Messages in this thread Patch in this message | | | Date | Sun, 14 Sep 2003 13:17:10 +0200 | From | Manfred Spraul <> | Subject | [PATCH] add likely around access_ok for uaccess |
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Hi,
while trying to figure out why sysv msg is around 30% slower than pipes for data transfers I noticed that gcc's autodetection (3.2.2) guesses the "if(access_ok())" tests in uaccess.h wrong and puts the error memset into the direct path and the copy out of line.
The attached patch adds likely to the tests - any objections? What about the archs except i386?
-- Manfred --- 2.6/include/asm-i386/uaccess.h 2003-09-12 21:53:58.000000000 +0200 +++ build-2.6/include/asm-i386/uaccess.h 2003-09-14 12:56:19.000000000 +0200 @@ -300,7 +300,7 @@ long __pu_err = -EFAULT; \ __typeof__(*(ptr)) *__pu_addr = (ptr); \ might_sleep(); \ - if (access_ok(VERIFY_WRITE,__pu_addr,size)) \ + if (likely(access_ok(VERIFY_WRITE,__pu_addr,size))) \ __put_user_size((x),__pu_addr,(size),__pu_err,-EFAULT); \ __pu_err; \ }) @@ -510,7 +510,7 @@ direct_copy_to_user(void __user *to, const void *from, unsigned long n) { might_sleep(); - if (access_ok(VERIFY_WRITE, to, n)) + if (likely(access_ok(VERIFY_WRITE, to, n))) n = __direct_copy_to_user(to, from, n); return n; } @@ -535,7 +535,7 @@ direct_copy_from_user(void *to, const void __user *from, unsigned long n) { might_sleep(); - if (access_ok(VERIFY_READ, from, n)) + if (likely(access_ok(VERIFY_READ, from, n))) n = __direct_copy_from_user(to, from, n); else memset(to, 0, n); | |