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Thu, 16 Apr 2026 08:10:36 -0700 (PDT) MIME-Version: 1.0 References: <20260416102558.575210-1-ekffu200098@gmail.com> In-Reply-To: From: Sang-Heon Jeon Date: Fri, 17 Apr 2026 00:10:25 +0900 X-Gm-Features: AQROBzCifctjF8HGZ-_gE9TlXJgyb--ZL50_wZrMHz6bkvqVOknwdJc-K7NK-ik Message-ID: Subject: Re: [RFC PATCH v2] mm/fake-numa: fix under-allocation detection in uniform split To: Mike Rapoport Cc: akpm@linux-foundation.org, djbw@kernel.org, mingo@kernel.org, linux-mm@kvack.org, Donghyeon Lee , Munhui Chae Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Queue-Id: 89416100012 X-Rspamd-Server: rspam07 X-Stat-Signature: cqx35ojk7aurww9c4jurc8zpxjn3a4ps X-Rspam-User: X-HE-Tag: 1776352237-836517 X-HE-Meta: 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 pfiyfN/c YbMu9kDh0wZLhCKUGu2ZrSXPuhXUCcoWAMxnJenmnqRw31RjFDCRlB3W0gFnNmx5MGhk9jG543f6gt+ffpesSvGk/3sYPdjXGybliGF4ybqZ6DPC2miOiufeUC2bDQPLhgepqotEPBPeixnJv0/UsHHA7jqeyz+waotwZUbjy5d4WK2hJ+hLvee17RXLczdnq/qWuLERC1DVJza8q5RPYaSLiaChsNxs1jYJBmp45BXVau0S8oZ0+b4QUmvpC0JkGsb/lPwWX3Np3Y+s4/V8FL7hTTKW+6vl6qyIg6QlGVynLRUIuEl9vA+gWZAUDIdekTvhG+v4ijNfwnuwxelDaNrrhwGlNl3HFcYvY0HPHxkkBqxQmAidZst9Uom6XJXwo4iew7QYt2+EYh1wr44Vm45Pjk44f2u69dgiRA2e8PQstoITM8kQk/9Gm0NH1CyasxMlv Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Hello, On Thu, Apr 16, 2026 at 11:29=E2=80=AFPM Mike Rapoport wr= ote: > > Hi, > > On Thu, Apr 16, 2026 at 07:25:58PM +0900, Sang-Heon Jeon wrote: > > Subject: [RFC PATCH v2] mm/fake-numa: fix under-allocation detection in= uniform split > > RFC in the subject means you don't intent for the patch to be included, b= ut > rather want to share it to get an early feedback. > > I believe this is not the case here :) You're right. When I sent v1 patch, I wanted to check if the way of patch was correct or not. Anyway, it seems there are no disagreements on that part now. I'll remove RFC in the next patch. I really appreciate your attention :) > > When split NUMA node uniformly, split_nodes_size_interleave_uniform() > > returns the next absolute node ID, not the number of nodes created. > > > > The existing under-allocation detection logic compares next absolute no= de > > ID (ret) and request count (n), which only works when nid starts at 0. > > > > For example, on a system with 2 physical NUMA nodes (node 0: 2GB, node > > 1: 128MB) and numa=3Dfake=3D8U, 8 fake nodes are successfully created f= rom > > node 0 and split_nodes_size_interleave_uniform() returns 8. For node 1, > > fake node nid starts at 8, but only 4 fake nodes are created due to > > current FAKE_NODE_MIN_SIZE being 32MB, and > > split_nodes_size_interleave_uniform() returns 12. By existing > > under-allocation detection logic, "ret < n" (12 < 8) is false, so the > > under-allocation will not be detected. > > > > Fix under-allocation detection logic to compare the number of actually > > created nodes (ret - nid) against the request count (n). > > > > Also, fix the outdated comment to match the actual return value. > > > > Signed-off-by: Sang-Heon Jeon > > Reported-by: Donghyeon Lee > > Reported-by: Munhui Chae > > Fixes: cc9aec03e58f ("x86/numa_emulation: Introduce uniform split capab= ility") # 4.19 > > --- > > mm/numa_emulation.c | 4 ++-- > > 1 file changed, 2 insertions(+), 2 deletions(-) > > > > diff --git a/mm/numa_emulation.c b/mm/numa_emulation.c > > index 703c8fa05048..c1d0a76aef64 100644 > > --- a/mm/numa_emulation.c > > +++ b/mm/numa_emulation.c > > @@ -214,7 +214,7 @@ static u64 uniform_size(u64 max_addr, u64 base, u64= hole, int nr_nodes) > > * Sets up fake nodes of `size' interleaved over physical nodes rangin= g from > > * `addr' to `max_addr'. > > * > > - * Returns zero on success or negative on error. > > + * Returns absolute node ID on success or negative on error. > > */ > > static int __init split_nodes_size_interleave_uniform(struct numa_memi= nfo *ei, > > struct numa_meminfo *pi, > > @@ -416,7 +416,7 @@ void __init numa_emulation(struct numa_meminfo *num= a_meminfo, int numa_dist_cnt) > > n, &pi.blk[0], nid); > > if (ret < 0) > > break; > > - if (ret < n) { > > + if (ret - nid < n) { > > pr_info("%s: phys: %d only got %d of %ld = nodes, failing\n", > > __func__, i, ret, n); > > ret =3D -1; > > -- > > 2.43.0 > > > > -- > Sincerely yours, > Mike. Best Regards, Sang-Heon Jeon