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From: Thomas Monjalon <thomas@monjalon.net>
To: "Morten Brørup" <mb@smartsharesystems.com>
Cc: david.marchand@redhat.com, honnappa.nagarahalli@arm.com,
	konstantin.v.ananyev@yandex.ru, bruce.richardson@intel.com,
	mattias.ronnblom@ericsson.com, dev@dpdk.org,
	olivier.matz@6wind.com, andrew.rybchenko@oktetlabs.ru,
	dev@dpdk.org
Subject: Re: [PATCH] clarify purpose of empty cache lines
Date: Thu, 12 Oct 2023 01:43:44 +0200	[thread overview]
Message-ID: <6554142.G0QQBjFxQf@thomas> (raw)
In-Reply-To: <20230904084349.12044-1-mb@smartsharesystems.com>

04/09/2023 10:43, Morten Brørup:
>  /** Force minimum cache line alignment. */
>  #define __rte_cache_min_aligned __rte_aligned(RTE_CACHE_LINE_MIN_SIZE)
>  
> +#define _RTE_CACHE_GUARD_HELPER2(unique) \
> +		char cache_guard_ ## unique[RTE_CACHE_LINE_SIZE * RTE_CACHE_GUARD_LINES] \
> +		__rte_cache_aligned
> +#define _RTE_CACHE_GUARD_HELPER1(unique) _RTE_CACHE_GUARD_HELPER2(unique)

What is the reason for this intermediate helper macro?

> +/**
> + * Empty cache lines, to guard against false sharing-like effects
> + * on systems with a next-N-lines hardware prefetcher.
> + *
> + * Use as spacing between data accessed by different lcores,
> + * to prevent cache thrashing on hardware with speculative prefetching.
> + */
> +#define RTE_CACHE_GUARD _RTE_CACHE_GUARD_HELPER1(__COUNTER__)





  parent reply	other threads:[~2023-10-11 23:43 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-09-04  8:43 Morten Brørup
2023-09-04  9:12 ` Bruce Richardson
2023-10-11 15:59   ` Thomas Monjalon
2023-09-05  6:41 ` Morten Brørup
2023-10-11 23:43 ` Thomas Monjalon [this message]
2023-10-12  6:00   ` Morten Brørup
2023-10-12  6:07   ` Morten Brørup

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