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b=sbq0zAF8ZoyJ4/uRqYKb/iFdUnRXolH8+oI/TIRRzMqSZSt9zA5kQE0jsUEmJTEXj mk8R3WEuV/HVLTPG6Pt+mb/jCfI5SJGy3dwwWR0pIiai1Hcby8nZsidkp0W6bhkLLR /wjfCZT4mAuO4NKy/bmvJGeNQqJUqTCWAa2ZsDpc= Date: Tue, 11 Nov 2025 15:50:42 -0800 From: Andrew Morton To: Steven Rostedt Cc: Balbir Singh , linux-mm@kvack.org, linux-trace-kernel@vger.kernel.org, linux-kernel@vger.kernel.org, Masami Hiramatsu , Mathieu Desnoyers , David Hildenbrand , Zi Yan , Joshua Hahn , Rakie Kim , Byungchul Park , Gregory Price , Ying Huang , Alistair Popple Subject: Re: [PATCH] mm/migrate_device: Add tracepoints for debugging Message-Id: <20251111155042.b07ecb045c978fe4c457b1d0@linux-foundation.org> In-Reply-To: <20251110161954.47d88433@gandalf.local.home> References: <20251016054619.3174997-1-balbirs@nvidia.com> <20251110161954.47d88433@gandalf.local.home> X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: A14B240007 X-Stat-Signature: h59gbzwbe5iy48qmdjjqtrrunwdstnn9 X-HE-Tag: 1762905044-443944 X-HE-Meta: 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 XwQOKR9g tqB9M5YziA83bUCGp8NcJTiWwyVK01YULL5maLtmmz5A93bLd9kRnpEhvOV39ribbT7rtPFdtOfpQ18AXAoWZWpxtwpIAwLq7Pxr4rlpXyBRvvsLE9kDqilC3C0sUrnuzzBWCfPDPHL/KbKiRpE5l/mrQkVTcurMTXsCzQAzS8wJlC9Jo9E9JJWnFldhMrDKBL5ZAKzbSJsDuuNMRNeZCN00OjudcZi2L9loLLnOv7hHot+nnsQS4u1RopnZ29DLpoT0YZ5CpVCUXiMrFtIYQS/yytdZU/kcmCzQPCJPGxb6UlIZyNtW5nBmQIlVMj1/eddUwknzmZADcqdJ17itoKZSP9CDtZXRJh0/iQ9tDao06U16jM5At5B7FDXA9DzH7G+WeIZ65HQNN83MK0cPIzCK3As7Eu6vVfy0G8f1JhVnwQf7o1twZF0iyThUkzCG2J2KT+P4U4kz1qA0= 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, 10 Nov 2025 16:19:54 -0500 Steven Rostedt wrote: > On Thu, 16 Oct 2025 16:46:19 +1100 > Balbir Singh wrote: > > > Add tracepoints for debugging device migration flow in migrate_device.c. > > This is helpful in debugging how long migration took (time can be > > tracked backwards from migrate_device_finalize to migrate_vma_setup). > > > > A combination of these events along with existing thp:*, exceptions:* > > and migrate:* is very useful for debugging issues related to > > migration. > > > > ... > > > hmm-tests-855 [002] 50.042800: set_migration_pmd: addr=7f2908a00000, pmd=dfffffffd39ffe00 > > hmm-tests-855 [002] 50.062345: remove_migration_pmd: addr=7f2908a00000, pmd=efffffe00403fe00 > > Each TRACE_EVENT() is equivalent to: > > DECLARE_EVENT_CLASS(event, ...) > DEFINE_EVENT(event, event, ...) > > Where a class is around 4-5K in size, and the DEFINE_EVENT is between > 500 and 1k in size. > > By using a single DECLARE_EVENT_CLASS() for multiple events, you can save > several thousands of bytes of memory. Thanks for the detailed review. I'll drop this version of the patch.