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SubjectRe: [RFC] [PATCH] cache pollution aware __copy_from_user_ll()
From
> So I make two APIs. 
> __copy_user_zeroing_nocache()
> __copy_user_zeroing_inatomic_nocache()
>
> The former is a low latency version and the other is a throughput version.

1) using stack to save/restore MMX registers
2) low latency version of cache aware copy
3) __copy_user*_nocache APIs so if you want to use it.

diff -ur linux-2.6.12.4.orig/Makefile linux-2.6.12.4.preempt/Makefile
--- linux-2.6.12.4.orig/Makefile 2005-08-12 14:37:59.000000000 +0900
+++ linux-2.6.12.4.preempt/Makefile 2005-08-18 18:47:07.000000000 +0900
@@ -1,7 +1,7 @@
VERSION = 2
PATCHLEVEL = 6
SUBLEVEL = 12
-EXTRAVERSION = .4.orig
+EXTRAVERSION = .4.preempt
NAME=Woozy Numbat

# *DOCUMENTATION*
diff -ur linux-2.6.12.4.orig/arch/i386/lib/usercopy.c linux-2.6.12.4.preempt/arch/i386/lib/usercopy.c
--- linux-2.6.12.4.orig/arch/i386/lib/usercopy.c 2005-08-05 16:04:37.000000000 +0900
+++ linux-2.6.12.4.preempt/arch/i386/lib/usercopy.c 2005-08-18 19:07:49.000000000 +0900
@@ -10,6 +10,7 @@
#include <linux/highmem.h>
#include <linux/blkdev.h>
#include <linux/module.h>
+#include <asm/i387.h>
#include <asm/uaccess.h>
#include <asm/mmx.h>

@@ -511,6 +512,254 @@
: "memory"); \
} while (0)

