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Date: Thu, 26 Feb 2026 08:56:43 -0800
From: Jakub Kicinski <kuba@kernel.org>
To: Nimrod Oren <noren@nvidia.com>
Cc: Jesper Dangaard Brouer <hawk@kernel.org>, Ilias Apalodimas
 <ilias.apalodimas@linaro.org>, "David S. Miller" <davem@davemloft.net>,
 Eric Dumazet <edumazet@google.com>, Paolo Abeni <pabeni@redhat.com>, Simon
 Horman <horms@kernel.org>, netdev@vger.kernel.org,
 linux-kernel@vger.kernel.org, Gal Pressman <gal@nvidia.com>, Dragos Tatulea
 <dtatulea@nvidia.com>, Tariq Toukan <tariqt@nvidia.com>
Subject: Re: [RFC net-next] net: page_pool: cap alloc cache size and refill
 by pool ring size
Message-ID: <20260226085643.20b9f256@kernel.org>
In-Reply-To: <03b14f08-bb37-4130-b81c-6993ff406df0@nvidia.com>
References: <20260223092410.2149014-1-noren@nvidia.com>
	<20260224153959.377a8e32@kernel.org>
	<03b14f08-bb37-4130-b81c-6993ff406df0@nvidia.com>
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On Thu, 26 Feb 2026 17:28:55 +0200 Nimrod Oren wrote:
> On 25/02/2026 1:39, Jakub Kicinski wrote:
> > I'd simply change the defines based on PAGE_SIZE. The allocation batch
> > size has nothing to do with the ring size, it's just amortizing
> > allocations within a single NAPI cycle.  
> 
> Thanks, that sounds good to me.
> Do you think a formula like this would work?
> 
> #define PP_ALLOC_CACHE_REFILL ((64 * SZ_4K) / PAGE_SIZE)
> #define PP_ALLOC_CACHE_SIZE   (PP_ALLOC_CACHE_REFILL * 2)
> 
> It keeps both values constant in bytes across page sizes, ensuring a
> consistent memory footprint for pool alloc-caches regardless of a
> system's page size.

I like the clarity / obviousness of the if/elif/else list. 
No need to think what the result would be for a given page size. 
But up to you.