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b=CcF/cFqARf0VuUhI7Y/Pt9slkoRqLx674TxnSdmyHU/puzVrbNwnd3VXHJgeUa9W6 419nMt72rDHPd5p7sN1FkWntwtoHPMuFe5879CchUb3356LArWQPPU1HHywl/oIT6m NFvrmCv71j0R4VtxhZ5scVhEvD39MMx8U4gadelKRQdKHzBVLjjaX609KhW6vBiKa9 oKeYAxpU00syBdrNlI4hmPAXFUKbOftolNHzF7rTzWQ/wr1yo8qj5oefDFRyNOfGnE nzctTlDEXeE6bvAL+hqqJfE2SF2obHRaKUv/QTnULqqhNiLmfN6fsrZ0ls1JMezJLl xNHWza5UwVNIg== Date: Wed, 25 Mar 2026 14:10:23 +0000 From: "Lorenzo Stoakes (Oracle)" To: Vernon Yang Cc: "David Hildenbrand (Arm)" , akpm@linux-foundation.org, Wei Yang , lorenzo.stoakes@oracle.com, ziy@nvidia.com, dev.jain@arm.com, baohua@kernel.org, lance.yang@linux.dev, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Vernon Yang Subject: Re: [PATCH mm-new v8 2/4] mm: khugepaged: refine scan progress number Message-ID: <22dccc17-787c-448e-a571-23c7a9afeaff@lucifer.local> References: <20260221093918.1456187-1-vernon2gm@gmail.com> <20260221093918.1456187-3-vernon2gm@gmail.com> <20260224035247.r6mxsfcpiev4wnce@master> <1da56bbb-9211-42d7-9b08-3ee56d2b538d@kernel.org> <8a5277e0-d70e-4849-9763-ed90e350a118@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-Rspam-User: X-Rspamd-Queue-Id: 677C980011 X-Stat-Signature: mumyssfe6yy4wxncmxh4fhhwgw9r4hwf X-Rspamd-Server: rspam06 X-HE-Tag: 1774447827-405609 X-HE-Meta: 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 lurhvPPZ kKExPdPpzCI83LP48pB5YjqF+J+PWC2B0PSrZS32KZb4QPNDm+tP5RxW5lE+a0V7wEvdw4uE9O3B53+LVacDIXmpgP7Yy0EFl75UW6W2hmSGY89LXBsvhgZSkiMvlO3HR5SaQRhLpl0+yfC0WRIsLLeI8qbdtREwQ+owCmXoEM/K8aStHOTVntiHyd5mVSw+KQ4stB4hPC+V5HCIXGGmvudW5fgfxCvbU/4F1L97glJy5nSJXOt3d5Nu70LARrJUfXrkfLDO2edaV8AnkUJ02in1E+JbVi9Nm3L9/b0A9MLItWHSLG4Ndo2QxeJ6qlxFVakv0XCQoUGDDsnM= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Fri, Feb 27, 2026 at 01:15:24AM +0800, Vernon Yang wrote: > On Thu, Feb 26, 2026 at 11:45 PM David Hildenbrand (Arm) > wrote: > > > > On 2/26/26 15:31, Vernon Yang wrote: > > > On Wed, Feb 25, 2026 at 03:29:05PM +0100, David Hildenbrand (Arm) wrote: > > >> On 2/25/26 15:25, Vernon Yang wrote: > > >>> > > >>> Thank you for suggestion. > > >>> > > >>> Placing it inside "struct collapse_control" makes the overall code > > >>> simpler, there also coincidentally has a 4-bytes hole, as shown below: > > >>> > > >>> struct collapse_control { > > >>> bool is_khugepaged; /* 0 1 */ > > >>> > > >>> /* XXX 3 bytes hole, try to pack */ > > >>> > > >>> u32 node_load[64]; /* 4 256 */ > > >>> > > >>> /* XXX 4 bytes hole, try to pack */ > > >>> > > >>> /* --- cacheline 4 boundary (256 bytes) was 8 bytes ago --- */ > > >>> nodemask_t alloc_nmask; /* 264 8 */ > > >>> > > >>> /* size: 272, cachelines: 5, members: 3 */ > > >>> /* sum members: 265, holes: 2, sum holes: 7 */ > > >>> /* last cacheline: 16 bytes */ > > >>> }; > > >>> > > >>> But regardless of khugepaged or madvise(MADV_COLLAPSE), "cur_progress" > > >>> will be counted, while madvise(MADV_COLLAPSE) actually does not need to > > >>> be counted. > > >>> > > >>> David, do we want to place "cur_progress" inside the "struct collapse_control"? > > >> > > >> Might end up looking nicer code-wise. But the reset semantics (within a > > >> pmd) are a bit weird. > > >> > > >>> If Yes, it would be better to rename "cur_progress" to "pmd_progress", > > >>> as show below: > > >>> > > >> > > >> "pmd_progress" is misleading. "progress_in_pmd" might be clearer. > > >> > > >> Play with it to see if it looks better :) > > > > > > Hi Andrew, David, > > > > > > Based on previous discussions [1], v2 as follow, and testing shows the > > > same performance benefits. Just make code cleaner, no function changes. > > > > > > If David has no further revisions, Andrew, could you please squash the > > > following clean into this patch? If you prefer a new version, please let > > > me know. Thanks. > > > > Do we also have to update the resulting patch description? Patch itself > > LGTM. > > No need to update the patch description. I will take a look at this (sorry for delay) but general point - while fix-patches are convenient, they're incredibly anti-reviewer. I hope at some point in the future we can move away from that so you can look at a series on list and know that what's shown there is the actual patch. As it stands, I can't go line-by-line correctly here without quite a bit of additional effort. (Not a criticism of you Vernon just a general point about mm process). > > -- > Cheers, > Vernon Thanks, Lorenzo