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From: Kent Overstreet To: Suren Baghdasaryan Cc: 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, david@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 31/35] lib: add memory allocations report in show_mem() Message-ID: References: <20240212213922.783301-1-surenb@google.com> <20240212213922.783301-32-surenb@google.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-Rspamd-Queue-Id: CCF4940014 X-Rspam-User: X-Stat-Signature: oz49rdjiu8h1oaycj7g9uchdxik6y99p X-Rspamd-Server: rspam03 X-HE-Tag: 1708022299-198065 X-HE-Meta: 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 JOOn1e93 yoBRA/deRi10pqpoiwLCBIZgnOs2X4Uz2fIl+0skwk7IpGe8w96SUXOXXbQFmzlbPFKJzS1NxNSxfhpIh1MW7J9ECr+fD9zNm/8qyYCKRiq1LnyG9hyJrOA6//opCogvCAT+yMnI/dMysw5NtM9jMR+y4e+vm90zlX8UJz84laYhxpr9yKtcVoeCwBaO5yjciuV3mpLkPg1xYz78g5ojX3cX777emDs6hRLMxgonDmURDBTIX35M17t1L9dfpUzHbB3Gw 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, Feb 15, 2024 at 10:33:53AM -0800, Suren Baghdasaryan wrote: > On Thu, Feb 15, 2024 at 10:29 AM Kent Overstreet > wrote: > > > > On Thu, Feb 15, 2024 at 08:47:59AM -0800, Suren Baghdasaryan wrote: > > > On Thu, Feb 15, 2024 at 8:45 AM Michal Hocko wrote: > > > > > > > > On Thu 15-02-24 06:58:42, Suren Baghdasaryan wrote: > > > > > On Thu, Feb 15, 2024 at 1:22 AM Michal Hocko wrote: > > > > > > > > > > > > On Mon 12-02-24 13:39:17, Suren Baghdasaryan wrote: > > > > > > [...] > > > > > > > @@ -423,4 +424,18 @@ void __show_mem(unsigned int filter, nodemask_t *nodemask, int max_zone_idx) > > > > > > > #ifdef CONFIG_MEMORY_FAILURE > > > > > > > printk("%lu pages hwpoisoned\n", atomic_long_read(&num_poisoned_pages)); > > > > > > > #endif > > > > > > > +#ifdef CONFIG_MEM_ALLOC_PROFILING > > > > > > > + { > > > > > > > + struct seq_buf s; > > > > > > > + char *buf = kmalloc(4096, GFP_ATOMIC); > > > > > > > + > > > > > > > + if (buf) { > > > > > > > + printk("Memory allocations:\n"); > > > > > > > + seq_buf_init(&s, buf, 4096); > > > > > > > + alloc_tags_show_mem_report(&s); > > > > > > > + printk("%s", buf); > > > > > > > + kfree(buf); > > > > > > > + } > > > > > > > + } > > > > > > > +#endif > > > > > > > > > > > > I am pretty sure I have already objected to this. Memory allocations in > > > > > > the oom path are simply no go unless there is absolutely no other way > > > > > > around that. In this case the buffer could be preallocated. > > > > > > > > > > Good point. We will change this to a smaller buffer allocated on the > > > > > stack and will print records one-by-one. Thanks! > > > > > > > > __show_mem could be called with a very deep call chains. A single > > > > pre-allocated buffer should just do ok. > > > > > > Ack. Will do. > > > > No, we're not going to permanently burn 4k here. > > We don't need 4K here. Just enough to store one line and then print > these 10 highest allocations one line at a time. This way we can also > change that 10 to any higher number we like without any side effects. There's no reason to make the change at all. If Michal thinks there's something "dangerous" about allocating a buffer here, he needs to able to explain what it is.