On Apr 24, 2014, at 5:55 PM, Ethan Jackson <et...@nicira.com> wrote:
> I think there should be a comment explaining when to use prefetch vs
> prefetch_write. I certainly don't know off the top of my head.
>
I wrote this based on GCC documentation:
/* OVS_PREFETCH() can be used to instruct the CPU to fetch the cache
* line containing the given address to a CPU cache.
* OVS_PREFETCH_WRITE() should be used when the memory is going to be
* written to. Depending on the target CPU, this can generate the same
* instruction as OVS_PREFETCH(), or bring the data into the cache in an
* exclusive state. */
> Acked-by: Ethan Jackson <et...@nicira.com>
>
Thanks,
Jarno
>
> On Fri, Apr 18, 2014 at 12:41 PM, Jarno Rajahalme <jrajaha...@nicira.com>
> wrote:
>> Define OVS_PREFETCH() and OVS_PREFETCH_WRITE() using builtin prefetch
>> for GCC, and ovs_prefetch_range() for prefetching a range of addresses.
>>
>> Signed-off-by: Jarno Rajahalme <jrajaha...@nicira.com>
>> ---
>> lib/compiler.h | 8 ++++++++
>> lib/util.h | 14 ++++++++++++++
>> 2 files changed, 22 insertions(+)
>>
>> diff --git a/lib/compiler.h b/lib/compiler.h
>> index 3b59813..981605c 100644
>> --- a/lib/compiler.h
>> +++ b/lib/compiler.h
>> @@ -206,4 +206,12 @@
>> static void f(void)
>> #endif
>>
>> +#if __GNUC__
>> +#define OVS_PREFETCH(addr) __builtin_prefetch((addr))
>> +#define OVS_PREFETCH_WRITE(addr) __builtin_prefetch((addr), 1)
>> +#else
>> +#define OVS_PREFETCH(addr)
>> +#define OVS_PREFETCH_WRITE(addr)
>> +#endif
>> +
>> #endif /* compiler.h */
>> diff --git a/lib/util.h b/lib/util.h
>> index aff17a5..5c3668a 100644
>> --- a/lib/util.h
>> +++ b/lib/util.h
>> @@ -151,6 +151,19 @@ is_pow2(uintmax_t x)
>> #define CACHE_LINE_SIZE 64
>> BUILD_ASSERT_DECL(IS_POW2(CACHE_LINE_SIZE));
>>
>> +#define CACHE_LINE_SIZE 64 /* Correct for most CPUs. */
>> +
>> +static inline void
>> +ovs_prefetch_range(const void *start, size_t size)
>> +{
>> + const char *addr = (const char *)start;
>> + size_t ofs;
>> +
>> + for (ofs = 0; ofs < size; ofs += CACHE_LINE_SIZE) {
>> + OVS_PREFETCH(addr + ofs);
>> + }
>> +}
>> +
>> #ifndef MIN
>> #define MIN(X, Y) ((X) < (Y) ? (X) : (Y))
>> #endif
>> @@ -503,6 +516,7 @@ uint64_t bitwise_get(const void *src, unsigned int
>> src_len,
>> unsigned int src_ofs, unsigned int n_bits);
>>
>> void xsleep(unsigned int seconds);
>> +
>> #ifdef _WIN32
>>
>> char *ovs_format_message(int error);
>> --
>> 1.7.10.4
>>
>> _______________________________________________
>> dev mailing list
>> dev@openvswitch.org
>> http://openvswitch.org/mailman/listinfo/dev
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