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[109.81.31.43]) by smtp.gmail.com with UTF8SMTPSA id a640c23a62f3a-b35446f758csm313713666b.53.2025.09.25.23.55.51 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 25 Sep 2025 23:55:51 -0700 (PDT) Date: Fri, 26 Sep 2025 08:55:50 +0200 From: Michal Hocko To: Mauricio Faria de Oliveira Cc: Andrew Morton , Vlastimil Babka , Oscar Salvador , Suren Baghdasaryan , Brendan Jackman , Johannes Weiner , Zi Yan , linux-mm@kvack.org, linux-kernel@vger.kernel.org, kernel-dev@igalia.com Subject: Re: [PATCH 0/3] mm/page_owner: add options 'print_handle' and 'print_stack' for 'show_stacks' Message-ID: References: <20250924174023.261125-1-mfo@igalia.com> <4c2a467113efd085530eb055e4a4e1fe@igalia.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4c2a467113efd085530eb055e4a4e1fe@igalia.com> X-Rspamd-Queue-Id: CA6EB40006 X-Stat-Signature: i4gmm3pt5hks88wei1foazg65ymzwd84 X-Rspam-User: X-Rspamd-Server: rspam09 X-HE-Tag: 1758869753-356841 X-HE-Meta: U2FsdGVkX1+UOUbKhYOLa1W/F3CbyIMJGoCe9RjZVmVq/rEdtMSJvHMGFf78jOY6+UZgt0Y6Op52wTyTKfNUswGLHbpviJE7PkHLr/R2WXmOlimzub992IKnkDhjltkJBpXp4OTYXXN4qiiClwGX4gaTFkiqsDOjrIB5zc02Jz0ksEpFQmm17DylZRtyYaK6SRxpReuItj1GFSlrab6TSsNG/Gdx+qACYagLb2Ry2xzxSUh0z5JOTnz4063G2A41K07RlexEDnPP/8Thap1MNiSjO2ojUDBa7AJ0JGTMPLVlXU4v25WwEU6Jvu8B7R6Ypx2DLw574fJa7x71PyqyROuItchr3S0S3bMT4cTCWJraKSgiFgBogQ042QZW8yP85cael1Zxwael3wQp8S/f9b8yjqCs6yZkFKeM68F7rOgWXoGyvJqgWMfIEi8BwZwltZZYNp3hFRD9EnuRjk/VfRg7D3NKQsdhK0+Oazmx205qUNErH78EPQsvHu0EPfWBi+kjHF9whOe4THz5nXcHXNSjAZVYGP7XB9xjW2A0JuUaw/O+w02xqf3mtD+x2QUUJcFokXPAoMolHYPSVcMeom4hbetPKN3YnS+1pRFq3qCTG7ycbek+VHKTTVewwcY6Nps2jd8JTTOQnNd8PR0mr3bieElWhKZZCxJ4vIdpppUV3jxgxr2HRN0MZ158hbPp3lP9BP6VtkalRwMk8+ckK+6GUqKaY3Z3AZVdqv2CYuQNFHj6rKSD8q8VcWCIyGVCgDOE+hK1USDB0x8ntyG+oaJCQWd6gBI0OCt8cCizWLLWrJEWdDQlTO76iUXH6XBljzmFIbFulytT+kzvRY5GLNXqufMujKhh4UwHIf1aQ+4a7PSbsB4SZokfnUmrYjvoZUy+5iQZHLcxHqxLthHnv5vRPhJ4jWOC6VETyAB6m3/GJItA25RlvuGjDDOp9dFge1tcmRVFjEjVefft3JW CyAvQ3KW tVWPeXrNAWx3DaEWzVyUcoSXtLh1G/7feUfLQVum2XT6G+ifaNfqnY8MBYFP2TKFAnIAzhPYkEqs0P6BcUEzD4EznHs/WQUlecDwuMXeq7DEhA07tjRwQkUz1I96rqVDD0EWRZBPhDELnqSG7mXpflYJRT8aNpPy8zMIGf+nIgQpQmVDT5b4Hc4RXCUA/mwTBqiCks2XgfaW9O6bIgifh9LLRufNuPlu7txzKPTGLhbmhsT5Lr3IpQOqoVeYJ05YZdE7BVxKURCTM0vE9ATG79UroLetHmTtkkAolFd8+ECK77obZeM8oqBCpz9cYAWaUNVFcnkxe7ewt+D8M0OWMfwkBPL5qYZM1TnG+wdZW3/oUlz4= 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 Thu 25-09-25 16:38:46, Mauricio Faria de Oliveira wrote: > On 2025-09-25 13:08, Michal Hocko wrote: [...] > > Could you elaborate some more on why the performance really matters here? > > Sure. > > One reason is optimizing data processing. > > Currently, the step to obtain the key of a strack trace (e.g., hashing) > incurs > a considerable work (done for all stack traces, on every sample) that > actually > is duplicated work (the same result for each stack trace, on every > sample). OK, that was not really clear to me but the above seems to suggest that by hashing you really mean hashing in the userspace when trying to create a key so that you can watch memory consumption trends per stack trace (hash in this case) without post processing. Stating that more explicitly in the changelog along with an example on how you are using this would be really helpful. When the interface was originally introduced the primary usecase was to examine biggest memory consumers - e.g. when memory counters do not add up to counters that track most common users (e.g. userspace memory, slab caches etc.). In those case you need to see those stack traces as those are giving you the most valuable information. I can see you are coming from a different direction and you want to collect data repeatedly and watch for trends rather than analyzing a particular situation. This seems like a useful usecase in itself. My main question is whether this should squashed into the existing file with a rather strange semantic of controling the file content depending on a different file content. Instead, would it make more sense to add two more files, one to display your requested key:value data and another to resolve key -> stack trace? -- Michal Hocko SUSE Labs