+#define MMX_SAVE do { \
+ preempt_disable(); \
+ __asm__ __volatile__ ( \
+ "movl %%cr0,%0 ;\n\t" \
+ "clts ;\n\t" \
+ "movq %%mm0,(%1) ;\n\t" \
+ "movq %%mm1,8(%1) ;\n\t" \
+ "movq %%mm2,16(%1) ;\n\t" \
+ "movq %%mm3,24(%1) ;\n\t" \
+ : "=&r" (cr0) \
+ : "r" (mmx_save) \
+ : "memory"); \
+} while(0)
+
+#define MMX_RESTORE do { \
+ __asm__ __volatile__ ( \
+ "sfence ;\n\t" \
+ "movq (%1),%%mm0 ;\n\t" \
+ "movq 8(%1),%%mm1 ;\n\t" \
+ "movq 16(%1),%%mm2 ;\n\t" \
+ "movq 24(%1),%%mm3 ;\n\t" \
+ "movl %0,%%cr0 ;\n\t" \
+ : \
+ : "r" (cr0), "r" (mmx_save) \
+ : "memory"); \
+ preempt_enable(); \
+} while(0)
+
+#define ALIGN8 __attribute__((aligned(8)))
+
+/* Non Temporal Hint version of mmx_memcpy */
+/* It is cache aware */
+/* hyoshiok@miraclelinux.com */
+static unsigned long
+__copy_user_zeroing_nocache(void *to, const void *from, size_t len)
+{
+ /* Note! gcc doesn't seem to align stack variables properly, so we
+ * need to make use of unaligned loads and stores.
+ */
+ void *p;
+ int i;
+ char mmx_save[8*4] ALIGN8;
+ int cr0;
+
+ if (unlikely(in_interrupt())){
+ __copy_user_zeroing(to, from, len);
+ return len;
+ }
+
+ p = to;
+ i = len >> 6; /* len/64 */
+
+ /* kernel_fpu_begin();*/
+ MMX_SAVE;
+
+ __asm__ __volatile__ (
+ "1: prefetchnta (%0)\n" /* This set is 28 bytes */
+ " prefetchnta 64(%0)\n"
+ " prefetchnta 128(%0)\n"
+ " prefetchnta 192(%0)\n"
+ " prefetchnta 256(%0)\n"
+ "2: \n"
+ ".section .fixup, \"ax\"\n"
+ "3: movw $0x1AEB, 1b\n" /* jmp on 26 bytes */
+ " jmp 2b\n"
+ ".previous\n"
+ ".section __ex_table,\"a\"\n"
+ " .align 4\n"
+ " .long 1b, 3b\n"
+ ".previous"
+ : : "r" (from) );
+
+ for(; i>5; i--)
+ {
+ __asm__ __volatile__ (
+ "1: prefetchnta 320(%0)\n"
+ "2: movq (%0), %%mm0\n"
+ " movq 8(%0), %%mm1\n"
+ " movq 16(%0), %%mm2\n"
+ " movq 24(%0), %%mm3\n"
+ " movntq %%mm0, (%1)\n"
+ " movntq %%mm1, 8(%1)\n"
+ " movntq %%mm2, 16(%1)\n"
+ " movntq %%mm3, 24(%1)\n"
+ " movq 32(%0), %%mm0\n"
+ " movq 40(%0), %%mm1\n"
+ " movq 48(%0), %%mm2\n"
+ " movq 56(%0), %%mm3\n"
+ " movntq %%mm0, 32(%1)\n"
+ " movntq %%mm1, 40(%1)\n"
+ " movntq %%mm2, 48(%1)\n"
+ " movntq %%mm3, 56(%1)\n"
+ ".section .fixup, \"ax\"\n"
+ "3: movw $0x05EB, 1b\n" /* jmp on 5 bytes */
+ " jmp 2b\n"
+ ".previous\n"
+ ".section __ex_table,\"a\"\n"
+ " .align 4\n"
+ " .long 1b, 3b\n"
+ ".previous"
+ : : "r" (from), "r" (to) : "memory");
+ from+=64;
+ to+=64;
+#ifdef CONFIG_PREEMPT
+ if ( (i%64)==0 ) {
+ MMX_RESTORE;
+ MMX_SAVE;
+ };
+#endif
+ }
+
+ for(; i>0; i--)
+ {
+ __asm__ __volatile__ (
+ " movq (%0), %%mm0\n"
+ " movq 8(%0), %%mm1\n"
+ " movq 16(%0), %%mm2\n"
+ " movq 24(%0), %%mm3\n"
+ " movntq %%mm0, (%1)\n"
+ " movntq %%mm1, 8(%1)\n"
+ " movntq %%mm2, 16(%1)\n"
+ " movntq %%mm3, 24(%1)\n"
+ " movq 32(%0), %%mm0\n"
+ " movq 40(%0), %%mm1\n"
+ " movq 48(%0), %%mm2\n"
+ " movq 56(%0), %%mm3\n"
+ " movntq %%mm0, 32(%1)\n"
+ " movntq %%mm1, 40(%1)\n"
+ " movntq %%mm2, 48(%1)\n"
+ " movntq %%mm3, 56(%1)\n"
+ : : "r" (from), "r" (to) : "memory");
+ from+=64;
+ to+=64;
+ }
+ /*
+ * Now do the tail of the block
+ */
+ /* kernel_fpu_end();*/
+ MMX_RESTORE;
+ if(i=(len&63))
+ __copy_user_zeroing(to, from, i);
+ return i;
+}
+
+static unsigned long
+__copy_user_zeroing_inatomic_nocache(void *to, const void *from, size_t len)
+{
+ /* Note! gcc doesn't seem to align stack variables properly, so we
+ * need to make use of unaligned loads and stores.
+ */
+ void *p;
+ int i;
+ char mmx_save[8*4] ALIGN8;
+ int cr0;
+
+ if (unlikely(in_interrupt())){
+ __copy_user_zeroing(to, from, len);
+ return len;
+ }
+
+ p = to;
+ i = len >> 6; /* len/64 */
+
+ /* kernel_fpu_begin();*/
+ MMX_SAVE;
+
+ __asm__ __volatile__ (
+ "1: prefetchnta (%0)\n" /* This set is 28 bytes */
+ " prefetchnta 64(%0)\n"
+ " prefetchnta 128(%0)\n"
+ " prefetchnta 192(%0)\n"
+ " prefetchnta 256(%0)\n"
+ "2: \n"
+ ".section .fixup, \"ax\"\n"
+ "3: movw $0x1AEB, 1b\n" /* jmp on 26 bytes */
+ " jmp 2b\n"
+ ".previous\n"
+ ".section __ex_table,\"a\"\n"
+ " .align 4\n"
+ " .long 1b, 3b\n"
+ ".previous"
+ : : "r" (from) );
+
+ for(; i>5; i--)
+ {
+ __asm__ __volatile__ (
+ "1: prefetchnta 320(%0)\n"
+ "2: movq (%0), %%mm0\n"
+ " movq 8(%0), %%mm1\n"
+ " movq 16(%0), %%mm2\n"
+ " movq 24(%0), %%mm3\n"
+ " movntq %%mm0, (%1)\n"
+ " movntq %%mm1, 8(%1)\n"
+ " movntq %%mm2, 16(%1)\n"
+ " movntq %%mm3, 24(%1)\n"
+ " movq 32(%0), %%mm0\n"
+ " movq 40(%0), %%mm1\n"
+ " movq 48(%0), %%mm2\n"
+ " movq 56(%0), %%mm3\n"
+ " movntq %%mm0, 32(%1)\n"
+ " movntq %%mm1, 40(%1)\n"
+ " movntq %%mm2, 48(%1)\n"
+ " movntq %%mm3, 56(%1)\n"
+ ".section .fixup, \"ax\"\n"
+ "3: movw $0x05EB, 1b\n" /* jmp on 5 bytes */
+ " jmp 2b\n"
+ ".previous\n"
+ ".section __ex_table,\"a\"\n"
+ " .align 4\n"
+ " .long 1b, 3b\n"
+ ".previous"
+ : : "r" (from), "r" (to) : "memory");
+ from+=64;
+ to+=64;
+ }
+
+ for(; i>0; i--)
+ {
+ __asm__ __volatile__ (
+ " movq (%0), %%mm0\n"
+ " movq 8(%0), %%mm1\n"
+ " movq 16(%0), %%mm2\n"
+ " movq 24(%0), %%mm3\n"
+ " movntq %%mm0, (%1)\n"
+ " movntq %%mm1, 8(%1)\n"
+ " movntq %%mm2, 16(%1)\n"
+ " movntq %%mm3, 24(%1)\n"
+ " movq 32(%0), %%mm0\n"
+ " movq 40(%0), %%mm1\n"
+ " movq 48(%0), %%mm2\n"
+ " movq 56(%0), %%mm3\n"
+ " movntq %%mm0, 32(%1)\n"
+ " movntq %%mm1, 40(%1)\n"
+ " movntq %%mm2, 48(%1)\n"
+ " movntq %%mm3, 56(%1)\n"
+ : : "r" (from), "r" (to) : "memory");
+ from+=64;
+ to+=64;
+ }
+ /*
+ * Now do the tail of the block
+ */
+ /* kernel_fpu_end();*/
+ MMX_RESTORE;
+ if(i=(len&63))
+ __copy_user_zeroing(to, from, i);
+ return i;
+}

unsigned long __copy_to_user_ll(void __user *to, const void *from, unsigned long n)
{
@@ -582,6 +831,36 @@
return n;
}

+unsigned long
+__copy_from_user_ll_nocache(void *to, const void __user *from, unsigned long n)
+{
+ BUG_ON((long)n < 0);
+ if (n < 512) {
+ if (movsl_is_ok(to, from, n))
+ __copy_user_zeroing(to, from, n);
+ else
+ n = __copy_user_zeroing_intel(to, from, n);
+ }
+ else
+ n = __copy_user_zeroing_nocache(to, from, n);
+ return n;
+}
+
+unsigned long
+__copy_from_user_ll_inatomic_nocache(void *to, const void __user *from, unsigned long n)
+{
+ BUG_ON((long)n < 0);
+ if (n < 512) {
+ if (movsl_is_ok(to, from, n))
+ __copy_user_zeroing(to, from, n);
+ else
+ n = __copy_user_zeroing_intel(to, from, n);
+ }
+ else
+ n = __copy_user_zeroing_inatomic_nocache(to, from, n);
+ return n;
+}
+
/**
* copy_to_user: - Copy a block of data into user space.
* @to: Destination address, in user space.
diff -ur linux-2.6.12.4.orig/include/asm-i386/uaccess.h linux-2.6.12.4.preempt/include/asm-i386/uaccess.h
--- linux-2.6.12.4.orig/include/asm-i386/uaccess.h 2005-08-05 16:04:37.000000000 +0900
+++ linux-2.6.12.4.preempt/include/asm-i386/uaccess.h 2005-08-18 19:16:55.000000000 +0900
@@ -413,6 +413,10 @@
const void *from, unsigned long n);
unsigned long __must_check __copy_from_user_ll(void *to,
const void __user *from, unsigned long n);
+unsigned long __must_check __copy_from_user_ll_nocache(void *to,
+ const void __user *from, unsigned long n);
+unsigned long __must_check __copy_from_user_ll_inatomic_nocache(void *to,
+ const void __user *from, unsigned long n);

/*
* Here we special-case 1, 2 and 4-byte copy_*_user invocations. On a fault
@@ -502,11 +506,55 @@
}

static inline unsigned long
+__copy_from_user_inatomic_nocache(void *to, const void __user *from, unsigned long n)
+{
+ if (__builtin_constant_p(n)) {
+ unsigned long ret;
+
+ switch (n) {
+ case 1:
+ __get_user_size(*(u8 *)to, from, 1, ret, 1);
+ return ret;
+ case 2:
+ __get_user_size(*(u16 *)to, from, 2, ret, 2);
+ return ret;
+ case 4:
+ __get_user_size(*(u32 *)to, from, 4, ret, 4);
+ return ret;
+ }
+ }
+ return __copy_from_user_ll_inatomic_nocache(to, from, n);
+}
+
+static inline unsigned long
__copy_from_user(void *to, const void __user *from, unsigned long n)
{
might_sleep();
return __copy_from_user_inatomic(to, from, n);
}
+
+static inline unsigned long
+__copy_from_user_nocache(void *to, const void __user *from, unsigned long n)
+{
+ might_sleep();
+ if (__builtin_constant_p(n)) {
+ unsigned long ret;
+
+ switch (n) {
+ case 1:
+ __get_user_size(*(u8 *)to, from, 1, ret, 1);
+ return ret;
+ case 2:
+ __get_user_size(*(u16 *)to, from, 2, ret, 2);
+ return ret;
+ case 4:
+ __get_user_size(*(u32 *)to, from, 4, ret, 4);
+ return ret;
+ }
+ }
+ return __copy_from_user_ll_nocache(to, from, n);
+}
+
unsigned long __must_check copy_to_user(void __user *to,
const void *from, unsigned long n);
unsigned long __must_check copy_from_user(void *to,
diff -ur linux-2.6.12.4.orig/mm/filemap.c linux-2.6.12.4.preempt/mm/filemap.c
--- linux-2.6.12.4.orig/mm/filemap.c 2005-08-05 16:04:37.000000000 +0900
+++ linux-2.6.12.4.preempt/mm/filemap.c 2005-08-16 10:16:06.000000000 +0900
@@ -1727,13 +1727,13 @@
int left;

kaddr = kmap_atomic(page, KM_USER0);
- left = __copy_from_user_inatomic(kaddr + offset, buf, bytes);
+ left = __copy_from_user_inatomic_nocache(kaddr + offset, buf, bytes);
kunmap_atomic(kaddr, KM_USER0);

if (left != 0) {
/* Do it the slow way */
kaddr = kmap(page);
- left = __copy_from_user(kaddr + offset, buf, bytes);
+ left = __copy_from_user_nocache(kaddr + offset, buf, bytes);
kunmap(page);
}
return bytes - left;
@@ -1750,7 +1750,7 @@
int copy = min(bytes, iov->iov_len - base);

base = 0;
- left = __copy_from_user_inatomic(vaddr, buf, copy);
+ left = __copy_from_user_inatomic_nocache(vaddr, buf, copy);
copied += copy;
bytes -= copy;
vaddr += copy;

Regards,
Hiro
--
Hiro Yoshioka
CTO/Miracle Linux Corporation
-
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