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authorLinus Torvalds <torvalds@linux-foundation.org>2016-03-15 18:23:56 +0100
committerLinus Torvalds <torvalds@linux-foundation.org>2016-03-15 18:23:56 +0100
commitecc026bff6e8444c6b50dcde192e7acdaf42bf82 (patch)
treee2a3ac4aab57a84147684cbd0992df9a61c2eca3 /arch/x86/kernel/fpu/init.c
parentMerge branch 'x86-build-for-linus' of git://git.kernel.org/pub/scm/linux/kern... (diff)
parentMerge branch 'linus' into x86/fpu, to pick up fixes (diff)
downloadlinux-ecc026bff6e8444c6b50dcde192e7acdaf42bf82.tar.xz
linux-ecc026bff6e8444c6b50dcde192e7acdaf42bf82.zip
Merge branch 'x86-fpu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull x86 fpu updates from Ingo Molnar: "The biggest change in terms of impact is the changing of the FPU context switch model to 'eagerfpu' for all CPU types, via: commit 58122bf1d856: "x86/fpu: Default eagerfpu=on on all CPUs" This makes all FPU saves and restores synchronous and makes the FPU code a lot more obvious to read. In the next cycle, if this change is problem free, we'll remove the old lazy FPU restore code altogether. This change flushed out some old bugs, which should all be fixed by now, BYMMV" * 'x86-fpu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: x86/fpu: Default eagerfpu=on on all CPUs x86/fpu: Speed up lazy FPU restores slightly x86/fpu: Fold fpu_copy() into fpu__copy() x86/fpu: Fix FNSAVE usage in eagerfpu mode x86/fpu: Fix math emulation in eager fpu mode
Diffstat (limited to 'arch/x86/kernel/fpu/init.c')
-rw-r--r--arch/x86/kernel/fpu/init.c13
1 files changed, 5 insertions, 8 deletions
diff --git a/arch/x86/kernel/fpu/init.c b/arch/x86/kernel/fpu/init.c
index bd08fb77073d..54c86fffbf9f 100644
--- a/arch/x86/kernel/fpu/init.c
+++ b/arch/x86/kernel/fpu/init.c
@@ -262,7 +262,10 @@ static void __init fpu__init_system_xstate_size_legacy(void)
* not only saved the restores along the way, but we also have the
* FPU ready to be used for the original task.
*
- * 'eager' switching is used on modern CPUs, there we switch the FPU
+ * 'lazy' is deprecated because it's almost never a performance win
+ * and it's much more complicated than 'eager'.
+ *
+ * 'eager' switching is by default on all CPUs, there we switch the FPU
* state during every context switch, regardless of whether the task
* has used FPU instructions in that time slice or not. This is done
* because modern FPU context saving instructions are able to optimize
@@ -273,7 +276,7 @@ static void __init fpu__init_system_xstate_size_legacy(void)
* to use 'eager' restores, if we detect that a task is using the FPU
* frequently. See the fpu->counter logic in fpu/internal.h for that. ]
*/
-static enum { AUTO, ENABLE, DISABLE } eagerfpu = AUTO;
+static enum { ENABLE, DISABLE } eagerfpu = ENABLE;
/*
* Find supported xfeatures based on cpu features and command-line input.
@@ -344,15 +347,9 @@ static void __init fpu__init_system_ctx_switch(void)
*/
static void __init fpu__init_parse_early_param(void)
{
- /*
- * No need to check "eagerfpu=auto" again, since it is the
- * initial default.
- */
if (cmdline_find_option_bool(boot_command_line, "eagerfpu=off")) {
eagerfpu = DISABLE;
fpu__clear_eager_fpu_features();
- } else if (cmdline_find_option_bool(boot_command_line, "eagerfpu=on")) {
- eagerfpu = ENABLE;
}
if (cmdline_find_option_bool(boot_command_line, "no387"))