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SubjectRe: [PATCH] perf, x86: Optimize intel_pmu_pebs_fixup_ip()
On Thu, Oct 17, 2013 at 11:41:45AM +0200, Peter Zijlstra wrote:
> On Thu, Oct 17, 2013 at 01:07:12AM +0200, Peter Zijlstra wrote:
> > On Wed, Oct 16, 2013 at 11:03:19PM +0200, Peter Zijlstra wrote:
> > > Anyway; if you want to have a go at this, feel free.
> >
> > OK, couldn't help myself; completely untested patch below.
> >
> > I think the full once copy it best for the decode as even with the below
> > interface you'd end up doing a lot of duplicate copying due to the
> > variable size insn mess.
>
> Duh, a very small tweak would make it work for that and avoid most of
> the memcpy()s.

Hmm, for some reason, even though copy_from_user_nmi_iter is super fast
now, the while(to < ip) count increased dramatically and so did my
latency. :-(

Not sure what happened between your pretty patch yesterday and this
direction.

Cheers,
Don

>
> ---
> arch/x86/include/asm/uaccess.h | 13 +++++
> arch/x86/kernel/cpu/perf_event.c | 32 +++++------
> arch/x86/kernel/cpu/perf_event_intel_ds.c | 21 ++++---
> arch/x86/lib/usercopy.c | 91 ++++++++++++++++++++++++++++++-
> arch/x86/mm/gup.c | 63 +++++++++++++--------
> 5 files changed, 165 insertions(+), 55 deletions(-)
>
> diff --git a/arch/x86/include/asm/uaccess.h b/arch/x86/include/asm/uaccess.h
> index 5838fa911aa0..a341de0eadd1 100644
> --- a/arch/x86/include/asm/uaccess.h
> +++ b/arch/x86/include/asm/uaccess.h
> @@ -516,6 +516,19 @@ struct __large_struct { unsigned long buf[100]; };
>
> extern unsigned long
> copy_from_user_nmi(void *to, const void __user *from, unsigned long n);
> +
> +struct copy_from_user_nmi_state {
> + void *map;
> + unsigned long address;
> + unsigned long flags;
> +};
> +
> +extern void *
> +copy_from_user_nmi_iter(void *to, const void __user *from,
> + unsigned long n, struct copy_from_user_nmi_state *state);
> +extern void
> +copy_from_user_nmi_end(struct copy_from_user_nmi_state *state);
> +
> extern __must_check long
> strncpy_from_user(char *dst, const char __user *src, long count);
>
> diff --git a/arch/x86/kernel/cpu/perf_event.c b/arch/x86/kernel/cpu/perf_event.c
> index 19c9d86d2f04..c917fe470861 100644
> --- a/arch/x86/kernel/cpu/perf_event.c
> +++ b/arch/x86/kernel/cpu/perf_event.c
> @@ -1979,8 +1979,9 @@ static inline int
> perf_callchain_user32(struct pt_regs *regs, struct perf_callchain_entry *entry)
> {
> /* 32-bit process in 64-bit kernel. */
> + struct copy_from_user_nmi_state state = { NULL };
> unsigned long ss_base, cs_base;
> - struct stack_frame_ia32 frame;
> + struct stack_frame_ia32 frame, *f;
> const void __user *fp;
>
> if (!test_thread_flag(TIF_IA32))
> @@ -1991,20 +1992,17 @@ perf_callchain_user32(struct pt_regs *regs, struct perf_callchain_entry *entry)
>
> fp = compat_ptr(ss_base + regs->bp);
> while (entry->nr < PERF_MAX_STACK_DEPTH) {
> - unsigned long bytes;
> - frame.next_frame = 0;
> - frame.return_address = 0;
> -
> - bytes = copy_from_user_nmi(&frame, fp, sizeof(frame));
> - if (bytes != sizeof(frame))
> + f = copy_from_user_nmi_iter(&frame, fp, sizeof(frame), &state);
> + if (!f)
> break;
>
> if (!valid_user_frame(fp, sizeof(frame)))
> break;
>
> - perf_callchain_store(entry, cs_base + frame.return_address);
