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Fri, 24 Apr 2020 13:16:45 +0900 (KST) Received: from [10.253.104.82] (unknown [10.253.104.82]) by epsmtip2.samsung.com (KnoxPortal) with ESMTPA id 20200424041645epsmtip2baa9db0282471f5ef5465d9d636ebe36~IpmE7sZXO2398923989epsmtip2f; Fri, 24 Apr 2020 04:16:45 +0000 (GMT) Subject: Re: [PATCH v2] mm/vmscan: count layzfree pages and fix nr_isolated_* mismatch To: Minchan Kim , Johannes Weiner Cc: mgorman@suse.de, m.szyprowski@samsung.com, mina86@mina86.com, shli@fb.com, akpm@linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, jaewon31.kim@gmail.com, ytk.lee@samsung.com From: Jaewon Kim Message-ID: <5EA2682D.7010307@samsung.com> Date: Fri, 24 Apr 2020 13:16:45 +0900 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.7.2 MIME-Version: 1.0 In-Reply-To: <20200423200020.GB46847@google.com> X-Brightmail-Tracker: H4sIAAAAAAAAA01TaUwTURD2ddvugtas9ZoQj7qoBAzQWltWI8ZEootXSDTGaAJuYG3RXnYL gncCnqCIoIEiBpUQRaTQqoEGNQJGFK8ACV6oRCWKAgoBUVRsuxj5N/PN930zb957BCa/Kw0g Ek02zmpiDZTUX3yjLjg0NEx/IVb5qGgCfdZRJqWvONfQGa58RDe7z0rp12XDEvpqfRtO53R3 ILroXrqELunvwemS6iwx/c4xdulYpu5LD8Zkp3XjTLW9DWecpUeljLP3FM405A2JmfJfnSLm xLVSxLgadzN9zhkx/psMi/Ucm8BZFZwp3pyQaNJFUqvWxS2L02iVqlDVQjqCUphYIxdJRa2O CV2eaPAMTCmSWUOSB4pheZ4KX7LYak6ycQq9mbdFUpwlwWBRKS1hPGvkk0y6sHizcZFKqZyv 8TC3GPS5JZW45TGZUpOuPYCuy44hPwLIBZD79anoGPIn5GQVgrLa1pGkF0HumQyxkPQhKLh4 TvJP8uRwPRIKbgSDdqdUSLoQvBgsFXlZE8mNMHDkJuaNJ5Eroe/SZYmXhJGNCMofvhR7C1Jy HvQUnfLZysgQyOnK9gnE5ByoKXb48Mkeo6rCb0jgTID7+e89WoLwI5VwsmCHF8bImZB2vQDz +gNZQ0DW4RzMywEyCjq/i4SpJ0LnvWu4EAfAp6xDuMBPQ9CV70JCko6gzXkcCSw1HM986jPC yGBwuMMFeBZUDxUiofF46O7PlAi9ZHDkkFygzIX0jv6RbU2D3386RmIGulvvSIRlFYvA1fAF O4kU9lFHs486j/1/5yKElaIpnIU36jheZVGPvmIn8j3hkIgqVPF4dS0iCUSNkz2zno+VS9hk PtVYi4DAqEmyivZzsXJZApu6i7Oa46xJBo6vRRrPtrOxgMnxZs+HMNniVJr5arWaXqCN0GrU 1FTZ6VZDrJzUsTZuO8dZOOs/nYjwCziA1m7rndt+pzklJrDwW2dxXtStrRXszpSKD/IlWFCH YiCzIfXKg8p5f16t29uSt2ra+6FNKYF6XfGPlrfJz29/LF+eHDTl52DBQOPd6M+ze6O1TeFv BlaYMtyS6U3y+13PtHkz7W5XRMv6PZuDsKYxQ1fzHcP77VvpdnwDtnT4YOC+H82UmNezqhDM yrN/AUskxOLYAwAA X-Brightmail-Tracker: H4sIAAAAAAAAA+NgFmpnkeLIzCtJLcpLzFFi42LZdlhJXlc3Y1GcQft3WYs569ewWaze5GvR vXkmo8XlXXPYLO6t+c9qsfbIXXaLye+eMVosON7CarHs63t2i2U7+1ksHq/nduD2OPzmPbPH xOZ37B47Z91l99i0qpPNY9OnSeweJ2b8ZvFY9+cVk0ffllWMHptPV3t83iQXwBXFZZOSmpNZ llqkb5fAlTFl2Ub2gnMCFXtazBoYt/J2MXJySAiYSJxvP8IIYgsJ7GCUmPdFESIuI/Hm/FOW LkYOIFtY4vDh4i5GLqCS14wSL6e9ZQKpERaIkLj17SI7iC0i4CXxecVKVoiiJUwSJ190MII4 zAKnGSVmtV1hBaliE9CWeL9gEpjNK6AlMfntRGYQm0VAVWLPkvVgcVGgqavXXWOGqBGUODnz CdgVnAIGEhNmF4KEmQXUJf7Mu8QMYctLNG+dzTyBUXAWko5ZSMpmISlbwMi8ilEytaA4Nz23 2LDAKC+1XK84Mbe4NC9dLzk/dxMjOK60tHYw7ln1Qe8QIxMH4yFGCQ5mJRHeDQ/nxQnxpiRW VqUW5ccXleakFh9ilOZgURLn/TprYZyQQHpiSWp2ampBahFMlomDU6qBKaulluPI1Wm5R3/p CfPymiwRXX8hMYj7t7iL5yaWGYnsX+8o8J9g1z+7Z6e/zsv7H36fXWioOun5CyXrYvkI+6kc 7z6mXTsR7zr39ktBDS+2mRPLls87frk+h7Nf5v/nTIFwDsdV56dJ7Ilb0cbqKdz7Zcf3PC2u np31D2bZOs1gOFv2w+CqyNvoNNFM78bc62EVsx9zTW2/vb5aS/J0NN/5goRlntnbU5pn6n5J