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b=OdMSTtrEFg4+AGBw878XaR6uOAeNGvy/8yLqfJgPzBcEDzZ5fp6NaaNoMwboYXmJ1 7txHfU9adWdlrfIaaFQAscBcBAs5h3myYVDtGYstooiXzpqVeIB4kVus2LLAjrcieY rmTVnpOms3yewsFmqwnNSGQlTlvPiRRPgon8/uNrdU6ecf8bErhYWfmzo/VDNL91y1 mmE3niwtXR2kS0wlP5YmV1LiquITUyAkMuCGQprFBcxlXASwnBIQzy78QiyVSkC3xn E1uTWzoeDUF81anyAgjfMsoOTLa8Of82Jte969TF2IuQty8jNkGyAgF8HL3IYFMtKX Cp5v8B/Fb59Rg== From: Pratyush Yadav To: Mike Rapoport Cc: Pratyush Yadav , =?utf-8?B?TWljaGHFgiBDxYJhcGk=?= =?utf-8?B?xYRza2k=?= , Zi Yan , Evangelos Petrongonas , Pasha Tatashin , Alexander Graf , Samiullah Khawaja , kexec@lists.infradead.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Andrew Morton Subject: Re: [PATCH v7 2/3] kho: fix deferred init of kho scratch In-Reply-To: (Mike Rapoport's message of "Thu, 9 Apr 2026 21:06:08 +0300") References: <76559EF5-8740-4691-8776-0ADD1CCBF2A4@nvidia.com> <0D1F59C7-CA35-49C8-B341-32D8C7F4A345@nvidia.com> <58A8B1B4-A73B-48D2-8492-A58A03634644@nvidia.com> <2vxzwlyj9d0b.fsf@kernel.org> Date: Thu, 16 Apr 2026 09:41:14 +0000 Message-ID: <2vxzo6jj6y4l.fsf@kernel.org> User-Agent: Gnus/5.13 (Gnus v5.13) MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable X-Stat-Signature: z8jqm7y5z9h9zmngwmun8ey1xyyuimai X-Rspamd-Queue-Id: 7EF39140009 X-Rspam-User: X-Rspamd-Server: rspam06 X-HE-Tag: 1776332480-910874 X-HE-Meta: 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 4wqM3BEa 7UdK55Ei2WZj+oy8NJfm8iW9mC7B+u+s+7WWl+w2EeEmCadzsA5Q+3n4t/8Y0zBfXrOCiLu4YeMsX/a0wKE/7mHTHLhq3WJIVRqMhbDAHhmdUtezeWiSMD8as2cMYVNuwmKw7h+QA+WVhsuOCZYx+80nFVE/g/b1khsyYmIB9eTGn20B8uUVmzizUc7oTHVConp5jixKQuaoL/dEHPUJyiKTh/7D4biQk/35K Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Thu, Apr 09 2026, Mike Rapoport wrote: > On Tue, Apr 07, 2026 at 12:21:56PM +0000, Pratyush Yadav wrote: >> On Sun, Mar 22 2026, Mike Rapoport wrote: >>=20 >> > On Thu, Mar 19, 2026 at 07:17:48PM +0100, Micha=C5=82 C=C5=82api=C5=84= ski wrote: [...] >> Can we just get rid of this entirely? And just update >> memmap_init_zone_range() to also look for scratch and set the >> migratetype correctly from the get go? That's more consistent IMO. The >> two main places that initialize the struct page, >> memmap_init_zone_range() and deferred_init_memmap_chunk(), check for >> scratch and set the migratetype correctly. > > We could. E.g. let memmap_init() check the memblock flags and pass the > migratetype to memmap_init_zone_range(). > > I wanted to avoid as much KHO code in mm/ as possible, but if it is must > have in deferred_init_memmap_chunk() we could add some to memmap_init() as > well. KHO fundamentally alters mm init, so I think it would be hard to keep it to a neat corner unfortunately... We have been somewhat successful so far, but that has come at the cost of performance. Once we start trying to improve performance, I reckon more and more of it will spill into mm init. >=20=20 >> > @@ -2061,12 +2060,15 @@ deferred_init_memmap_chunk(unsigned long start= _pfn, unsigned long end_pfn, >> > spfn =3D max(spfn, start_pfn); >> > epfn =3D min(epfn, end_pfn); >> >=20=20 >> > + if (memblock_is_kho_scratch_memory(PFN_PHYS(spfn))) >> > + mt =3D MIGRATE_CMA; >>=20 >> Would it make sense for for_each_free_mem_range() to also return the >> flags for the region? Then you won't have to do another search. It adds >> yet another parameter to it so no strong opinion, but something to >> consider. > > I hesitated a lot about this. > Have you seen memblock::__next_mem_range() signature? ;-) Fair enough :-O > > I decided to start with something correct, but slowish and leave the churn > and speed for later. --=20 Regards, Pratyush Yadav