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a=rsa-sha256; c=relaxed/relaxed; d=stgolabs.net; s=dreamhost; t=1708370779; bh=Hn2l3d45OvLwYGiCr0LlqsBI++buxfvs3HMYLYE8Fk4=; h=Date:From:To:Cc:Subject:Content-Type; b=WBOZqsAYKS9HgVsjtYxiIK9i0CM1ATn7RXh9NGZcdf2nD6iyhaa4bVyH3H8dHdBxR wuGXtz+1CKgaK+WP118KJPyiempcvgvCkNcsybhkErAu/4cgASzeuHe7lDiISwdBqu JKPqhyCRoEfFjOFRuuxO9L4benP/dih3t0ERyPBjq4uQ/2WvFcFNuwYa2bIq9p1oTk kcR9paTrIQN5kfnOy/D5FC/9/vEmcUhIy8sdjG3FjUz7XL+H/VoD7yqrCeMs1TnqqU vrjpym5dV5T1zt0lwXn2te1jDwHA5zZbTagcezJr5eZci/fXz5xUFDWlgJg03b8lc4 qejgiwv7aw8fA== Date: Mon, 19 Feb 2024 11:26:15 -0800 From: Davidlohr Bueso To: Oscar Salvador Cc: Byungchul Park , mingo@redhat.com, peterz@infradead.org, juri.lelli@redhat.com, vincent.guittot@linaro.org, dietmar.eggemann@arm.com, rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de, bristot@redhat.com, vschneid@redhat.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, kernel_team@skhynix.com, akpm@linux-foundation.org, fan.ni@samsung.com Subject: Re: [PATCH v3] sched/numa, mm: do not promote folios to nodes not set N_MEMORY Message-ID: <20240219192615.adgr4cfknnb356de@offworld> Mail-Followup-To: Oscar Salvador , Byungchul Park , mingo@redhat.com, peterz@infradead.org, juri.lelli@redhat.com, vincent.guittot@linaro.org, dietmar.eggemann@arm.com, rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de, bristot@redhat.com, vschneid@redhat.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, kernel_team@skhynix.com, akpm@linux-foundation.org, fan.ni@samsung.com References: <20240216114045.24828-1-byungchul@sk.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Disposition: inline In-Reply-To: User-Agent: NeoMutt/20220429 X-Rspamd-Queue-Id: 80C6F140021 X-Rspam-User: X-Rspamd-Server: rspam02 X-Stat-Signature: gfw4484bh8shx75pu5f65oze8uuoiw6w X-HE-Tag: 1708370782-18497 X-HE-Meta: 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 PNJFZPLe 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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 Sun, 18 Feb 2024, Oscar Salvador wrote: >On Fri, Feb 16, 2024 at 02:51:24PM +0100, Oscar Salvador wrote: >> On Fri, Feb 16, 2024 at 08:40:45PM +0900, Byungchul Park wrote: >> > From 150af2f78e19217a1d03e47e3ee5279684590fb4 Mon Sep 17 00:00:00 2001 >> > From: Byungchul Park >> > Date: Fri, 16 Feb 2024 20:18:10 +0900 >> > Subject: [PATCH v3] sched/numa, mm: do not promote folios to nodes not set N_MEMORY >> >> "do not try to promote folios to memoryless nodes" > >Thinking some more, promote might be misleading, just something like >"do not try to migrate memory to memoryless nodes". Yes. Does this also want an unlikely()? Not that it would be measurable. >As this is not a bug fix but an optimization, as we will fail anyways >in migrate_misplaced_folio() when migrate_balanced_pgdat() notices that >we do not have any memory on that code. This should be in the changelog and the subject is misleading as well. Reviewed-by: Davidlohr Bueso > >With the other comments addressed: > >Reviewed-by: Oscar Salvador > >> >> because AFAICS we are just trying. >> Even if should_numa_migrate_memory() returns true, I assume that we will >> fail somewhere down the chain e.g: migrate_pages() when we see that this >> node does not any memory, right? >> >> > A numa node might not have its local memory but CPUs. Promoting a folio >> > to the node's local memory is nonsense. So avoid nodes not set N_MEMORY >> > from getting promoted. >> >> If you talk about memoryless nodes everybody gets it better IMHO. >> "Memoryless nodes do not have any memory to migrate to, so stop trying it." >> >> >> > Signed-off-by: Byungchul Park >> > --- >> > kernel/sched/fair.c | 7 +++++++ >> > 1 file changed, 7 insertions(+) >> > >> > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c >> > index d7a3c63a2171..7ed9ef3c0134 100644 >> > --- a/kernel/sched/fair.c >> > +++ b/kernel/sched/fair.c >> > @@ -1828,6 +1828,13 @@ bool should_numa_migrate_memory(struct task_struct *p, struct folio *folio, >> > int dst_nid = cpu_to_node(dst_cpu); >> > int last_cpupid, this_cpupid; >> > >> > + /* >> > + * A node of dst_nid might not have its local memory. Promoting >> > + * a folio to the node is meaningless. >> > + */ >> > + if (!node_state(dst_nid, N_MEMORY)) >> > + return false; >> >> "Cannot migrate to memoryless nodes" >> >> seems shorter and more clear. >> >> So, what happens when we return true here? will we fail at >> migrate_pages() I guess? That is quite down the road so I guess >> this check can save us some time. >> >> >> -- >> Oscar Salvador >> SUSE Labs >> > >-- >Oscar Salvador >SUSE Labs >