diff options
Diffstat (limited to 'arch/arm/lib')
| -rw-r--r-- | arch/arm/lib/uaccess_with_memcpy.c | 75 |
1 files changed, 73 insertions, 2 deletions
diff --git a/arch/arm/lib/uaccess_with_memcpy.c b/arch/arm/lib/uaccess_with_memcpy.c index 92838e79654..6b967ffb655 100644 --- a/arch/arm/lib/uaccess_with_memcpy.c +++ b/arch/arm/lib/uaccess_with_memcpy.c @@ -106,7 +106,7 @@ __copy_to_user(void __user *to, const void *from, unsigned long n) * With frame pointer disabled, tail call optimization kicks in * as well making this test almost invisible. */ - if (n < 1024) + if (n < 64) return __copy_to_user_std(to, from, n); return __copy_to_user_memcpy(to, from, n); } @@ -151,7 +151,78 @@ out: unsigned long __clear_user(void __user *addr, unsigned long n) { /* See rational for this in __copy_to_user() above. */ - if (n < 256) + if (n < 64) return __clear_user_std(addr, n); return __clear_user_memset(addr, n); } + +#if 0 + +/* + * This code is disabled by default, but kept around in case the chosen + * thresholds need to be revalidated. Some overhead (small but still) + * would be implied by a runtime determined variable threshold, and + * so far the measurement on concerned targets didn't show a worthwhile + * variation. + * + * Note that a fairly precise sched_clock() implementation is needed + * for results to make some sense. + */ + +#include <linux/vmalloc.h> + +static int __init test_size_treshold(void) +{ + struct page *src_page, *dst_page; + void *user_ptr, *kernel_ptr; + unsigned long long t0, t1, t2; + int size, ret; + + ret = -ENOMEM; + src_page = alloc_page(GFP_KERNEL); + if (!src_page) + goto no_src; + dst_page = alloc_page(GFP_KERNEL); + if (!dst_page) + goto no_dst; + kernel_ptr = page_address(src_page); + user_ptr = vmap(&dst_page, 1, VM_IOREMAP, __pgprot(__P010)); + if (!user_ptr) + goto no_vmap; + + /* warm up the src page dcache */ + ret = __copy_to_user_memcpy(user_ptr, kernel_ptr, PAGE_SIZE); + + for (size = PAGE_SIZE; size >= 4; size /= 2) { + t0 = sched_clock(); + ret |= __copy_to_user_memcpy(user_ptr, kernel_ptr, size); + t1 = sched_clock(); + ret |= __copy_to_user_std(user_ptr, kernel_ptr, size); + t2 = sched_clock(); + printk("copy_to_user: %d %llu %llu\n", size, t1 - t0, t2 - t1); + } + + for (size = PAGE_SIZE; size >= 4; size /= 2) { + t0 = sched_clock(); + ret |= __clear_user_memset(user_ptr, size); + t1 = sched_clock(); + ret |= __clear_user_std(user_ptr, size); + t2 = sched_clock(); + printk("clear_user: %d %llu %llu\n", size, t1 - t0, t2 - t1); + } + + if (ret) + ret = -EFAULT; + + vunmap(user_ptr); +no_vmap: + put_page(dst_page); +no_dst: + put_page(src_page); +no_src: + return ret; +} + +subsys_initcall(test_size_treshold); + +#endif |