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From: Kent Overstreet To: David Hildenbrand Cc: Suren Baghdasaryan , Michal Hocko , akpm@linux-foundation.org, vbabka@suse.cz, hannes@cmpxchg.org, roman.gushchin@linux.dev, mgorman@suse.de, dave@stgolabs.net, willy@infradead.org, liam.howlett@oracle.com, corbet@lwn.net, void@manifault.com, peterz@infradead.org, juri.lelli@redhat.com, catalin.marinas@arm.com, will@kernel.org, arnd@arndb.de, tglx@linutronix.de, mingo@redhat.com, dave.hansen@linux.intel.com, x86@kernel.org, peterx@redhat.com, axboe@kernel.dk, mcgrof@kernel.org, masahiroy@kernel.org, nathan@kernel.org, dennis@kernel.org, tj@kernel.org, muchun.song@linux.dev, rppt@kernel.org, paulmck@kernel.org, pasha.tatashin@soleen.com, yosryahmed@google.com, yuzhao@google.com, dhowells@redhat.com, hughd@google.com, andreyknvl@gmail.com, keescook@chromium.org, ndesaulniers@google.com, vvvvvv@google.com, gregkh@linuxfoundation.org, ebiggers@google.com, ytcoode@gmail.com, vincent.guittot@linaro.org, dietmar.eggemann@arm.com, rostedt@goodmis.org, bsegall@google.com, bristot@redhat.com, vschneid@redhat.com, cl@linux.com, penberg@kernel.org, iamjoonsoo.kim@lge.com, 42.hyeyoo@gmail.com, glider@google.com, elver@google.com, dvyukov@google.com, shakeelb@google.com, songmuchun@bytedance.com, jbaron@akamai.com, rientjes@google.com, minchan@google.com, kaleshsingh@google.com, kernel-team@android.com, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, iommu@lists.linux.dev, linux-arch@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-modules@vger.kernel.org, kasan-dev@googlegroups.com, cgroups@vger.kernel.org Subject: Re: [PATCH v3 00/35] Memory allocation profiling Message-ID: References: <9e14adec-2842-458d-8a58-af6a2d18d823@redhat.com> <2hphuyx2dnqsj3hnzyifp5yqn2hpgfjuhfu635dzgofr5mst27@4a5dixtcuxyi> <6a0f5d8b-9c67-43f6-b25e-2240171265be@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-Migadu-Flow: FLOW_OUT X-Rspam-User: X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 7C7E640009 X-Stat-Signature: 4xgao3aenhun63guk3dgti3onkc8zsn4 X-HE-Tag: 1707865971-979290 X-HE-Meta: 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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 Wed, Feb 14, 2024 at 12:02:30AM +0100, David Hildenbrand wrote: > On 13.02.24 23:59, Suren Baghdasaryan wrote: > > On Tue, Feb 13, 2024 at 2:50 PM Kent Overstreet > > wrote: > > > > > > On Tue, Feb 13, 2024 at 11:48:41PM +0100, David Hildenbrand wrote: > > > > On 13.02.24 23:30, Suren Baghdasaryan wrote: > > > > > On Tue, Feb 13, 2024 at 2:17 PM David Hildenbrand wrote: > > > > > > > > > > > > On 13.02.24 23:09, Kent Overstreet wrote: > > > > > > > On Tue, Feb 13, 2024 at 11:04:58PM +0100, David Hildenbrand wrote: > > > > > > > > On 13.02.24 22:58, Suren Baghdasaryan wrote: > > > > > > > > > On Tue, Feb 13, 2024 at 4:24 AM Michal Hocko wrote: > > > > > > > > > > > > > > > > > > > > On Mon 12-02-24 13:38:46, Suren Baghdasaryan wrote: > > > > > > > > > > [...] > > > > > > > > > > > We're aiming to get this in the next merge window, for 6.9. The feedback > > > > > > > > > > > we've gotten has been that even out of tree this patchset has already > > > > > > > > > > > been useful, and there's a significant amount of other work gated on the > > > > > > > > > > > code tagging functionality included in this patchset [2]. > > > > > > > > > > > > > > > > > > > > I suspect it will not come as a surprise that I really dislike the > > > > > > > > > > implementation proposed here. I will not repeat my arguments, I have > > > > > > > > > > done so on several occasions already. > > > > > > > > > > > > > > > > > > > > Anyway, I didn't go as far as to nak it even though I _strongly_ believe > > > > > > > > > > this debugging feature will