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Message-ID: <20230502193309.382af41e@kernel.org> Date: Tue, 2 May 2023 19:33:09 -0700 From: Jakub Kicinski <kuba@...nel.org> To: Jesper Dangaard Brouer <brouer@...hat.com> Cc: Ilias Apalodimas <ilias.apalodimas@...aro.org>, netdev@...r.kernel.org, Eric Dumazet <eric.dumazet@...il.com>, linux-mm@...ck.org, Mel Gorman <mgorman@...hsingularity.net>, lorenzo@...nel.org, Toke Høiland-Jørgensen <toke@...hat.com>, linyunsheng@...wei.com, bpf@...r.kernel.org, "David S. Miller" <davem@...emloft.net>, Paolo Abeni <pabeni@...hat.com>, Andrew Morton <akpm@...ux-foundation.org>, willy@...radead.org Subject: Re: [PATCH RFC net-next/mm V3 1/2] page_pool: Remove workqueue in new shutdown scheme On Fri, 28 Apr 2023 18:16:19 +0200 Jesper Dangaard Brouer wrote: > This removes the workqueue scheme that periodically tests when > inflight reach zero such that page_pool memory can be freed. > > This change adds code to fast-path free checking for a shutdown flags > bit after returning PP pages. We can remove the warning without removing the entire delayed freeing scheme. I definitely like the SHUTDOWN flag and patch 2 but I'm a bit less clear on why the complexity of datapath freeing is justified. Can you explain? > Performance is very important for PP, as the fast path is used for > XDP_DROP use-cases where NIC drivers recycle PP pages directly into PP > alloc cache. > > This patch (since V3) shows zero impact on this fast path. Micro > benchmarked with [1] on Intel CPU E5-1650 @3.60GHz. The slight code > reorg of likely() are deliberate.
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