> - fp = compat_ptr(ss_base + frame.next_frame);
> + perf_callchain_store(entry, cs_base + f->return_address);
> + fp = compat_ptr(ss_base + f->next_frame);
> }
> + copy_from_user_nmi_end(&state);
> return 1;
> }
> #else
> @@ -2018,7 +2016,8 @@ perf_callchain_user32(struct pt_regs *regs, struct perf_callchain_entry *entry)
> void
> perf_callchain_user(struct perf_callchain_entry *entry, struct pt_regs *regs)
> {
> - struct stack_frame frame;
> + struct copy_from_user_nmi_state state = { NULL };
> + struct stack_frame frame, *f;
> const void __user *fp;
>
> if (perf_guest_cbs && perf_guest_cbs->is_in_guest()) {
> @@ -2043,20 +2042,17 @@ perf_callchain_user(struct perf_callchain_entry *entry, struct pt_regs *regs)
> return;
>
> while (entry->nr < PERF_MAX_STACK_DEPTH) {
> - unsigned long bytes;
> - frame.next_frame = NULL;
> - frame.return_address = 0;
> -
> - bytes = copy_from_user_nmi(&frame, fp, sizeof(frame));
> - if (bytes != sizeof(frame))
> + f = copy_from_user_nmi_iter(&frame, fp, sizeof(frame), &state);
> + if (!f)
> break;
>
> if (!valid_user_frame(fp, sizeof(frame)))
> break;
>
> - perf_callchain_store(entry, frame.return_address);
> - fp = frame.next_frame;
> + perf_callchain_store(entry, f->return_address);
> + fp = f->next_frame;
> }
> + copy_from_user_nmi_end(&state);
> }
>
> /*
> diff --git a/arch/x86/kernel/cpu/perf_event_intel_ds.c b/arch/x86/kernel/cpu/perf_event_intel_ds.c
> index 32e9ed81cd00..5bd3f2091da9 100644
> --- a/arch/x86/kernel/cpu/perf_event_intel_ds.c
> +++ b/arch/x86/kernel/cpu/perf_event_intel_ds.c
> @@ -725,10 +725,14 @@ void intel_pmu_pebs_disable_all(void)
> static int intel_pmu_pebs_fixup_ip(struct pt_regs *regs)
> {
> struct cpu_hw_events *cpuc = &__get_cpu_var(cpu_hw_events);
> + struct copy_from_user_nmi_state state = { NULL };
> unsigned long from = cpuc->lbr_entries[0].from;
> unsigned long old_to, to = cpuc->lbr_entries[0].to;
> unsigned long ip = regs->ip;
> + u8 buf[MAX_INSN_SIZE];
> + struct insn insn;
> int is_64bit = 0;
> + void *kaddr;
>
> /*
> * We don't need to fixup if the PEBS assist is fault like
> @@ -764,19 +768,12 @@ static int intel_pmu_pebs_fixup_ip(struct pt_regs *regs)
> }
>
> do {
> - struct insn insn;
> - u8 buf[MAX_INSN_SIZE];
> - void *kaddr;
> -
> old_to = to;
> if (!kernel_ip(ip)) {
> - int bytes, size = MAX_INSN_SIZE;
> -
> - bytes = copy_from_user_nmi(buf, (void __user *)to, size);
> - if (bytes != size)
> - return 0;
> -
> - kaddr = buf;
> + kaddr = copy_from_user_nmi_iter(buf, (void __user *)to,
> + MAX_INSN_SIZE, &state);
> + if (!kaddr)
> + break;
> } else
> kaddr = (void *)to;
>
> @@ -788,6 +785,8 @@ static int intel_pmu_pebs_fixup_ip(struct pt_regs *regs)
> to += insn.length;
> } while (to < ip);
>
> + copy_from_user_nmi_end(&state);
> +
> if (to == ip) {
> set_linear_ip(regs, old_to);
> return 1;
> diff --git a/arch/x86/lib/usercopy.c b/arch/x86/lib/usercopy.c
> index 4f74d94c8d97..da6c36a8b842 100644
> --- a/arch/x86/lib/usercopy.c
> +++ b/arch/x86/lib/usercopy.c
> @@ -10,6 +10,8 @@
> #include <asm/word-at-a-time.h>
> #include <linux/sched.h>
>
> +extern int ___get_user_pages_fast(unsigned long start, int nr_pages, int flags,
> + struct page **pages);
> /*
> * best effort, GUP based copy_from_user() that is NMI-safe