add a maintenance overhead for a very long > > > > > > > > > > time. I can live with all the downsides of the proposed implementation > > > > > > > > > > _as long as_ there is a wider agreement from the MM community as this is > > > > > > > > > > where the maintenance cost will be payed. So far I have not seen (m)any > > > > > > > > > > acks by MM developers so aiming into the next merge window is more than > > > > > > > > > > little rushed. > > > > > > > > > > > > > > > > > > We tried other previously proposed approaches and all have their > > > > > > > > > downsides without making maintenance much easier. Your position is > > > > > > > > > understandable and I think it's fair. Let's see if others see more > > > > > > > > > benefit than cost here. > > > > > > > > > > > > > > > > Would it make sense to discuss that at LSF/MM once again, especially > > > > > > > > covering why proposed alternatives did not work out? LSF/MM is not "too far" > > > > > > > > away (May). > > > > > > > > > > > > > > > > I recall that the last LSF/MM session on this topic was a bit unfortunate > > > > > > > > (IMHO not as productive as it could have been). Maybe we can finally reach a > > > > > > > > consensus on this. > > > > > > > > > > > > > > I'd rather not delay for more bikeshedding. Before agreeing to LSF I'd > > > > > > > need to see a serious proposl - what we had at the last LSF was people > > > > > > > jumping in with half baked alternative proposals that very much hadn't > > > > > > > been thought through, and I see no need to repeat that. > > > > > > > > > > > > > > Like I mentioned, there's other work gated on this patchset; if people > > > > > > > want to hold this up for more discussion they better be putting forth > > > > > > > something to discuss. > > > > > > > > > > > > I'm thinking of ways on how to achieve Michal's request: "as long as > > > > > > there is a wider agreement from the MM community". If we can achieve > > > > > > that without LSF, great! (a bi-weekly MM meeting might also be an option) > > > > > > > > > > There will be a maintenance burden even with the cleanest proposed > > > > > approach. > > > > > > > > Yes. > > > > > > > > > We worked hard to make the patchset as clean as possible and > > > > > if benefits still don't outweigh the maintenance cost then we should > > > > > probably stop trying. > > > > > > > > Indeed. > > > > > > > > > At LSF/MM I would rather discuss functonal > > > > > issues/requirements/improvements than alternative approaches to > > > > > instrument allocators. > > > > > I'm happy to arrange a separate meeting with MM folks if that would > > > > > help to progress on the cost/benefit decision. > > > > Note that I am only proposing ways forward. > > > > > > > > If you think you can easily achieve what Michal requested without all that, > > > > good. > > > > > > He requested something? > > > > Yes, a cleaner instrumentation. Unfortunately the cleanest one is not > > possible until the compiler feature is developed and deployed. And it > > still would require changes to the headers, so don't think it's worth > > delaying the feature for years. > > > > I was talking about this: "I can live with all the downsides of the proposed > implementationas long as there is a wider agreement from the MM community as > this is where the maintenance cost will be payed. So far I have not seen > (m)any acks by MM developers". > > I certainly cannot be motivated at this point to review and ack this, > unfortunately too much negative energy around here. David, this kind of reaction is exactly why I was telling Andrew I was going to submit this as a direct pull request to Linus. This is an important feature; if we can't stay focused ot the technical and get it done that's what I'll do.