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b=Kry9SWYtgvdutxvXmjz7kw2FjM D4Mh+YtXTIKEFOeFDFrG/Bs5kNB2DI0eCiJBF9ohZNNXeq4rT2h4WQ0Mj5VddscfGpMjkhpwEzPP1 k9Jk65lptDjMFQ1n5wKbUMNl1cixjK1hCGT6sKxuL8UM5OU/jEohuJWv9W9ps8HAFECu5rVSE9aH3 GALfPULwTqOmjtJc4lj7X1HCOeVELOJdXDob2cfiPWUFqNI7Ats4xtjXF4GBCoRkFydXdbkBZJIj/ AcIpXLmHIVtcxTGBJ2bxNRsE5RWsJ/lfck6GQAtXFo5td7mpCKI9ouhrnjaeETlwY/KZkNaKQ6hNB vWMBRKoA==; Received: from fangorn.home.surriel.com ([10.0.13.7]) by shelob.surriel.com with esmtpsa (TLS1.2) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.97.1) (envelope-from ) id 1uyis8-000000003qc-1Q3q; Tue, 16 Sep 2025 23:30:20 -0400 Message-ID: <190cd3842bc0776611c73a439e49ba57c86849d1.camel@surriel.com> Subject: Re: [RFC PATCH 06/12] mm/cma: define and act on CMA_BALANCE flag From: Rik van Riel To: Frank van der Linden , akpm@linux-foundation.org, muchun.song@linux.dev, linux-mm@kvack.org, linux-kernel@vger.kernel.org Cc: hannes@cmpxchg.org, david@redhat.com, roman.gushchin@linux.dev Date: Tue, 16 Sep 2025 23:30:20 -0400 In-Reply-To: <20250915195153.462039-7-fvdl@google.com> References: <20250915195153.462039-1-fvdl@google.com> <20250915195153.462039-7-fvdl@google.com> Autocrypt: addr=riel@surriel.com; 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charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.54.3 (3.54.3-1.fc41) MIME-Version: 1.0 X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: CD02FC0004 X-Stat-Signature: xbh9qdj6r3xa5rrqngwdu7i6sf5usaoh X-Rspam-User: X-HE-Tag: 1758079841-581087 X-HE-Meta: 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Mon, 2025-09-15 at 19:51 +0000, Frank van der Linden wrote: >=20 > @@ -851,7 +862,10 @@ int __init > cma_declare_contiguous_multi(phys_addr_t total_size, > =C2=A0 list_for_each_safe(mp, next, &ranges) { > =C2=A0 mlp =3D list_entry(mp, struct cma_init_memrange, > list); > =C2=A0 list_del(mp); > - list_insert_sorted(&final_ranges, mlp, basecmp); > + if (flags & CMA_BALANCE) > + list_insert_sorted(&final_ranges, mlp, > revbasecmp); > + else > + list_insert_sorted(&final_ranges, mlp, > basecmp); > =C2=A0 sizesum +=3D mlp->size; > =C2=A0 if (sizesum >=3D total_size) > =C2=A0 break; Wait, what is this supposed to do when presented with a mix of CMA_BALANCE and !CMA_BALANCE ranges? I can't convince myself this would always keep the CMA_BALANCE range near the top of the list, and the others near the bottom. Also, does the regular compaction code pay any attention to the order of this list? I have the feeling I am overlooking something big in how this patch is supposed to work, but I am not sure what that would be... > @@ -866,7 +880,12 @@ int __init > cma_declare_contiguous_multi(phys_addr_t total_size, > =C2=A0 list_for_each(mp, &final_ranges) { > =C2=A0 mlp =3D list_entry(mp, struct cma_init_memrange, > list); > =C2=A0 size =3D min(sizeleft, mlp->size); > - if (memblock_reserve(mlp->base, size)) { > + if (flags & CMA_BALANCE) > + start =3D (mlp->base + mlp->size - size); > + else > + start =3D mlp->base; > + > + if (memblock_reserve(start, size)) { > =C2=A0 /* > =C2=A0 * Unexpected error. Could go on to > =C2=A0 * the next one, but just abort to >=20 --=20 All Rights Reversed.