated by Joshua M. Clulow about 1 month ago

Might be worth confirming that roughly the expected number of bytes come out, as well as just that it still works; e.g., via, say:

odin # mdb -k
Loading modules: [ unix genunix ... ]
> ::msgbuf ! wc -c
    7947

(NB: this system has been up for months, and has thus generated a bunch of log messages already. You might need to induce some to be generated for testing!)

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