Linux: Swap Pre-Fetching

Con Kolivas [interview] posted a patch for the 2.6.13 kernel [story] that implements cache prefetching. The patch is based onearlier work by Thomas Schlichter. Con explains, "I have resuscitated and rewritten some early prefetch code Thomas Schlichter did in late 2.5 to create a configurable kernel thread that reads in swap from ram in reverse order it was written out. It does this once kswapd has been idle for a minute (implying no current vm stress)." He goes on to explain, "Note that swapped in pages are kept on backing store (swap), meaning no further I/O is required if the page needs to swap back out."

Con noted that the patch will be included in his next -ck patchset [story], however, he also posted it to the lkml to guage interest in eventually merging the effort into the mainline kernel, and to encourage greater testing and feedback.