On 03/21/2012 04:49 PM, Takuya Yoshikawa wrote:
> From: Takuya Yoshikawa <yoshikawa.takuya@xxxxxxxxxxxxx>
>
> We have PTE_LIST_EXT + 1 pointers in this structure and these 40/20
> bytes do not fit cache lines well. Furthermore, some allocators may
> use 64/32-byte objects for the pte_list_desc cache.
>
> This patch solves this problem by changing PTE_LIST_EXT from 4 to 3.
>
> For shadow paging, the new size is still large enough to hold both the
> kernel and process mappings for usual anonymous pages. For file
> mappings, there may be a slight change in the cache usage.
>
> Note: with EPT/NPT we almost always have a single spte in each reverse
> mapping and we will not see any change by this.
>
> @@ -135,8 +135,6 @@ module_param(dbg, bool, 0644);
> #define PT64_PERM_MASK (PT_PRESENT_MASK | PT_WRITABLE_MASK | PT_USER_MASK \
> | PT64_NX_MASK)
>
> -#define PTE_LIST_EXT 4
> -
> #define ACC_EXEC_MASK 1
> #define ACC_WRITE_MASK PT_WRITABLE_MASK
> #define ACC_USER_MASK PT_USER_MASK
> @@ -151,6 +149,9 @@ module_param(dbg, bool, 0644);
>
> #define SHADOW_PT_INDEX(addr, level) PT64_INDEX(addr, level)
>
> +/* make pte_list_desc fit well in cache line */
> +#define PTE_LIST_EXT 3
> +
> struct pte_list_desc {
> u64 *sptes[PTE_LIST_EXT];
> struct pte_list_desc *more;
We could go even further and have 4 pointers, and use bit 0 to decide
whether it's a next pointer or an sptep.
Not sure it's worth the extra complexity.
--
error compiling committee.c: too many arguments to function
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