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authorJeremy Fitzhardinge <jeremy@goop.org>2009-02-27 13:25:21 -0800
committerIngo Molnar <mingo@elte.hu>2009-03-02 12:07:48 +0100
commitdb949bba3c7cf2e664ac12e237c6d4c914f0c69d (patch)
tree4de65831dd1de95f642bed15bc9788edd74c48da /arch/x86/include
parent645af4e9e0e32481e3336dda813688732c7e5f0f (diff)
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 <jeremy.fitzhardinge@citrix.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'arch/x86/include')
-rw-r--r--arch/x86/include/asm/processor.h6
1 files changed, 0 insertions, 6 deletions
diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h
index c7a98f73821..76139506c3e 100644
--- a/arch/x86/include/asm/processor.h
+++ b/arch/x86/include/asm/processor.h
@@ -248,7 +248,6 @@ struct x86_hw_tss {
#define IO_BITMAP_LONGS (IO_BITMAP_BYTES/sizeof(long))
#define IO_BITMAP_OFFSET offsetof(struct tss_struct, io_bitmap)
#define INVALID_IO_BITMAP_OFFSET 0x8000
-#define INVALID_IO_BITMAP_OFFSET_LAZY 0x9000
struct tss_struct {
/*
@@ -263,11 +262,6 @@ struct tss_struct {
* be within the limit.
*/
unsigned long io_bitmap[IO_BITMAP_LONGS + 1];
- /*
- * Cache the current maximum and the last task that used the bitmap:
- */
- unsigned long io_bitmap_max;
- struct thread_struct *io_bitmap_owner;
/*
* .. and then another 0x100 bytes for the emergency kernel stack: