linux-kernel - Re: [PATCH net-next v5 01/14] page_pool: make sure frag API fields don't span between cachelines

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Message-ID: <b7e0e0f6-90e6-4fcf-9fe5-957d6a0864ca@intel.com>
Date:   Mon, 27 Nov 2023 15:12:29 +0100
From:   Alexander Lobakin <aleksander.lobakin@...el.com>
To:     Jakub Kicinski <kuba@...nel.org>
CC:     "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Paolo Abeni <pabeni@...hat.com>,
        Maciej Fijalkowski <maciej.fijalkowski@...el.com>,
        Michal Kubiak <michal.kubiak@...el.com>,
        Larysa Zaremba <larysa.zaremba@...el.com>,
        Alexander Duyck <alexanderduyck@...com>,
        Yunsheng Lin <linyunsheng@...wei.com>,
        "David Christensen" <drc@...ux.vnet.ibm.com>,
        Jesper Dangaard Brouer <hawk@...nel.org>,
        Ilias Apalodimas <ilias.apalodimas@...aro.org>,
        "Paul Menzel" <pmenzel@...gen.mpg.de>, <netdev@...r.kernel.org>,
        <intel-wired-lan@...ts.osuosl.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH net-next v5 01/14] page_pool: make sure frag API fields
 don't span between cachelines

From: Jakub Kicinski <kuba@...nel.org>
Date: Sun, 26 Nov 2023 14:54:57 -0800

> On Fri, 24 Nov 2023 16:47:19 +0100 Alexander Lobakin wrote:
>> -	long frag_users;
>> +	long frag_users __aligned(4 * sizeof(long));
> 
> A comment for the somewhat unusual alignment size would be good.

Roger that. Will paste a couple words from the commit message.

FYI, I had an idea of doing something like

__aligned(roundup_pow_of_2(2 * sizeof(long) + 2 * sizeof(int)))

but that looks horrible, so I stopped on the current :D There are no
functional changes between them either way.

Thanks,
Olek