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charset=UTF-8 Content-Transfer-Encoding: 8bit X-Rspamd-Queue-Id: CC96D1A000C X-Stat-Signature: m96c35sb7jwqyhg1frhe6uxdnf6r9hqo X-Rspam-User: X-Rspamd-Server: rspam07 X-HE-Tag: 1754638648-892434 X-HE-Meta: U2FsdGVkX1+MG4wDuK8F7VHkylFRCL3nqem2QGX2AajMTMtT5iBKHg4A9mWBMkQ3p1dfy9noTTV4IW1Wh6GCdwB0Y/f/WjQ8OSeXhbinn8M9SB6ZzUvTNw0x0YwdtxqKvuZXCdNyKn8F6mIOueCiks/VL+dchMbFDoOQdglQlGyUo+XJWZVCft4OHdDRFUthglzSYZLNJ9OINmivoogvPj+aYFB1DehpqtIJogkKR0QP16zDTbY7uEXrbbs2n5W6+AQlGdhXjKhOtuGY46UVTHSRP+O2eX+aMdV4UcoESkp3erZfeyc4SwmVxQVOt0jH5Y7KuB1OjC7EzMe82iap9Ivm57/0LrJ7q/5iLP9HpjeQRi9nHlgQh2fTTCPSv5pNuufSs0KOUnQR0UPzck4gvnm+1qE9GY1zsVKn7puD7S3Kvk7+qd/kr1oApTi1kePv1XcAh1MH0p6UbBX/fCl5ktuw4JGe5jmaWRLwk4YTfAfQQsUzX/e9Zy3AVR8Lr+7I1sQSQAa4tG8x/TUXpwMFQ8z2hYDCtVNZfiyYMlg/WOKleiu2Wt4ik29qNOj96caJ2dpuEWwrxqTeq95ZAHvslqKBRp2a2fFiP9GGOhuVu2okNXKFWHy4SoGOgkfWPC9p5qmt8JWQpYO2fgLtQGPFHtCoi/5KuE32KNQDXqnNUDZtgpUYh+9W3a4viqiCqUQ2SJyCIzI8svidW0iNiOAZkqMVzBfFEaR91BjLg7T2tiGAOV/t0i1NDJ4x09IQOWxFMmOUanlZYIaBT2g/xqUfoiyLE8NuXqcy7n6UGSQu0nQaKPG4tqRJ3btx38SWDn0sBk55N0cKuBRQTIP6G6J3YQgHWyK8+9AaPb1h0umJjSj1XXoHxbZtT5nM6JSFrZM+9N15X1vvxsyHs1J09X+ph9SekuApIkKbnh7TmpjUNezroMJijxfHZOEkwOjKJGbXitVLQerbtAK6Fft6PVI L0x9y4YP G9vTKlaglPC+SygCCj1IQRU6fTYnvuL8raZ/mEjDu6hblB0Sp9eOxe+c2TQ8U8eNVQ4cxXsO642hn4taHNje8QDpY2QC9qUXZsOuruBZ5CZkoplQMjdVXuT7LqcH1BoswfExXJYZRewqC6LHg/YZ/FCGLDBLGXsp6e4uxPqI8c3Xte0ccG48X+1aOnjWQc6EBMR7ANumYWvqWEQovJOhSX++//0mQ+AAdEaIP4yttXCjeZxWAi+COFQ9pO48TDUaa+JgoHRiA6yymnKK6+I3uq+Ir2GQda6OnhFxY3WEfpQqDuBxfT7yN9KTEKNQnTPq3JBdOZf8NecJxH+npweW3TvPcJvCGfGVvq2q+DdvySHrMctZ+9bU/+eF5E0rmiBjk8K4MgJBqECJUEhXfC42LWA5GII22SZrNAHtW13toW3cAauSaoPP6VfnWGg== 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 8/7/25 17:49, Alexander Krabler wrote: > On Thu, 7 Aug 2025 14:21, Hugh Dickins wrote: >> But another idea has just this moment occurred to me: anon THP splitting >> is another user of migration entries. Is it possible that kcompactd is >> not actually the cause of Alexander's issue, but that his RT tasks have >> (bad news! shouldn't be allowed) got anon THPs in them? > > No, we don't have transparent hugepages enabled. > (From Kconfig, this seems not even possible together with PREEMPT_RT.) > > From ftrace events (first message in this thread), we know that kcompactd0 > finally wakes our realtime thread(s). > > Given the information I got from here, the comment on the code [1] > and an older commit message [2], I suspect CMA somehow influences our problem. However, kcompactd doesn't perform CMA allocations, only compaction, in a mode that does not include ISOLATE_UNEVICTABLE. So this is weird. > If there is anything we should enable for better diagnosis (e.g. more ftrace events), > we would be willing to try that out. > > [1] https://elixir.bootlin.com/linux/v6.16/source/mm/compaction.c#L1136 > [2] https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=e46a28790e594c0876d1a84270926abf75460f61 > > Thanks, > Alexander > > -- > KUKA Deutschland GmbH Board of Directors: Michael Jürgens (Chairman), Dirk Busch, Johan Naten, Hui Zhang Registered Office: Augsburg HRB 14914 > > This e-mail may contain confidential and/or privileged information. If you are not the intended recipient (or have received this e-mail in error) please notify the sender immediately and destroy this e-mail. Any unauthorized copying, disclosure or distribution of contents of this e-mail is strictly forbidden. > > Please consider the environment before printing this e-mail.