Oap/wjTg+p/DkbuPirYXV87Vyt1gy2e0j/9uwkEvWQ7nvZqs7HOsgleYC1dqqmo7f2xZuqD7 5+9zy9sPzE0wuvX+ddD5V17zVAMjtiVmlck8ZuP/v3bV2vvdRhLZR57MVWIpzkg01GIuKk4E AC52eCkaAwAA X-CMS-MailID: 20200424041645epcas1p2e5d0c132ebae47d7f6d60d33bf920712 X-Msg-Generator: CA Content-Type: text/plain; charset="utf-8" X-Sendblock-Type: SVC_REQ_APPROVE CMS-TYPE: 101P DLP-Filter: Pass X-CFilter-Loop: Reflected X-CMS-RootMailID: 20200422084832epcas1p333225f9b6a00c9ce36f5f5d63fe6e3bf References: <20200422084815.21913-1-jaewon31.kim@samsung.com> <20200422130751.GD358439@cmpxchg.org> <5EA10872.3010500@samsung.com> <20200423160546.GA389168@cmpxchg.org> <20200423200020.GB46847@google.com> Content-Transfer-Encoding: quoted-printable X-Bogosity: Ham, tests=bogofilter, spamicity=0.000002, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 2020=EB=85=84 04=EC=9B=94 24=EC=9D=BC 05:00, Minchan Kim wrote: > On Thu, Apr 23, 2020 at 12:05:46PM -0400, Johannes Weiner wrote: >> On Thu, Apr 23, 2020 at 12:16:02PM +0900, Jaewon Kim wrote: >>> >>> On 2020=EB=85=84 04=EC=9B=94 22=EC=9D=BC 22:07, Johannes Weiner wrote= : >>>> On Wed, Apr 22, 2020 at 05:48:15PM +0900, Jaewon Kim wrote: >>>>> @@ -1295,11 +1295,15 @@ static unsigned long shrink_page_list(struc= t list_head *page_list, >>>>> */ >>>>> if (page_mapped(page)) { >>>>> enum ttu_flags flags =3D ttu_flags | TTU_BATCH_FLUSH; >>>>> + bool lazyfree =3D PageAnon(page) && !PageSwapBacked(page); >>>>> =20 >>>>> if (unlikely(PageTransHuge(page))) >>>>> flags |=3D TTU_SPLIT_HUGE_PMD; >>>>> + >>>>> if (!try_to_unmap(page, flags)) { >>>>> stat->nr_unmap_fail +=3D nr_pages; >>>>> + if (lazyfree && PageSwapBacked(page)) >>>> This looks pretty strange, until you remember that try_to_unmap() >>>> could SetPageSwapbacked again. >>>> >>>> This might be more obvious? >>>> >>>> was_swapbacked =3D PageSwapBacked(page); >>>> if (!try_to_unmap(page, flags)) { >>>> stat->nr_unmap_fail +=3D nr_pages; >>>> if (!was_swapbacked && PageSwapBacked(page)) >>> Hello Johannes, thank you for your comment. >>> >>> The name can changed from layzyfree to was_swapbacked. >>> By the way, did you mean removing PageAnon(page), too? It seems to be= OK, though. >> I can't decide whether PageAnon() makes it clearer or not. But it's >> not really needed for correctness. So feel free to keep what you had. > Yub, PageAnon is redundant. > >> I would really just at least change bool lazyfree to was_lazyfree, > It's better. Thank you both. Sorry but let me ask again. Because PageAnon is redundant, let me remove it on checking lazyfree. Then, I think, was_swapbacked (first suggestion) is better then was_lazyf= ree (second suggestion), because it just checks PageSwapBacked(page). And we knows was_swapbacked = is used for lazyfree on stat->nr_lazyfree_fail. If you don't mind let me pick was_swapbacked instead of was_lazyfree bool was_lazyfree =3D PageSwapBacked(page); Thank you > >