From: Jeremy Fitzhardinge Date: Fri, 27 Feb 2009 21:25:21 +0000 (-0800) Subject: x86-32: use non-lazy io bitmap context switching X-Git-Tag: v2.6.30-rc1~211^2~26^5~2 X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=db949bba3c7cf2e664ac12e237c6d4c914f0c69d;p=pandora-kernel.git x86-32: use non-lazy io bitmap context switching Impact: remove 32-bit optimization to prepare unification x86-32 and -64 differ in the way they context-switch tasks with io permission bitmaps. x86-64 simply copies the next tasks io bitmap into place (if any) on context switch. x86-32 invalidates the bitmap on context switch, so that the next IO instruction will fault; at that point it installs the appropriate IO bitmap. This makes context switching IO-bitmap-using tasks a bit more less expensive, at the cost of making the next IO instruction slower due to the extra fault. This tradeoff only makes sense if IO-bitmap-using processes are relatively common, but they don't actually use IO instructions very often. However, in a typical desktop system, the only process likely to be using IO bitmaps is the X server, and nothing at all on a server. Therefore the lazy context switch doesn't really win all that much, and its just a gratuitious difference from 64-bit code. This patch removes the lazy context switch, with a view to unifying this code in a later change. Signed-off-by: Jeremy Fitzhardinge Signed-off-by: Ingo Molnar --- Reading git-diff-tree failed