On Thu, Jul 28, 2016 at 02:59:45AM +0000, Mathieu Desnoyers wrote:
> ----- On Jul 27, 2016, at 11:05 AM, Boqun Feng boqun.feng@xxxxxxxxx wrote:
>
> > As rseq syscall is enabled on PPC, implement the self-tests on PPC to
> > verify the implementation of the syscall.
> >
> > Please note we only support 32bit userspace on BE kernel.
> >
> > Signed-off-by: Boqun Feng <boqun.feng@xxxxxxxxx>
> > ---
> > tools/testing/selftests/rseq/param_test.c | 14 ++++
> > tools/testing/selftests/rseq/rseq.h | 120 ++++++++++++++++++++++++++++++
> > 2 files changed, 134 insertions(+)
> >
> > diff --git a/tools/testing/selftests/rseq/param_test.c
> > b/tools/testing/selftests/rseq/param_test.c
> > index db25e0a818e5..e2cb1b165f81 100644
> > --- a/tools/testing/selftests/rseq/param_test.c
> > +++ b/tools/testing/selftests/rseq/param_test.c
> > @@ -75,6 +75,20 @@ static __thread unsigned int yield_mod_cnt, nr_retry;
> > "bne 222b\n\t" \
> > "333:\n\t"
> >
> > +#elif __PPC__
> > +#define INJECT_ASM_REG "r18"
> > +
> > +#define RSEQ_INJECT_CLOBBER \
> > + , INJECT_ASM_REG
> > +
> > +#define RSEQ_INJECT_ASM(n) \
> > + "lwz %%" INJECT_ASM_REG ", %[loop_cnt_" #n "]\n\t" \
> > + "cmpwi %%" INJECT_ASM_REG ", 0\n\t" \
> > + "beq 333f\n\t" \
> > + "222:\n\t" \
> > + "subic. %%" INJECT_ASM_REG ", %%" INJECT_ASM_REG ", 1\n\t" \
> > + "bne 222b\n\t" \
> > + "333:\n\t"
> > #else
> > #error unsupported target
> > #endif
> > diff --git a/tools/testing/selftests/rseq/rseq.h
> > b/tools/testing/selftests/rseq/rseq.h
> > index 791e14cf42ae..dea0bea52566 100644
> > --- a/tools/testing/selftests/rseq/rseq.h
> > +++ b/tools/testing/selftests/rseq/rseq.h
> > @@ -138,6 +138,35 @@ do { \
> > #define has_fast_acquire_release() 0
> > #define has_single_copy_load_64() 1
> >
> > +#elif __PPC__
> > +#define smp_mb() __asm__ __volatile__ ("sync" : : : "memory")
> > +#define smp_lwsync() __asm__ __volatile__ ("lwsync" : : : "memory")
> > +#define smp_rmb() smp_lwsync()
> > +#define smp_wmb() smp_lwsync()
> > +
> > +#define smp_load_acquire(p) \
> > +__extension__ ({ \
> > + __typeof(*p) ____p1 = READ_ONCE(*p); \
> > + smp_lwsync(); \
> > + ____p1; \
> > +})
> > +
> > +#define smp_acquire__after_ctrl_dep() smp_lwsync()
> > +
> > +#define smp_store_release(p, v) \
> > +do { \
> > + smp_lwsync(); \
> > + WRITE_ONCE(*p, v); \
> > +} while (0)
> > +
> > +#define has_fast_acquire_release() 1
>
> Can you check if defining has_fast_acquire_release() to 0 speeds up
> performance significantly ? It turns the smp_lwsync() into a
> compiler barrier() on the smp_load_acquire() side (fast-path), and
> turn the smp_lwsync() into a membarrier system call instead of the
> matching smp_store_release() (slow path).
>
Good point. Here are the numbers:
Power8 PSeries KVM Guest(64 VCPUs, the host has 16 cores, 128 hardware
threads):
Counter increment speed (ns/increment)
1 thread 2 threads 4 threads 8 threads 16 threads 32 threads
global increment (baseline) 6.5 N/A N/A N/A N/A N/A
percpu rseq increment 7.0 7.0 7.2 7.2 9.3 14.5
percpu rseq spinlock 18.5 18.5 18.6 18.8 25.5 52.7
So looks like defining has_fast_acquire_release() to 0 could benefit the
cases with more threads in current benchmark. I will send a updated
patch doing this.
And as discussed in IRC, I will also remove jump from rseq_finish()
fast-path in powerpc asm in the updated patch as you did for x86 and
ARM.
Regards,
Boqun
> Thanks,
>
> Mathieu
>
> > +
> > +# if __PPC64__
> > +# define has_single_copy_load_64() 1
> > +# else
> > +# define has_single_copy_load_64() 0
> > +# endif
> > +
> > #else
> > #error unsupported target
> > #endif
> > @@ -404,6 +433,97 @@ bool rseq_finish(struct rseq_lock *rlock,
> > : succeed
> > );
> > }
> > +#elif __PPC64__
> > + {
> > + /*
> > + * The __rseq_table section can be used by debuggers to better
> > + * handle single-stepping through the restartable critical
> > + * sections.
> > + */
> > + __asm__ __volatile__ goto (
> > + ".pushsection __rseq_table, \"aw\"\n\t"
> > + ".balign 8\n\t"
> > + "4:\n\t"
> > + ".quad 1f, 2f, 3f\n\t"
> > + ".popsection\n\t"
> > + "1:\n\t"
> > + RSEQ_INJECT_ASM(1)
> > + "lis %%r17, (4b)@highest\n\t"
> > + "ori %%r17, %%r17, (4b)@higher\n\t"
> > + "rldicr %%r17, %%r17, 32, 31\n\t"
> > + "oris %%r17, %%r17, (4b)@h\n\t"
> > + "ori %%r17, %%r17, (4b)@l\n\t"
> > + "std %%r17, 0(%[rseq_cs])\n\t"
> > + RSEQ_INJECT_ASM(2)
> > + "lwz %%r17, %[current_event_counter]\n\t"
> > + "li %%r16, 0\n\t"
> > + "cmpw cr7, %[start_event_counter], %%r17\n\t"
> > + "bne cr7, 3f\n\t"
> > + RSEQ_INJECT_ASM(3)
> > + "std %[to_write], 0(%[target])\n\t"
> > + "2:\n\t"
> > + RSEQ_INJECT_ASM(4)
> > + "std %%r16, 0(%[rseq_cs])\n\t"
> > + "b %l[succeed]\n\t"
> > + "3:\n\t"
> > + "li %%r16, 0\n\t"
> > + "std %%r16, 0(%[rseq_cs])\n\t"
> > + : /* no outputs */
> > + : [start_event_counter]"r"(start_value.event_counter),
> > + [current_event_counter]"m"(start_value.rseqp->abi.u.e.event_counter),
> > + [to_write]"r"(to_write),
> > + [target]"b"(p),
> > + [rseq_cs]"b"(&start_value.rseqp->abi.rseq_cs)
> > + RSEQ_INJECT_INPUT
> > + : "r16", "r17", "memory", "cc"
> > + RSEQ_INJECT_CLOBBER
> > + : succeed
> > + );
> > + }
> > +#elif __PPC__
> > + {
> > + /*
> > + * The __rseq_table section can be used by debuggers to better
> > + * handle single-stepping through the restartable critical
> > + * sections.
> > + */
> > + __asm__ __volatile__ goto (
> > + ".pushsection __rseq_table, \"aw\"\n\t"
> > + ".balign 8\n\t"
> > + "4:\n\t"
> > + ".long 0x0, 1f, 0x0, 2f, 0x0, 3f\n\t" /* 32 bit only supported on BE */
> > + ".popsection\n\t"
> > + "1:\n\t"
> > + RSEQ_INJECT_ASM(1)
> > + "lis %%r17, (4b)@ha\n\t"
> > + "addi %%r17, %%r17, (4b)@l\n\t"
> > + "stw %%r17, 0(%[rseq_cs])\n\t"
> > + RSEQ_INJECT_ASM(2)
> > + "lwz %%r17, %[current_event_counter]\n\t"
> > + "li %%r16, 0\n\t"
> > + "cmpw cr7, %[start_event_counter], %%r17\n\t"
> > + "bne cr7, 3f\n\t"
> > + RSEQ_INJECT_ASM(3)
> > + "stw %[to_write], 0(%[target])\n\t"
> > + "2:\n\t"
> > + RSEQ_INJECT_ASM(4)
> > + "stw %%r16, 0(%[rseq_cs])\n\t"
> > + "b %l[succeed]\n\t"
> > + "3:\n\t"
> > + "li %%r16, 0\n\t"
> > + "stw %%r16, 0(%[rseq_cs])\n\t"
> > + : /* no outputs */
> > + : [start_event_counter]"r"(start_value.event_counter),
> > + [current_event_counter]"m"(start_value.rseqp->abi.u.e.event_counter),
> > + [to_write]"r"(to_write),
> > + [target]"b"(p),
> > + [rseq_cs]"b"(&start_value.rseqp->abi.rseq_cs)
> > + RSEQ_INJECT_INPUT
> > + : "r16", "r17", "memory", "cc"
> > + RSEQ_INJECT_CLOBBER
> > + : succeed
> > + );
> > + }
> > #else
> > #error unsupported target
> > #endif
> > --
> > 2.9.0
>
> --
> Mathieu Desnoyers
> EfficiOS Inc.
> http://www.efficios.com
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