Stuff Michael Meeks is doing
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This is my (in)activity log. You might like to visit my employer
Novell which is an amazing company, and also
Dell who in days of yore provided me with a
free laptop for Gnome development / conferences.
Also if you have the time to read this sort of stuff you could enlighten
yourself by going to Unraveling Wittgenstein's net or if
you are feeling objectionable perhaps here.
Older items:
2008: (
J
F
M
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J
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2007: (
J
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J
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2006,
2005,
2004,
2003,
2002,
2001,
2000,
1999,
legacy html
- Up early, J. off to the dentist, back to poking at relocations
on writer start (from LD_DEBUG=bindings output):
| variant | startup bindings |
|---|
| current | 91300 |
|---|
| -Bsymbolic-functions | 63600 |
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| -Bsym + vtrelocs | 58100 |
|---|
Clearly there are a number of PLT/function bindings that
we're not saving on startup. Browsing the remaining relocations I
was rather amused to find 2400 relocations on startup (4%) are to
please a cunning 31337 'memory-saving' strategy: the thinking goes like this:
- Instead of having lots of small strings in-line in
several libraries, lets have a single copy of each string in a
common library (svtools). [ so far, so clever ].
- Lets implement that using a symbol per string eg.
extern SVT_DLLPUBLIC sal_Char const SVTOOLS_CONSTASCII_DECL( sHTML_S_aacute, "aacute" );
[ oh dear ! - this of course generates a nice const char * rodata
string - but it also generates another string in the svtools symbol
table: "sHTML_S_aacute", plus another string in -each- shared library that
refers to it ].
So - comparing to the approach of using a simple in-line string
(also uniquified by any decent compiler & put in rodata), we loose
size: ( sizeof "sHTML_S_" + sizeof (relocation) ) * ( num-references + 1 )
and we loose performance: 2400 unique named relocations, searched across 50+
shared libraries: ~0.8% of OO.o CPU time on startup. And all in the name of
efficiency. Unfortunately, the technique dates back to the dawn of
time, (in cvs history terms), so it's hard to discern the intention. I wonder
where else it's used.
Anyhow, the 'best' fix (to save the optimisation) is to export
one symbol, s_HTML_Strings that is an enumerated array of strings
#define sHTML_S_aacute s_HTML_Strings[eHTML_S_aAcute]
type
thing. But for now, some search/replace action is perhaps easier.
- Spammed the suse gcc team with my patches for comment, poked
at Sankar's first iogrind patch - nice. Dug at mail, investigated generating
live memory snapshots for running processes, ie. a simple core-dump to run
'strings' on, to try to work out how XYZ process managed to blow up the
heap so comprehensively. Unfortunately, it's not easy
/proc/<pid>/mem
looks like just what you want, until you try to use it - you have to
pread the addresses out. Dug at
cryopid for some stealable code, before giving up. Presumably manual
fun and dump binary memory filename start_addr end_addr
in gdb is the best that can be done easily.
- Huge 24inch screen arrived, got that setup - albeit the Mobility
FireGL 5200 insists on flickering when you type (or move the mouse -
interesting), then got SL10.3 installed on the AMD UVC prototype, now it
has it's own screen: great to get a USB image booted and a (remote) network
install done in a couple of hours. Amazon ordering frenzy, bed.
In case it's not painfully obvious: the reflections reflected here are my
own; mine, all mine ! and don't reflect the views of Novell, The
Lithuanian Gov't or Arnold Schwarzenegger. It's also important to
realise that I'm not in on the Swedish Conspiracy.
Occasionally people ask for formal photos for conferences,
bio.
or fun.
Michael Meeks (michael.meeks@novell.com)
