netdev - Re: [PATCH net] openvswitch: Allocate struct ovs_pcpu

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Message-ID: <20250616150902.330c4ac3@kernel.org>
Date: Mon, 16 Jun 2025 15:09:02 -0700
From: Jakub Kicinski <kuba@...nel.org>
To: Sebastian Andrzej Siewior <bigeasy@...utronix.de>, Gal Pressman
 <gal@...dia.com>
Cc: netdev@...r.kernel.org, dev@...nvswitch.org, "David S. Miller"
 <davem@...emloft.net>, Aaron Conole <aconole@...hat.com>, Eelco Chaudron
 <echaudro@...hat.com>, Eric Dumazet <edumazet@...gle.com>, Ilya Maximets
 <i.maximets@....org>, Paolo Abeni <pabeni@...hat.com>, Simon Horman
 <horms@...nel.org>
Subject: Re: [PATCH net] openvswitch: Allocate struct ovs_pcpu_storage
 dynamically

On Fri, 13 Jun 2025 14:36:29 +0200 Sebastian Andrzej Siewior wrote:
> PERCPU_MODULE_RESERVE defines the maximum size that can by used for the
> per-CPU data size used by modules. This is 8KiB.
> 
> Commit 035fcdc4d240c ("openvswitch: Merge three per-CPU structures into
> one") restructured the per-CPU memory allocation for the module and
> moved the separate alloc_percpu() invocations at module init time to a
> static per-CPU variable which is allocated by the module loader.

IIUC you're saying that the module loader only gets 8kB but dynamic
allocations from the code don't have this restriction?
Maybe just me but TBH the commit message reads like the inverse :S

> The size of the per-CPU data section for openvswitch is 6488 bytes which
> is ~80% of the available per-CPU memory. Together with a few other
> modules it is easy to exhaust the available 8KiB of memory.
> 
> Allocate ovs_pcpu_storage dynamically at module init time.

Gal, should we wait for your testing or apply?