> */
> @@ -18,6 +20,7 @@ copy_from_user_nmi(void *to, const void __user *from, unsigned long n)
> {
> unsigned long offset, addr = (unsigned long)from;
> unsigned long size, len = 0;
> + unsigned long flags;
> struct page *page;
> void *map;
> int ret;
> @@ -26,9 +29,12 @@ copy_from_user_nmi(void *to, const void __user *from, unsigned long n)
> return len;
>
> do {
> - ret = __get_user_pages_fast(addr, 1, 0, &page);
> - if (!ret)
> + local_irq_save(flags);
> + ret = ___get_user_pages_fast(addr, 1, 0, &page);
> + if (!ret) {
> + local_irq_restore(flags);
> break;
> + }
>
> offset = addr & (PAGE_SIZE - 1);
> size = min(PAGE_SIZE - offset, n - len);
> @@ -36,7 +42,7 @@ copy_from_user_nmi(void *to, const void __user *from, unsigned long n)
> map = kmap_atomic(page);
> memcpy(to, map+offset, size);
> kunmap_atomic(map);
> - put_page(page);
> + local_irq_restore(flags);
>
> len += size;
> to += size;
> @@ -47,3 +53,82 @@ copy_from_user_nmi(void *to, const void __user *from, unsigned long n)
> return len;
> }
> EXPORT_SYMBOL_GPL(copy_from_user_nmi);
> +
> +void *copy_from_user_nmi_iter(void *to, const void __user *from,
> + unsigned long n, struct copy_from_user_nmi_state *state)
> +{
> + unsigned long offset, addr = (unsigned long)from;
> + unsigned long size, len = 0;
> + unsigned long flags;
> + struct page *page;
> + void *map, *_to = to;
> + int ret;
> +
> + if (__range_not_ok(from, n, TASK_SIZE))
> + return NULL;
> +
> + if (state->map) {
> + if ((state->address >> PAGE_SHIFT) ==
> + (addr >> PAGE_SHIFT)) {
> + flags = state->flags;
> + map = state->map;
> + goto got_page;
> + }
> + kunmap_atomic(state->map);
> + local_irq_restore(state->flags);
> + }
> +
> + for (;;) {
> + local_irq_save(flags);
> + ret = ___get_user_pages_fast(addr, 1, 0, &page);
> + if (!ret) {
> + local_irq_restore(flags);
> + state->map = NULL;
> + return NULL;
> + }
> +
> + map = kmap_atomic(page);
> +
> +got_page:
> + offset = addr & (PAGE_SIZE - 1);
> + size = min(PAGE_SIZE - offset, n - len);
> +
> + /*
> + * If the entire desired range falls within the one page
> + * avoid the copy and return a pointer into the kmap.
> + */
> + if (size == n) {
> + _to = map + offset;
> + break;
> + }
> +
> + memcpy(to, map+offset, size);
> + len += size;
> +
> + if (len == n)
> + break;
> +
> + to += size;
> + addr += size;
> +
> + kunmap_atomic(map);
> + local_irq_restore(flags);
> + }
> +
> + state->address = addr;
> + state->flags = flags;
> + state->map = map;
> +
> + return _to;
> +}
> +EXPORT_SYMBOL_GPL(copy_from_user_nmi_iter);
> +
> +void copy_from_user_nmi_end(struct copy_from_user_nmi_state *state)
> +{
> + if (state->map) {
> + kunmap_atomic(state->map);
> + local_irq_restore(state->flags);
> + state->map = NULL;
> + }
> +}
> +EXPORT_SYMBOL_GPL(copy_from_user_nmi_end);
> diff --git a/arch/x86/mm/gup.c b/arch/x86/mm/gup.c
> index dd74e46828c0..e383caf323e4 100644
> --- a/arch/x86/mm/gup.c
> +++ b/arch/x86/mm/gup.c
> @@ -63,19 +63,22 @@ static inline pte_t gup_get_pte(pte_t *ptep)
> #endif
> }
>
> +#define GUPF_GET 0x01
> +#define GUPF_WRITE 0x02
> +
> /*
> * The performance critical leaf functions are made noinline otherwise gcc
> * inlines everything into a single function which results in too much
> * register pressure.
> */
> static noinline int gup_pte_range(pmd_t pmd, unsigned long addr,
> - unsigned long end, int write, struct page **pages, int *nr)
> + unsigned long end, int flags, struct page **pages, int *nr)
> {
> unsigned long mask;
> pte_t *ptep;
>
> mask = _PAGE_PRESENT|_PAGE_USER;
> - if (write)
> + if (flags & GUPF_WRITE)
> mask |= _PAGE_RW;
>
> ptep = pte_offset_map(&pmd, addr);
> @@ -89,7 +92,8 @@ static noinline int gup_pte_range(pmd_t pmd, unsigned long addr,
> }
> VM_BUG_ON(!pfn_valid(pte_pfn(pte)));
> page = pte_page(pte);
> - get_page(page);
> + if (flags & GUPF_GET)
> + get_page(page);
> SetPageReferenced(page);
> pages[*nr] = page;
> (*nr)++;
> @@ -109,7 +113,7 @@ static inline void get_head_page_multiple(struct page *page, int nr)
> }
>
> static noinline int gup_huge_pmd(pmd_t pmd, unsigned long addr,
> - unsigned long end, int write, struct page **pages, int *nr)
> + unsigned long end, int flags, struct page **pages, int *nr)
> {
> unsigned long mask;
> pte_t pte = *(pte_t *)&pmd;
> @@ -117,7 +121,7 @@ static noinline int gup_huge_pmd(pmd_t pmd, unsigned long addr,
> int refs;
>
> mask = _PAGE_PRESENT|_PAGE_USER;
> - if (write)
> + if (flags & GUPF_WRITE)
> mask |= _PAGE_RW;
> if ((pte_flags(pte) & mask) != mask)
> return 0;
> @@ -131,19 +135,20 @@ static noinline int gup_huge_pmd(pmd_t pmd, unsigned long addr,
> do {
> VM_BUG_ON(compound_head(page) != head);
> pages[*nr] = page;
> - if (PageTail(page))
> + if ((flags & GUPF_GET) && PageTail(page))
> get_huge_page_tail(page);
> (*nr)++;
> page++;
> refs++;
> } while (addr += PAGE_SIZE, addr != end);
> - get_head_page_multiple(head, refs);
> + if (flags & GUPF_GET)
> + get_head_page_multiple(head, refs);
>
> return 1;
> }
>
> static int gup_pmd_range(pud_t pud, unsigned long addr, unsigned long end,
> - int write, struct page **pages, int *nr)
> + int flags, struct page **pages, int *nr)
> {
> unsigned long next;
> pmd_t *pmdp;
> @@ -167,10 +172,10 @@ static int gup_pmd_range(pud_t pud, unsigned long addr, unsigned long end,
> if (pmd_none(pmd) || pmd_trans_splitting(pmd))
> return 0;
> if (unlikely(pmd_large(pmd))) {
> - if (!gup_huge_pmd(pmd, addr, next, write, pages, nr))
> + if (!gup_huge_pmd(pmd, addr, next, flags, pages, nr))
> return 0;
> } else {
> - if (!gup_pte_range(pmd, addr, next, write, pages, nr))
> + if (!gup_pte_range(pmd, addr, next, flags, pages, nr))
> return 0;
> }
> } while (pmdp++, addr = next, addr != end);
> @@ -179,7 +184,7 @@ static int gup_pmd_range(pud_t pud, unsigned long addr, unsigned long end,
> }
>
> static noinline int gup_huge_pud(pud_t pud, unsigned long addr,
> - unsigned long end, int write, struct page **pages, int *nr)
> + unsigned long end, int flags, struct page **pages, int *nr)
> {
> unsigned long mask;
> pte_t pte = *(pte_t *)&pud;
> @@ -187,7 +192,7 @@ static noinline int gup_huge_pud(pud_t pud, unsigned long addr,
> int refs;
>
> mask = _PAGE_PRESENT|_PAGE_USER;
> - if (write)
> + if (flags & GUPF_WRITE)
> mask |= _PAGE_RW;
> if ((pte_flags(pte) & mask) != mask)
> return 0;
> @@ -201,19 +206,20 @@ static noinline int gup_huge_pud(pud_t pud, unsigned long addr,
> do {
