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From: Pavan Nikhilesh Bhagavatula <pbhagavatula@marvell.com>
To: Harry van Haaren <harry.van.haaren@intel.com>,
	"dev@dpdk.org" <dev@dpdk.org>
Subject: Re: [dpdk-dev] [PATCH] eal: add new prefetch0_write variant
Date: Sun, 13 Sep 2020 20:11:08 +0000
Message-ID: <BN6PR18MB11402D4A8AB0E722D902D3BFDE220@BN6PR18MB1140.namprd18.prod.outlook.com> (raw)
In-Reply-To: <20200911091919.62167-1-harry.van.haaren@intel.com>

>This commit adds a new rte_prefetch0_write() variant, suggests to the
>compiler to use a prefetch instruction with intention to write. As a
>compiler builtin, the compiler can choose based on compilation target
>what the best implementation for this instruction is.	

Why not have the other variants too i.e. l2/l3/temporal store prefetches too?


>
>Signed-off-by: Harry van Haaren <harry.van.haaren@intel.com>
>
>---
>
>The integer constants passed to the builtin are not available as
>a #define value, and doing #defines just for this write variant
>does not seems a nice solution to me... particularly for those using
>IDEs where any #define value is auto-hinted for code-completion.
>
>---
> lib/librte_eal/include/generic/rte_prefetch.h | 16 ++++++++++++++++
> 1 file changed, 16 insertions(+)
>
>diff --git a/lib/librte_eal/include/generic/rte_prefetch.h
>b/lib/librte_eal/include/generic/rte_prefetch.h
>index 6e47bdfbad..44e2e9abfc 100644
>--- a/lib/librte_eal/include/generic/rte_prefetch.h
>+++ b/lib/librte_eal/include/generic/rte_prefetch.h
>@@ -51,4 +51,20 @@ static inline void rte_prefetch2(const volatile
>void *p);
>  */
> static inline void rte_prefetch_non_temporal(const volatile void *p);
>
>+/**
>+ * Prefetch a cache line into all cache levels, with intention to write.
>This
>+ * prefetch variant hints to the CPU that the program is expecting to
>write to
>+ * the cache line being prefetched.
>+ *
>+ * @param p Address to prefetch
>+ */
>+static inline void rte_prefetch0_write(const void *p)
>+{
>+	/* 1 indicates intention to write, 3 sets target cache level to L1.
>See
>+	 * GCC docs where these integer constants are described in
>more detail:
>+	 *  https://urldefense.proofpoint.com/v2/url?u=https-
>3A__gcc.gnu.org_onlinedocs_gcc_Other-
>2DBuiltins.html&d=DwIBAg&c=nKjWec2b6R0mOyPaz7xtfQ&r=1cjuAHrG
>h745jHNmj2fD85sUMIJ2IPIDsIJzo6FN6Z0&m=OMPc_t21vsWlzVl0UjdGB
>hTTv1Gngqfk8vth9UQtUSA&s=51jgfiV2UC5B3xxBE-
>4gRAte3lCZP3v370U7Fpn6LaE&e=
>+	 */
>+	__builtin_prefetch(p, 1, 3);
>+}
>+
> #endif /* _RTE_PREFETCH_H_ */
>--
>2.17.1


  reply	other threads:[~2020-09-13 20:11 UTC|newest]

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-09-11  9:19 Harry van Haaren
2020-09-13 20:11 ` Pavan Nikhilesh Bhagavatula [this message]
2020-09-14  8:12   ` Van Haaren, Harry
2020-09-14 10:39     ` Pavan Nikhilesh Bhagavatula
2020-09-14 15:10       ` Van Haaren, Harry
2020-09-14 15:10 ` [dpdk-dev] [PATCH v2] eal: add new prefetch write variants Harry van Haaren
2020-10-08  7:42   ` David Marchand
2020-10-08  8:34     ` Van Haaren, Harry
2020-10-08  8:39       ` Van Haaren, Harry
2020-10-08  8:54   ` Jerin Jacob
2020-10-10 10:21   ` Ruifeng Wang
2020-10-15  8:18   ` David Marchand
2020-10-15  8:44     ` Van Haaren, Harry
2020-10-15 10:32   ` [dpdk-dev] [PATCH v3] " Harry van Haaren
2020-10-15 20:27     ` David Marchand

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