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Date: Thu, 3 Jun 2021 21:01:36 +0200
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Thread-Topic: rte_mempool_create conflicting parameter advice
Thread-Index: AddYquCyCVl+a57NSJijCcRof+hLaw==
From: =?iso-8859-1?Q?Morten_Br=F8rup?= <mb@smartsharesystems.com>
To: "Olivier Matz" <olivier.matz@6wind.com>,
 "Andrew Rybchenko" <andrew.rybchenko@oktetlabs.ru>
Cc: <dev@dpdk.org>
Subject: [dpdk-dev] rte_mempool_create conflicting parameter advice
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Olivier, Andrew (Memory pool maintainers)

While reviewing documentation for the parameters to =
rte_mempool_create(), I noticed these two conflicting recommendations:

1. n (the number of elements in the pool) is advised to be a power of =
two minus one.
2. cache_size is advised to have "n modulo cache_size =3D=3D 0".

E.g. n could be 0xFFFF, but then n modulo any value cannot be 0.


The cache_size parameter description tells what happens when not =
following the advice.

The n parameter description should also tell what happens when not =
following the advice.


Furthermore, the documentation for rte_pktmbuf_pool_create() and alike =
simply refer to the documentation for rte_mempool_create() regarding the =
cache_size parameter, although they copy the documentation regarding the =
n parameter. If the cache_size advice is important, it should be copied =
rather than simply referred to.