> VM_BUG_ON(compound_head(page) != head);
> pages[*nr] = page;
> - if (PageTail(page))
> + if ((flags & GUPF_GET) && PageTail(page))
> get_huge_page_tail(page);
> (*nr)++;
> page++;
> refs++;
> } while (addr += PAGE_SIZE, addr != end);
> - get_head_page_multiple(head, refs);
> + if (flags & GUPF_GET)
> + get_head_page_multiple(head, refs);
>
> return 1;
> }
>
> static int gup_pud_range(pgd_t pgd, unsigned long addr, unsigned long end,
> - int write, struct page **pages, int *nr)
> + int flags, struct page **pages, int *nr)
> {
> unsigned long next;
> pud_t *pudp;
> @@ -226,10 +232,10 @@ static int gup_pud_range(pgd_t pgd, unsigned long addr, unsigned long end,
> if (pud_none(pud))
> return 0;
> if (unlikely(pud_large(pud))) {
> - if (!gup_huge_pud(pud, addr, next, write, pages, nr))
> + if (!gup_huge_pud(pud, addr, next, flags, pages, nr))
> return 0;
> } else {
> - if (!gup_pmd_range(pud, addr, next, write, pages, nr))
> + if (!gup_pmd_range(pud, addr, next, flags, pages, nr))
> return 0;
> }
> } while (pudp++, addr = next, addr != end);
> @@ -241,13 +247,12 @@ static int gup_pud_range(pgd_t pgd, unsigned long addr, unsigned long end,
> * Like get_user_pages_fast() except its IRQ-safe in that it won't fall
> * back to the regular GUP.
> */
> -int __get_user_pages_fast(unsigned long start, int nr_pages, int write,
> +int ___get_user_pages_fast(unsigned long start, int nr_pages, int flags,
> struct page **pages)
> {
> struct mm_struct *mm = current->mm;
> unsigned long addr, len, end;
> unsigned long next;
> - unsigned long flags;
> pgd_t *pgdp;
> int nr = 0;
>
> @@ -255,7 +260,7 @@ int __get_user_pages_fast(unsigned long start, int nr_pages, int write,
> addr = start;
> len = (unsigned long) nr_pages << PAGE_SHIFT;
> end = start + len;
> - if (unlikely(!access_ok(write ? VERIFY_WRITE : VERIFY_READ,
> + if (unlikely(!access_ok((flags & GUPF_WRITE) ? VERIFY_WRITE : VERIFY_READ,
> (void __user *)start, len)))
> return 0;
>
> @@ -277,7 +282,6 @@ int __get_user_pages_fast(unsigned long start, int nr_pages, int write,
> * (which we do on x86, with the above PAE exception), we can follow the
> * address down to the the page and take a ref on it.
> */
> - local_irq_save(flags);
> pgdp = pgd_offset(mm, addr);
> do {
> pgd_t pgd = *pgdp;
> @@ -285,14 +289,27 @@ int __get_user_pages_fast(unsigned long start, int nr_pages, int write,
> next = pgd_addr_end(addr, end);
> if (pgd_none(pgd))
> break;
> - if (!gup_pud_range(pgd, addr, next, write, pages, &nr))
> + if (!gup_pud_range(pgd, addr, next, flags, pages, &nr))
> break;
> } while (pgdp++, addr = next, addr != end);
> - local_irq_restore(flags);
>
> return nr;
> }
>
> +int __get_user_pages_fast(unsigned long start, int nr_pages, int write,
> + struct page **pages)
> +{
> + unsigned long flags;
> + int ret;
> +
> + local_irq_save(flags);
> + ret = ___get_user_pages_fast(start, nr_pages,
> + GUPF_GET | (write ? GUPF_WRITE : 0), pages);
> + local_irq_restore(flags);
> +
> + return ret;
> +}
> +
> /**
> * get_user_pages_fast() - pin user pages in memory
> * @start: starting user address
>


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