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Smoke and mirrors: monitoring function calls that do not exist anymore

During investigating I ran once again into statistics in the Oracle database that still provide a useful details, but the actual naming of the statistic is describing a situation that in reality does not exist anymore. The statistics I am talking about are ‘calls to kcmgcs’, ‘calls to kcmgrs’, ‘calls to kcmgas’ and ‘calls to get snapshot scn: kcmgss’.

Disclaimer: this is research. Any of these techniques potentially can crash your instance or leave your database in a corrupted state. Test the techniques used in this article severely before applying it in an actual situation. Use at your own risk.

Back to the ‘calls to’ statistics. To see what I mean here, you can look up the functions in symbol table in the Oracle executable. There are several ways to do that, one way is using gdb:

Introducing stapflame, extended stack profiling using systemtap, perf and flame graphs

There’s been a lot of work in the area of profiling. One of the things I have recently fallen in love with is Brendan Gregg’s flamegraphs. I work mainly on Linux, which means I use perf for generating stack traces. Luca Canali put a lot of effort in generating extended stack profiling methods, including kernel (only) stack traces and CPU state, reading the wait interface via direct SGA reading and kernel stack traces and getting userspace stack traces using libunwind and ptrace plus kernel stack and CPU state. I was inspired by the last method, but wanted more information, like process CPU state including runqueue time.

November/December Highlights

In the Oracle technical universe, it seems that the end of the calendar year is always eventful. First there’s OpenWorld: obviously significant for official announcements and insight into Oracle’s strategy. It’s also the week when many top engineers around the world meet up in San Francisco to catch up over beers – justifying hotel and flight expenses by preparing technical presentations of their most interesting and recent problems or projects. UKOUG and DOAG happen shortly after OpenWorld with a similar (but more European) impact – and December seems to mingle the domino effect of tweets and blog posts inspired by the conference social activity with holiday anticipation at work.

I avoided any conference trips this year but I still noticed the usual surge in interesting twitter and blog activity. It seems worthwhile to record a few highlights of the past two months as the year wraps up.

November/December Highlights

In the Oracle technical universe, it seems that the end of the calendar year is always eventful. First there’s OpenWorld: obviously significant for official announcements and insight into Oracle’s strategy. It’s also the week when many top engineers around the world meet up in San Francisco to catch up over beers – justifying hotel and flight expenses by preparing technical presentations of their most interesting and recent problems or projects. UKOUG and DOAG happen shortly after OpenWorld with a similar (but more European) impact – and December seems to mingle the domino effect of tweets and blog posts inspired by the conference social activity with holiday anticipation at work.

I avoided any conference trips this year but I still noticed the usual surge in interesting twitter and blog activity. It seems worthwhile to record a few highlights of the past two months as the year wraps up.

November/December Highlights

In the Oracle technical universe, it seems that the end of the calendar year is always eventful. First there’s OpenWorld: obviously significant for official announcements and insight into Oracle’s strategy. It’s also the week when many top engineers around the world meet up in San Francisco to catch up over beers – justifying hotel and flight expenses by preparing technical presentations of their most interesting and recent problems or projects. UKOUG and DOAG happen shortly after OpenWorld with a similar (but more European) impact – and December seems to mingle the domino effect of tweets and blog posts inspired by the conference social activity with holiday anticipation at work.

I avoided any conference trips this year but I still noticed the usual surge in interesting twitter and blog activity. It seems worthwhile to record a few highlights of the past two months as the year wraps up.

November/December Highlights

In the Oracle technical universe, it seems that the end of the calendar year is always eventful. First there’s OpenWorld: obviously significant for official announcements and insight into Oracle’s strategy. It’s also the week when many top engineers around the world meet up in San Francisco to catch up over beers – justifying hotel and flight expenses by preparing technical presentations of their most interesting and recent problems or projects. UKOUG and DOAG happen shortly after OpenWorld with a similar (but more European) impact – and December seems to mingle the domino effect of tweets and blog posts inspired by the conference social activity with holiday anticipation at work.

I avoided any conference trips this year but I still noticed the usual surge in interesting twitter and blog activity. It seems worthwhile to record a few highlights of the past two months as the year wraps up.

November/December Highlights

In the Oracle technical universe, it seems that the end of the calendar year is always eventful. First there’s OpenWorld: obviously significant for official announcements and insight into Oracle’s strategy. It’s also the week when many top engineers around the world meet up in San Francisco to catch up over beers – justifying hotel and flight expenses by preparing technical presentations of their most interesting and recent problems or projects. UKOUG and DOAG happen shortly after OpenWorld with a similar (but more European) impact – and December seems to mingle the domino effect of tweets and blog posts inspired by the conference social activity with holiday anticipation at work.

I avoided any conference trips this year but I still noticed the usual surge in interesting twitter and blog activity. It seems worthwhile to record a few highlights of the past two months as the year wraps up.

November/December Highlights

In the Oracle technical universe, it seems that the end of the calendar year is always eventful. First there’s OpenWorld: obviously significant for official announcements and insight into Oracle’s strategy. It’s also the week when many top engineers around the world meet up in San Francisco to catch up over beers – justifying hotel and flight expenses by preparing technical presentations of their most interesting and recent problems or projects. UKOUG and DOAG happen shortly after OpenWorld with a similar (but more European) impact – and December seems to mingle the domino effect of tweets and blog posts inspired by the conference social activity with holiday anticipation at work.

I avoided any conference trips this year but I still noticed the usual surge in interesting twitter and blog activity. It seems worthwhile to record a few highlights of the past two months as the year wraps up.

Describing Performance Improvements (Beware of Ratios)

Recently, I received into my Spam folder an ad claiming that a product could “...improve performance 1000%.” Claims in that format have bugged me for a long time, at least as far back as the 1990s, when some of the most popular Oracle “tips & techniques” books of the era used that format a lot to state claims.

Beware of claims worded like that.

Whenever I see “...improve performance 1000%,” I have to do extra work to decode what the author has encoded in his tidy numerical package with a percent-sign bow. The two performance improvement formulas that make sense to me are these: