Re: [RFC] [PATCH] cache pollution aware __copy_from_user_ll()

Hiro Yoshioka
2005-08-22T23:17:29Z

Hi,

It seems to me this mail does not go out.
So resending it.

> On 8/18/05, Hiro Yoshioka <hyoshiok@miraclelinux.com> wrote:
> > 1) using stack to save/restore MMX registers
>
> It seems to me that it has some regression.
> I'd like to rollback it and use kernel_fpu_begin() and kernel_fpu_end().

The following is a current version of cache aware copy_from_user_ll.

1) using kernel_fpu_begin()/kernel_fpu_end()
2) low latency version of cache aware copy
3) __copy_user*_nocache APIs so if you want to use it.
(There is no change in the current APIs.)

Some performance data are

Total of GLOBAL_POWER_EVENTS (CPU cycle samples)

2.6.12.4.orig 1921587
2.6.12.4.preempt 1634411
163411/1921587=85.06% (15% reduction)

BSQ_CACHE_REFERENCE (L3 cache miss)
2.6.12.4.orig 57427
2.6.12.4.preempt 17398

samples %
37408 65.1412 vmlinux __copy_from_user_ll
51 0.2931 vmlinux __copy_user_zeroing_inatomic_nocache
51/37408=0.136% (99.86% reduction)

Top 5 2.6.12.4.orig
Counted GLOBAL_POWER_EVENTS events (time during which processor is not stopped) with a unit mask of 0x01 (mandatory) count 100000
samples % app name symbol name
287643 14.9692 vmlinux __copy_from_user_ll
72660 3.7813 vmlinux journal_add_journal_head
65011 3.3832 vmlinux do_get_write_access
50618 2.6342 vmlinux journal_put_journal_head
48068 2.5015 vmlinux journal_dirty_metadata
pattern9-0-cpu4-0-08191743/summary.out

Counted BSQ_CACHE_REFERENCE events (cache references seen by the bus unit) with a unit mask of 0x3f (multiple flags) count 3000
samples % app name symbol name
134756 7.9364 vmlinux __copy_from_user_ll
57735 3.4003 vmlinux journal_add_journal_head
50653 2.9832 vmlinux __find_get_block
44522 2.6221 vmlinux journal_put_journal_head
38928 2.2927 vmlinux journal_dirty_metadata
pattern9-0-cpu4-0-08191741/summary.out

Counted BSQ_CACHE_REFERENCE events (cache references seen by the bus unit) with a unit mask of 0x200 (read 3rd level cache miss) count 3000
samples % app name symbol name
37408 65.1412 vmlinux __copy_from_user_ll
953 1.6595 vmlinux blk_rq_map_sg
886 1.5429 vmlinux sub_preempt_count
680 1.1841 vmlinux journal_add_journal_head
598 1.0413 vmlinux journal_commit_transaction
pattern9-0-cpu4-0-08191720/summary.out

Top 5 2.6.12.4.preempt
Counted GLOBAL_POWER_EVENTS events (time during which processor is not stopped) with a unit mask of 0x01 (mandatory) count 100000
samples % app name symbol name
123531 7.5582 vmlinux __copy_user_zeroing_inatomic_nocache
64820 3.9660 vmlinux journal_add_journal_head
60460 3.6992 vmlinux do_get_write_access
47172 2.8862 vmlinux journal_put_journal_head
46753 2.8606 vmlinux journal_dirty_metadata
pattern9-0-cpu4-0-08190838/summary.out

Counted BSQ_CACHE_REFERENCE events (cache references seen by the bus unit) with a unit mask of 0x3f (multiple flags) count 3000
samples % app name symbol name
126762 6.7993 vmlinux __copy_user_zeroing_inatomic_nocache
79803 4.2805 vmlinux journal_add_journal_head
70271 3.7692 vmlinux journal_dirty_metadata
66146 3.5480 vmlinux __find_get_block
58082 3.1154 vmlinux journal_put_journal_head
pattern9-0-cpu4-0-08190855/summary.out

Counted BSQ_CACHE_REFERENCE events (cache references seen by the bus unit) with a unit mask of 0x200 (read 3rd level cache miss) count 3000
samples % app name symbol name
901 5.1788 vmlinux blk_rq_map_sg
675 3.8798 vmlinux journal_commit_transaction
637 3.6613 vmlinux radix_tree_delete
605 3.4774 vmlinux journal_add_journal_head
580 3.3337 vmlinux release_pages
...
51 0.2931 vmlinux __copy_user_zeroing_inatomic_nocache
...
1 0.0057 vmlinux __copy_from_user_ll_inatomic_nocache
pattern9-0-cpu4-0-08190859/summary.out

2.6.12.4-usercopy.c.patch.050819
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 2005-08-19 08:25:08.000000000 +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 +512,216 @@
: "memory"); \
} while (0)

+/* 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;
+
+ if (unlikely(in_interrupt())){
+ __copy_user_zeroing(to, from, len);
+ return len;
+ }
+
+ p = to;
+ i = len >> 6; /* len/64 */
+
+ kernel_fpu_begin();
+
+ __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%256)==0 ) {
+ kernel_fpu_end();
+ kernel_fpu_begin();
+ };
+#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();
+ 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;
+
+ if (unlikely(in_interrupt())){
+ __copy_user_zeroing(to, from, len);
+ return len;
+ }
+
+ p = to;
+ i = len >> 6; /* len/64 */
+
+ kernel_fpu_begin();
+
+ __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();
+ 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 +793,36 @@
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;

--
Hiro Yoshioka
mailto:hyoshiok at miraclelinux.com