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

Hirokazu Takahashi
2005-08-16T04:22:31Z

Hi,

BTW, what are you going to do with the page-faults which may happen
during __copy_user_zeroing_nocache()? The current process may be blocked
in the handler for a while and get FPU registers polluted.
kernel_fpu_begin() won't help the case. This is another issue, though.

> > Thanks.
> >
> > filemap_copy_from_user() calls __copy_from_user_inatomic() calls
> > __copy_from_user_ll().
> >
> > I'll look at the code.
>
> The following is a quick hack of cache aware implementation
> of __copy_from_user_ll() and __copy_from_user_inatomic()
>
> __copy_from_user_ll_nocache() and __copy_from_user_inatomic_nocache()
>
> filemap_copy_from_user() calles __copy_from_user_inatomic_nocache()
> instead of __copy_from_user_inatomic() and reduced cashe miss.
>
> The first column is the cache reference (memory access) and the
> third column is the 3rd level cache miss.
>
> The following example shows the L3 cache miss is reduced from 37410 to 107.
>
> 2.6.12.4 nocache version
> Counted BSQ_CACHE_REFERENCE events (cache references seen by the bus unit) with a unit mask of 0x3f (multiple flags) count 3000
> 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 % samples % app name symbol name
> 120442 6.4106 107 0.5620 vmlinux __copy_user_zeroing_nocache
> 80049 4.2606 578 3.0357 vmlinux journal_add_journal_head
> 69194 3.6829 154 0.8088 vmlinux journal_dirty_metadata
> 67059 3.5692 78 0.4097 vmlinux __find_get_block
> 64145 3.4141 32 0.1681 vmlinux journal_put_journal_head
> pattern9-0-cpu4-0-08161154/summary.out
>
> The 2.6.12.4 original version is
> Counted BSQ_CACHE_REFERENCE events (cache references seen by the bus unit) with a unit mask of 0x3f (multiple flags) count 3000
> 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 % samples % app name symbol name
> 120646 7.4680 37410 62.3355 vmlinux __copy_from_user_ll
> 79508 4.9215 903 1.5046 vmlinux _spin_lock
> 65526 4.0561 873 1.4547 vmlinux journal_add_journal_head
> 59296 3.6704 129 0.2149 vmlinux __find_get_block
> 58647 3.6302 215 0.3582 vmlinux journal_dirty_metadata
>
> What do you think?
>
> Hiro
>
> diff -ur linux-2.6.12.4.orig/Makefile linux-2.6.12.4.nocache/Makefile
> --- linux-2.6.12.4.orig/Makefile 2005-08-12 14:37:59.000000000 +0900
> +++ linux-2.6.12.4.nocache/Makefile 2005-08-16 10:22:31.000000000 +0900
> @@ -1,7 +1,7 @@
> VERSION = 2
> PATCHLEVEL = 6
> SUBLEVEL = 12
> -EXTRAVERSION = .4.orig
> +EXTRAVERSION = .4.nocache
> NAME=Woozy Numbat
>
> # *DOCUMENTATION*
> diff -ur linux-2.6.12.4.orig/arch/i386/lib/usercopy.c linux-2.6.12.4.nocache/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.nocache/arch/i386/lib/usercopy.c 2005-08-16 10:49:59.000000000 +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 +512,110 @@
> : "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;
> + }
> +
> + 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 +687,21 @@
> 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;
> +}
> +
> /**
> * 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/uaccess.h linux-2.6.12.4.nocache/include/asm/uaccess.h
> --- linux-2.6.12.4.orig/include/asm/uaccess.h 2005-08-05 16:04:37.000000000 +0900
> +++ linux-2.6.12.4.nocache/include/asm/uaccess.h 2005-08-16 10:44:05.000000000 +0900
> @@ -413,6 +413,8 @@
> 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);
>
> /*
> * Here we special-case 1, 2 and 4-byte copy_*_user invocations. On a fault
> @@ -502,11 +504,38 @@
> }
>
> 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_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();
> + return __copy_from_user_inatomic_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/include/asm-i386/uaccess.h linux-2.6.12.4.nocache/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.nocache/include/asm-i386/uaccess.h 2005-08-16 10:44:05.000000000 +0900
> @@ -413,6 +413,8 @@
> 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);
>
> /*
> * Here we special-case 1, 2 and 4-byte copy_*_user invocations. On a fault
> @@ -502,11 +504,38 @@
> }
>
> 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_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();
> + return __copy_from_user_inatomic_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/include/linux/autoconf.h linux-2.6.12.4.nocache/include/linux/autoconf.h
> --- linux-2.6.12.4.orig/include/linux/autoconf.h 2005-08-15 16:53:01.000000000 +0900
> +++ linux-2.6.12.4.nocache/include/linux/autoconf.h 2005-08-16 10:32:33.000000000 +0900
> @@ -1,7 +1,7 @@
> /*
> * Automatically generated C config: don't edit
> - * Linux kernel version: 2.6.12.4.orig
> - * Mon Aug 15 16:53:01 2005
> + * Linux kernel version: 2.6.12.4.nocache
> + * Tue Aug 16 10:32:33 2005
> */
> #define AUTOCONF_INCLUDED
> #define CONFIG_X86 1
> diff -ur linux-2.6.12.4.orig/mm/filemap.c linux-2.6.12.4.nocache/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.nocache/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;
> -
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