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From: Thomas Monjalon <thomas@monjalon.net>
To: "Morten Brørup" <mb@smartsharesystems.com>
Cc: olivier.matz@6wind.com, andrew.rybchenko@oktetlabs.ru,
	dev@dpdk.org, jerinj@marvell.com, bruce.richardson@intel.com,
	dev@dpdk.org
Subject: Re: [PATCH v4 1/2] mempool: cache align mempool cache objects
Date: Sun, 30 Oct 2022 10:17:49 +0100	[thread overview]
Message-ID: <2285151.n0HT0TaD9V@thomas> (raw)
In-Reply-To: <20221028064152.98341-1-mb@smartsharesystems.com>

28/10/2022 08:41, Morten Brørup:
> Add __rte_cache_aligned to the objs array.
> 
> It makes no difference in the general case, but if get/put operations are
> always 32 objects, it will reduce the number of memory (or last level
> cache) accesses from five to four 64 B cache lines for every get/put
> operation.
> 
> For readability reasons, an example using 16 objects follows:
> 
> Currently, with 16 objects (128B), we access to 3
> cache lines:
> 
>       ┌────────┐
>       │len     │
> cache │********│---
> line0 │********│ ^
>       │********│ |
>       ├────────┤ | 16 objects
>       │********│ | 128B
> cache │********│ |
> line1 │********│ |
>       │********│ |
>       ├────────┤ |
>       │********│_v_
> cache │        │
> line2 │        │
>       │        │
>       └────────┘
> 
> With the alignment, it is also 3 cache lines:
> 
>       ┌────────┐
>       │len     │
> cache │        │
> line0 │        │
>       │        │
>       ├────────┤---
>       │********│ ^
> cache │********│ |
> line1 │********│ |
>       │********│ |
>       ├────────┤ | 16 objects
>       │********│ | 128B
> cache │********│ |
> line2 │********│ |
>       │********│ v
>       └────────┘---
> 
> However, accessing the objects at the bottom of the mempool cache is a
> special case, where cache line0 is also used for objects.
> 
> Consider the next burst (and any following bursts):
> 
> Current:
>       ┌────────┐
>       │len     │
> cache │        │
> line0 │        │
>       │        │
>       ├────────┤
>       │        │
> cache │        │
> line1 │        │
>       │        │
>       ├────────┤
>       │        │
> cache │********│---
> line2 │********│ ^
>       │********│ |
>       ├────────┤ | 16 objects
>       │********│ | 128B
> cache │********│ |
> line3 │********│ |
>       │********│ |
>       ├────────┤ |
>       │********│_v_
> cache │        │
> line4 │        │
>       │        │
>       └────────┘
> 4 cache lines touched, incl. line0 for len.
> 
> With the proposed alignment:
>       ┌────────┐
>       │len     │
> cache │        │
> line0 │        │
>       │        │
>       ├────────┤
>       │        │
> cache │        │
> line1 │        │
>       │        │
>       ├────────┤
>       │        │
> cache │        │
> line2 │        │
>       │        │
>       ├────────┤
>       │********│---
> cache │********│ ^
> line3 │********│ |
>       │********│ | 16 objects
>       ├────────┤ | 128B
>       │********│ |
> cache │********│ |
> line4 │********│ |
>       │********│_v_
>       └────────┘
> Only 3 cache lines touched, incl. line0 for len.
> 
> Credits go to Olivier Matz for the nice ASCII graphics.
> 
> v4:
> * No changes. Added reviewed- and acked-by tags.
> v3:
> * No changes. Made part of a series.
> v2:
> * No such version.
> 
> Signed-off-by: Morten Brørup <mb@smartsharesystems.com>
> Reviewed-by: Andrew Rybchenko <andrew.rybchenko@oktetlabs.ru>
> Acked-by: Olivier Matz <olivier.matz@6wind.com>

Applied only this first patch, thanks.
The second patch needs more time.

      parent reply	other threads:[~2022-10-30  9:17 UTC|newest]

