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    Subject[patch 2/2] x86,fpu: lazy allocation of FPU area
    Only allocate the FPU area when the application actually uses FPU, i.e., in the
    first lazy FPU trap. This could save memory for non-fpu using apps.

    Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
    Cc: Arjan van de Ven <arjan@linux.intel.com>
    ---

    Index: linux-2.6-x86/arch/x86/kernel/i387.c
    ===================================================================
    --- linux-2.6-x86.orig/arch/x86/kernel/i387.c 2008-02-23 18:27:40.000000000 -0800
    +++ linux-2.6-x86/arch/x86/kernel/i387.c 2008-02-23 18:27:41.000000000 -0800
    @@ -9,7 +9,6 @@
    #include <linux/sched.h>
    #include <linux/module.h>
    #include <linux/regset.h>
    -#include <linux/bootmem.h>
    #include <asm/processor.h>
    #include <asm/i387.h>
    #include <asm/math_emu.h>
    @@ -67,7 +66,6 @@
    else
    math_cntxt_size = sizeof(struct i387_fsave_struct);
    #endif
    - init_task.thread.cntxt = alloc_bootmem(math_cntxt_size);
    }

    #ifdef CONFIG_X86_64
    @@ -105,6 +103,9 @@
    return;
    }

    + if (!tsk->thread.cntxt)
    + tsk->thread.cntxt = alloc_cntxt_struct();
    +
    if (cpu_has_fxsr) {
    memset(FXSAVE(tsk), 0, math_cntxt_size);
    FXSAVE(tsk)->cwd = 0x37f;
    Index: linux-2.6-x86/arch/x86/kernel/process.c
    ===================================================================
    --- linux-2.6-x86.orig/arch/x86/kernel/process.c 2008-02-23 18:27:40.000000000 -0800
    +++ linux-2.6-x86/arch/x86/kernel/process.c 2008-02-23 18:27:49.000000000 -0800
    @@ -8,21 +8,25 @@
    static struct kmem_cache *task_struct_cachep;
    static struct kmem_cache *task_cntxt_cachep;

    -struct task_struct * alloc_task_struct(void)
    +union thread_cntxt *alloc_cntxt_struct(void)
    +{
    + return kmem_cache_alloc(task_cntxt_cachep, GFP_KERNEL);
    +}
    +
    +struct task_struct * alloc_task_struct(struct task_struct *src)
    {
    struct task_struct *tsk;
    tsk = kmem_cache_alloc(task_struct_cachep, GFP_KERNEL);
    - if (!tsk)
    - return NULL;
    - tsk->thread.cntxt = kmem_cache_alloc(task_cntxt_cachep, GFP_KERNEL);
    - if (!tsk->thread.cntxt)
    - goto error;
    - WARN_ON((unsigned long)tsk->thread.cntxt & 15);
    + if (tsk && src->thread.cntxt) {
    + tsk->thread.cntxt = alloc_cntxt_struct();
    + if (!tsk->thread.cntxt) {
    + kmem_cache_free(task_struct_cachep, tsk);
    + return NULL;
    + }
    + WARN_ON((unsigned long)tsk->thread.cntxt & 15);
    + } else if (tsk)
    + tsk->thread.cntxt = NULL;
    return tsk;
    -
    -error:
    - kmem_cache_free(task_struct_cachep, tsk);
    - return NULL;
    }

    void memcpy_task_struct(struct task_struct *dst, struct task_struct *src)
    @@ -31,13 +35,21 @@
    ptr = dst->thread.cntxt;
    *dst = *src;
    dst->thread.cntxt = ptr;
    - memcpy(dst->thread.cntxt, src->thread.cntxt, math_cntxt_size);
    + if (src->thread.cntxt)
    + memcpy(dst->thread.cntxt, src->thread.cntxt, math_cntxt_size);
    +}
    +
    +void free_cntxt_struct(struct task_struct *tsk)
    +{
    + if (tsk->thread.cntxt) {
    + kmem_cache_free(task_cntxt_cachep, tsk->thread.cntxt);
    + tsk->thread.cntxt = NULL;
    + }
    }

    void free_task_struct(struct task_struct *tsk)
    {
    - kmem_cache_free(task_cntxt_cachep, tsk->thread.cntxt);
    - tsk->thread.cntxt=NULL;
    + free_cntxt_struct(tsk);
    kmem_cache_free(task_struct_cachep, tsk);
    }

