diff options
Diffstat (limited to 'arch/x86/include/asm/fpu/types.h')
| -rw-r--r-- | arch/x86/include/asm/fpu/types.h | 34 |
1 files changed, 0 insertions, 34 deletions
diff --git a/arch/x86/include/asm/fpu/types.h b/arch/x86/include/asm/fpu/types.h index 48df486b02f9..3c80f5b9c09d 100644 --- a/arch/x86/include/asm/fpu/types.h +++ b/arch/x86/include/asm/fpu/types.h @@ -322,17 +322,6 @@ struct fpu { unsigned char fpregs_active; /* - * @counter: - * - * This counter contains the number of consecutive context switches - * during which the FPU stays used. If this is over a threshold, the - * lazy FPU restore logic becomes eager, to save the trap overhead. - * This is an unsigned char so that after 256 iterations the counter - * wraps and the context switch behavior turns lazy again; this is to - * deal with bursty apps that only use the FPU for a short time: - */ - unsigned char counter; - /* * @state: * * In-memory copy of all FPU registers that we save/restore @@ -340,29 +329,6 @@ struct fpu { * the registers in the FPU are more recent than this state * copy. If the task context-switches away then they get * saved here and represent the FPU state. - * - * After context switches there may be a (short) time period - * during which the in-FPU hardware registers are unchanged - * and still perfectly match this state, if the tasks - * scheduled afterwards are not using the FPU. - * - * This is the 'lazy restore' window of optimization, which - * we track though 'fpu_fpregs_owner_ctx' and 'fpu->last_cpu'. - * - * We detect whether a subsequent task uses the FPU via setting - * CR0::TS to 1, which causes any FPU use to raise a #NM fault. - * - * During this window, if the task gets scheduled again, we - * might be able to skip having to do a restore from this - * memory buffer to the hardware registers - at the cost of - * incurring the overhead of #NM fault traps. - * - * Note that on modern CPUs that support the XSAVEOPT (or other - * optimized XSAVE instructions), we don't use #NM traps anymore, - * as the hardware can track whether FPU registers need saving - * or not. On such CPUs we activate the non-lazy ('eagerfpu') - * logic, which unconditionally saves/restores all FPU state - * across context switches. (if FPU state exists.) */ union fpregs_state state; /* |