Thread overview: 85+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-12-26 15:34 [RFC] mempool: rte_mempool_do_generic_get optimizations Morten Brørup
2022-01-06 12:23 ` [PATCH] mempool: optimize incomplete cache handling Morten Brørup
2022-01-06 16:55   ` Jerin Jacob
2022-01-07  8:46     ` Morten Brørup
2022-01-10  7:26       ` Jerin Jacob
2022-01-10 10:55         ` Morten Brørup
2022-01-14 16:36 ` [PATCH] mempool: fix get objects from mempool with cache Morten Brørup
2022-01-17 17:35   ` Bruce Richardson
2022-01-18  8:25     ` Morten Brørup
2022-01-18  9:07       ` Bruce Richardson
2022-01-24 15:38   ` Olivier Matz
2022-01-24 16:11     ` Olivier Matz
2022-01-28 10:22     ` Morten Brørup
2022-01-17 11:52 ` [PATCH] mempool: optimize put objects to " Morten Brørup
2022-01-19 14:52 ` [PATCH v2] mempool: fix " Morten Brørup
2022-01-19 15:03 ` [PATCH v3] " Morten Brørup
2022-01-24 15:39   ` Olivier Matz
2022-01-28  9:37     ` Morten Brørup
2022-02-02  8:14 ` [PATCH v2] mempool: fix get objects from " Morten Brørup
2022-06-15 21:18   ` Morten Brørup
2022-09-29 10:52     ` Morten Brørup
2022-10-04 12:57   ` Andrew Rybchenko
2022-10-04 15:13     ` Morten Brørup
2022-10-04 15:58       ` Andrew Rybchenko
2022-10-04 18:09         ` Morten Brørup
2022-10-06 13:43       ` Aaron Conole
2022-10-04 16:03   ` Morten Brørup
2022-10-04 16:36   ` Morten Brørup
2022-10-04 16:39   ` Morten Brørup
2022-02-02 10:33 ` [PATCH v4] mempool: fix mempool cache flushing algorithm Morten Brørup
2022-04-07  9:04   ` Morten Brørup
2022-04-07  9:14     ` Bruce Richardson
2022-04-07  9:26       ` Morten Brørup
2022-04-07 10:32         ` Bruce Richardson
2022-04-07 10:43           ` Bruce Richardson
2022-04-07 11:36             ` Morten Brørup
2022-10-04 20:01   ` Morten Brørup
2022-10-09 11:11   ` [PATCH 1/2] mempool: check driver enqueue result in one place Andrew Rybchenko
2022-10-09 11:11     ` [PATCH 2/2] mempool: avoid usage of term ring on put Andrew Rybchenko
2022-10-09 13:08       ` Morten Brørup
2022-10-09 13:14         ` Andrew Rybchenko
2022-10-09 13:01     ` [PATCH 1/2] mempool: check driver enqueue result in one place Morten Brørup
2022-10-09 13:19   ` [PATCH v4] mempool: fix mempool cache flushing algorithm Andrew Rybchenko
2022-10-04 12:53 ` [PATCH v3] mempool: fix get objects from mempool with cache Andrew Rybchenko
2022-10-04 14:42   ` Morten Brørup
2022-10-07 10:44 ` [PATCH v4] " Andrew Rybchenko
2022-10-08 20:56   ` Thomas Monjalon
2022-10-11 20:30     ` Copy-pasted code should be updated Morten Brørup
2022-10-11 21:47       ` Honnappa Nagarahalli
2022-10-30  8:44         ` Morten Brørup
2022-10-30 22:50           ` Honnappa Nagarahalli
2022-10-14 14:01     ` [PATCH v4] mempool: fix get objects from mempool with cache Olivier Matz
2022-10-09 13:37 ` [PATCH v6 0/4] mempool: fix mempool cache flushing algorithm Andrew Rybchenko
2022-10-09 13:37   ` [PATCH v6 1/4] mempool: check driver enqueue result in one place Andrew Rybchenko
2022-10-09 13:37   ` [PATCH v6 2/4] mempool: avoid usage of term ring on put Andrew Rybchenko
2022-10-09 13:37   ` [PATCH v6 3/4] mempool: fix cache flushing algorithm Andrew Rybchenko
2022-10-09 14:31     ` Morten Brørup
2022-10-09 14:51       ` Andrew Rybchenko
2022-10-09 15:08         ` Morten Brørup
2022-10-14 14:01           ` Olivier Matz
2022-10-14 15:57             ` Morten Brørup
2022-10-14 19:50               ` Olivier Matz
2022-10-15  6:57                 ` Morten Brørup
2022-10-18 16:32                   ` Jerin Jacob
2022-10-09 13:37   ` [PATCH v6 4/4] mempool: flush cache completely on overflow Andrew Rybchenko
2022-10-09 14:44     ` Morten Brørup
2022-10-14 14:01       ` Olivier Matz
2022-10-10 15:21   ` [PATCH v6 0/4] mempool: fix mempool cache flushing algorithm Thomas Monjalon
2022-10-11 19:26     ` Morten Brørup
2022-10-26 14:09     ` Thomas Monjalon
2022-10-26 14:26       ` Morten Brørup
2022-10-26 14:44         ` [PATCH] mempool: cache align mempool cache objects Morten Brørup
2022-10-26 19:44           ` Andrew Rybchenko
2022-10-27  8:34           ` Olivier Matz
2022-10-27  9:22             ` Morten Brørup
2022-10-27 11:42               ` Olivier Matz
2022-10-27 12:11                 ` Morten Brørup
2022-10-27 15:20                   ` Olivier Matz
2022-10-28  6:35           ` [PATCH v3 1/2] " Morten Brørup
2022-10-28  6:35             ` [PATCH v3 2/2] mempool: optimized debug statistics Morten Brørup
2022-10-28  6:41           ` [PATCH v4 1/2] mempool: cache align mempool cache objects Morten Brørup
2022-10-28  6:41             ` [PATCH v4 2/2] mempool: optimized debug statistics Morten Brørup
2022-10-30  9:09               ` Morten Brørup
2022-10-30  9:16                 ` Thomas Monjalon
2022-10-30  9:17             ` Thomas Monjalon [this message]

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