    Index: linux-2.6-x86/include/asm-x86/i387.h
    ===================================================================
    --- linux-2.6-x86.orig/include/asm-x86/i387.h 2008-02-23 18:27:40.000000000 -0800
    +++ linux-2.6-x86/include/asm-x86/i387.h 2008-02-23 18:27:41.000000000 -0800
    @@ -25,6 +25,7 @@
    extern asmlinkage void math_state_restore(void);
    extern void init_thread_context(void);
    extern unsigned int math_cntxt_size;
    +extern union thread_cntxt *alloc_cntxt_struct(void);

    extern user_regset_active_fn fpregs_active, xfpregs_active;
    extern user_regset_get_fn fpregs_get, xfpregs_get, fpregs_soft_get;
    Index: linux-2.6-x86/include/asm-x86/processor.h
    ===================================================================
    --- linux-2.6-x86.orig/include/asm-x86/processor.h 2008-02-23 18:27:40.000000000 -0800
    +++ linux-2.6-x86/include/asm-x86/processor.h 2008-02-23 18:27:41.000000000 -0800
    @@ -743,6 +743,8 @@
    .io_bitmap = { [0 ... IO_BITMAP_LONGS] = ~0 }, \
    }

    +extern void free_cntxt_struct(struct task_struct *);
    +
    #define start_thread(regs, new_eip, new_esp) do { \
    __asm__("movl %0,%%gs": :"r" (0)); \
    regs->fs = 0; \
    @@ -753,6 +755,7 @@
    regs->cs = __USER_CS; \
    regs->ip = new_eip; \
    regs->sp = new_esp; \
    + free_cntxt_struct(current); \
    } while (0)


    Index: linux-2.6-x86/include/asm-x86/thread_info.h
    ===================================================================
    --- linux-2.6-x86.orig/include/asm-x86/thread_info.h 2008-02-23 18:27:40.000000000 -0800
    +++ linux-2.6-x86/include/asm-x86/thread_info.h 2008-02-23 18:27:41.000000000 -0800
    @@ -6,7 +6,7 @@

    #ifndef __ASSEMBLY__
    #define __HAVE_ARCH_TASK_STRUCT_ALLOCATOR
    -extern struct task_struct * alloc_task_struct(void);
    +extern struct task_struct * alloc_task_struct(struct task_struct *src);
    extern void free_task_struct(struct task_struct *tsk);
    extern void memcpy_task_struct(struct task_struct *dst, struct task_struct *src
    );
    Index: linux-2.6-x86/kernel/fork.c
    ===================================================================
    --- linux-2.6-x86.orig/kernel/fork.c 2008-02-23 18:27:40.000000000 -0800
    +++ linux-2.6-x86/kernel/fork.c 2008-02-23 18:27:41.000000000 -0800
    @@ -85,7 +85,7 @@
    }

    #ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR
    -# define alloc_task_struct() kmem_cache_alloc(task_struct_cachep, GFP_KERNEL)
    +# define alloc_task_struct(src) kmem_cache_alloc(task_struct_cachep, GFP_KERNEL)
    # define free_task_struct(tsk) kmem_cache_free(task_struct_cachep, (tsk))
    # define memcpy_task_struct(dst, src) do { *dst = *src; } while (0)
    static struct kmem_cache *task_struct_cachep;
    @@ -174,7 +174,7 @@

    prepare_to_copy(orig);

    - tsk = alloc_task_struct();
    + tsk = alloc_task_struct(orig);
    if (!tsk)
    return NULL;

    --



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