Threads in the new ISO C Standard from 2011
Threads in the new ISO C Standard from 2011
Threads in the new ISO C Standard from 2011
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Implementation on a specific architecture: Power.<br />
Illustrations of what actually is ordered for several situations.<br />
We will beg<strong>in</strong> with <strong>the</strong> Power synchronization <strong>in</strong>structions.<br />
Approximate clock counts below are not fixed but depends on what is<br />
happen<strong>in</strong>g <strong>in</strong> <strong>the</strong> mach<strong>in</strong>e at <strong>the</strong> moment.<br />
Numbers <strong>from</strong> Christoph von Praun: ”Deconstruct<strong>in</strong>g Redundant<br />
Memory Synchronization” (while at IBM Research).<br />
mnemonic name Power4 cycles Power5 cycles<br />
ldarw/stwxc. load and reserve / store conditional 80 75<br />
hwsync or sync heavy weight sync 140 50<br />
lwsync light weight sync 110 25<br />
isync <strong>in</strong>struction sync 30 10<br />
eieio enforce <strong>in</strong>order execution of I/O not measured not measured<br />
We want to use functions which use <strong>the</strong> less costly <strong>in</strong>structions!<br />
Such as <strong>the</strong> consume operation which is only an ord<strong>in</strong>ary load<br />
<strong>in</strong>struction on Power!<br />
Jonas Skeppstedt (js@cs.lth.se) Lecture 6 2013 46 / 70