On 06/09/2010 10:20 AM, Dave McCracken wrote:
> Two new hypercalls were recently added to the Xen hypervisor to mark
> and unmark hugepages as in use. Once a hugepage has been marked,
> actually mapping the hugepage is sped up by a significant amount (more
> than 20 times faster).
>
> This patch marks hugepages when they are added to the hugepage pool
> and unmarks them when they are removed. It also checks to make sure
> each hugepage is contiguous at the machine level.
>
> Signed-off-by: Dave McCracken <dave.mccracken@xxxxxxxxxx>
>
> --------
>
>
> --- next/arch/x86/xen/mmu.c 2010-06-01 11:41:54.000000000 -0500
> +++ next-fh//arch/x86/xen/mmu.c 2010-06-02 08:45:01.000000000 -0500
> @@ -2531,3 +2531,51 @@ static int __init xen_mmu_debugfs(void)
> fs_initcall(xen_mmu_debugfs);
>
> #endif /* CONFIG_XEN_DEBUG_FS */
> +
> +static int mark_ok = 1;
>
__read_mostly
> +
> +int arch_prepare_hugepage(struct page *page)
> +{
> + struct mmuext_op op;
> + unsigned long pfn, mfn, m;
> + int i;
> + int rc;
> +
> + pfn = page_to_pfn(page);
> + mfn = pfn_to_mfn(pfn);
> + if (mfn & ((HPAGE_SIZE/PAGE_SIZE)-1)) {
> + printk("Guest pages are not properly aligned to use
> hugepages\n");
>
Don't use printk to do this. Use WARN() to print a stack trace so you
can work out who's doing this.
> + return 1;
> + }
> + for (i = 0, m = mfn; i < HPAGE_SIZE/PAGE_SIZE; i++, pfn++, m++) {
> + if (pfn_to_mfn(pfn) != m) {
> + printk("Guest pages are not properly aligned to use
> hugepages\n");
>
Isn't this a superset of the previous test?
> + return 1;
> + }
> + }
> + /* It's ok if this fails. We just fall back to the slow refcounting */
> + if (mark_ok) {
> + op.cmd = MMUEXT_MARK_SUPER;
> + op.arg1.mfn = mfn;
> + rc = HYPERVISOR_mmuext_op(&op, 1, NULL, DOMID_SELF);
> + if (rc) {
> + if (rc == -ENOSYS) {
> + mark_ok = 0;
> + return 0;
> + }
> + return 1;
> + }
> + }
> + return 0;
> +}
> +
> +void arch_release_hugepage(struct page *page)
> +{
> + struct mmuext_op op;
> +
> + if (mark_ok) {
> + op.cmd = MMUEXT_UNMARK_SUPER;
> + op.arg1.mfn = pfn_to_mfn(page_to_pfn(page));
> + HYPERVISOR_mmuext_op(&op, 1, NULL, DOMID_SELF);
> + }
> +}
> --- next/arch/x86/include/asm/hugetlb.h 2010-06-01 11:41:54.000000000
> -0500
> +++ next-fh//arch/x86/include/asm/hugetlb.h 2010-06-02 08:37:58.000000000
> -0500
> @@ -95,6 +95,10 @@ static inline int huge_ptep_set_access_f
> return changed;
> }
>
> +#ifdef CONFIG_XEN
> +int arch_prepare_hugepage(struct page *page);
> +void arch_release_hugepage(struct page *page);
> +#else
> static inline int arch_prepare_hugepage(struct page *page)
> {
> return 0;
> @@ -103,5 +107,6 @@ static inline int arch_prepare_hugepage(
> static inline void arch_release_hugepage(struct page *page)
> {
> }
> +#endif
>
That won't work. What if you boot a CONFIG_XEN kernel native?
Something like:
#ifdef CONFIG_XEN
int xen_prepare_hugepage(struct page *page);
#else
static inline int xen_prepare_hugepage(struct page *page)
{
return 0;
}
#endif
static inline int arch_prepare_hugepage(struct page *page)
{
if (xen_pv_domain())
return xen_prepare_hugepage(page);
return 0;
}
might work better.
J
>
> #endif /* _ASM_X86_HUGETLB_H */
> --- next/include/xen/interface/xen.h 2010-06-01 11:41:59.000000000 -0500
> +++ next-fh//include/xen/interface/xen.h 2010-06-02 08:38:50.000000000
> -0500
> @@ -167,6 +167,19 @@
> * cmd: MMUEXT_SET_LDT
> * linear_addr: Linear address of LDT base (NB. must be page-aligned).
> * nr_ents: Number of entries in LDT.
> + *
> + * cmd: MMUEXT_CLEAR_PAGE
> + * mfn: Machine frame number to be cleared.
> + *
> + * cmd: MMUEXT_COPY_PAGE
> + * mfn: Machine frame number of the destination page.
> + * src_mfn: Machine frame number of the source page.
> + *
> + * cmd: MMUEXT_MARK_SUPER
> + * mfn: Machine frame number of head of superpage to be marked.
> + *
> + * cmd: MMUEXT_UNMARK_SUPER
> + * mfn: Machine frame number of head of superpage to be cleared.
> */
> #define MMUEXT_PIN_L1_TABLE 0
> #define MMUEXT_PIN_L2_TABLE 1
> @@ -183,6 +196,10 @@
> #define MMUEXT_FLUSH_CACHE 12
> #define MMUEXT_SET_LDT 13
> #define MMUEXT_NEW_USER_BASEPTR 15
> +#define MMUEXT_CLEAR_PAGE 16
> +#define MMUEXT_COPY_PAGE 17
> +#define MMUEXT_MARK_SUPER 19
> +#define MMUEXT_UNMARK_SUPER 20
>
> #ifndef __ASSEMBLY__
> #include <linux/types.h>
>
>
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