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Wed, 30 Oct 2024 04:57:57 -0700 (PDT) X-Google-Smtp-Source: AGHT+IGVLgw5rE9QA3Icf5YbgX5jGmETg3oQl1odAk1S8jhHGqLiYvv6XcYW/kBL6ZHibuCo5cMEsg== X-Received: by 2002:a17:907:6d15:b0:a99:ecaf:4543 with SMTP id a640c23a62f3a-a9de5d8272dmr1567687166b.25.1730289476927; Wed, 30 Oct 2024 04:57:56 -0700 (PDT) Received: from alrua-x1.borgediget.toke.dk ([45.145.92.2]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-a9b1f2982e1sm568328366b.99.2024.10.30.04.57.56 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 30 Oct 2024 04:57:56 -0700 (PDT) Received: by alrua-x1.borgediget.toke.dk (Postfix, from userid 1000) id 49BAC164B390; Wed, 30 Oct 2024 12:57:55 +0100 (CET) From: Toke =?utf-8?Q?H=C3=B8iland-J=C3=B8rgensen?= To: Yunsheng Lin , Jesper Dangaard Brouer , davem@davemloft.net, kuba@kernel.org, pabeni@redhat.com Cc: zhangkun09@huawei.com, fanghaiqing@huawei.com, liuyonglong@huawei.com, Robin Murphy , Alexander Duyck , IOMMU , Andrew Morton , Eric Dumazet , Ilias Apalodimas , linux-mm@kvack.org, linux-kernel@vger.kernel.org, netdev@vger.kernel.org, kernel-team Subject: Re: [PATCH net-next v3 3/3] page_pool: fix IOMMU crash when driver has already unbound In-Reply-To: <1eac33ae-e8e1-4437-9403-57291ba4ced6@huawei.com> References: <20241022032214.3915232-1-linyunsheng@huawei.com> <20241022032214.3915232-4-linyunsheng@huawei.com> <113c9835-f170-46cf-92ba-df4ca5dfab3d@huawei.com> <878qudftsn.fsf@toke.dk> <87r084e8lc.fsf@toke.dk> <878qu7c8om.fsf@toke.dk> <1eac33ae-e8e1-4437-9403-57291ba4ced6@huawei.com> X-Clacks-Overhead: GNU Terry Pratchett Date: Wed, 30 Oct 2024 12:57:55 +0100 Message-ID: <87o731by64.fsf@toke.dk> MIME-Version: 1.0 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain X-Rspam-User: X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 8D77740013 X-Stat-Signature: y6tekftbx5ey63seci5izihtz5ft4r8z X-HE-Tag: 1730289446-477965 X-HE-Meta: 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 4AsrRcs5 iMQHgs5xpIfqk+Kv1GdDNwOOQx1XnIK4PPbakjMkqpw6f8yxLP+HBFsCVehE8X8Hexuks1TfCFSzYYJm3Sa7WA671cEG1GmzmbrPKAd93xJUk2jWBqsDVvv3XKzyCX+eTDZkVMRWsSMH0jbhNfc0N0FB677M/88rslVfgO5EvJ83MpOjwrIj9UlvUmlaRL/1iQumXGvAFNmv6LvxT6Xr3cWQAZC9JdfFusfelizgwDIudmETkm+7GACUHzY7h/fNeeerFb/iYdBXAq2GBmML3ZnXKOYgdCfUUXCkBOGm3Yo79jkB1BGBzOiXv4D2JoNRnxL8lRMTSlcjDnnZWVqVhaJ0I8jS+yPyk/RiCw+Jz6yLANG0gDEsVmliYph+Zna3gz2VYtJ/ycU7NnQ4J3DYvN/+TCGkzJ2vui6IcCBlK4xU0SG+dvd3pc3hbkNxFMc1A7z+y X-Bogosity: Ham, tests=bogofilter, spamicity=0.001799, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Yunsheng Lin writes: >> But, well, I'm not sure it is? You seem to be taking it as axiomatic >> that the wait in itself is bad. Why? It's just a bit memory being held >> on to while it is still in use, and so what? > > Actually, I thought about adding some sort of timeout or kicking based on > jakub's waiting patch too. > > But after looking at more caching in the networking, waiting and kicking/flushing > seems harder than recording the inflight pages, mainly because kicking/flushing > need very subsystem using page_pool owned page to provide a kicking/flushing > mechanism for it to work, not to mention how much time does it take to do all > the kicking/flushing. Eliding the details above, but yeah, you're right, there are probably some pernicious details to get right if we want to flush all caches. S I wouldn't do that to start with. Instead, just add the waiting to start with, then wait and see if this actually turns out to be a problem in practice. And if it is, identify the source of that problem, deal with it, rinse and repeat :) -Toke