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cv=none; b=jHo6xdZylgxKTqjHdwyNq3barjFtxuoB2N3fT4kAliOr3+scNyWIfrm9xH3Bhsn/XIr9sC mntPVLQoeAg+jxYGM6Q/SoVzKTqESY4XThTbJHCOdZM54sRFX595P2MsU5/yBLQiLwPnTx +AU8j5DXvdfB+YubfU0BvQhDtDdFB+0= Received: from omf08.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay10.hostedemail.com (Postfix) with ESMTP id 0F89CC07CE; Mon, 15 Sep 2025 23:41:03 +0000 (UTC) Received: from [HIDDEN] (Authenticated sender: rostedt@goodmis.org) by omf08.hostedemail.com (Postfix) with ESMTPA id E2C4D20026; Mon, 15 Sep 2025 23:40:55 +0000 (UTC) Date: Mon, 15 Sep 2025 19:41:58 -0400 From: Steven Rostedt To: Kalesh Singh Cc: akpm@linux-foundation.org, minchan@kernel.org, lorenzo.stoakes@oracle.com, david@redhat.com, Liam.Howlett@oracle.com, rppt@kernel.org, pfalcato@suse.de, kernel-team@android.com, android-mm@google.com, Alexander Viro , Christian Brauner , Jan Kara , Kees Cook , Vlastimil Babka , Suren Baghdasaryan , Michal Hocko , Masami Hiramatsu , Mathieu Desnoyers , Ingo Molnar , Peter Zijlstra , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Ben Segall , Mel Gorman , Valentin Schneider , Jann Horn , Shuah Khan , linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-trace-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org Subject: Re: [PATCH v2 7/7] mm/tracing: introduce max_vma_count_exceeded trace event Message-ID: <20250915194158.472edea5@gandalf.local.home> In-Reply-To: <20250915163838.631445-8-kaleshsingh@google.com> References: <20250915163838.631445-1-kaleshsingh@google.com> <20250915163838.631445-8-kaleshsingh@google.com> X-Mailer: Claws Mail 3.20.0git84 (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-Session-Marker: 726F737465647440676F6F646D69732E6F7267 X-Session-ID: U2FsdGVkX182V87XcZg9olTniRrbK41HEticcPkYuYw= X-HE-Meta: U2FsdGVkX19Zx1if+NNOzNVMgDMyEiQRf5KCrWoxEDdLlNyy025itEj2zjYJBMkNwUQkqjVFWdtFRA5Ynf4Yz52t7Y1DGnQ2OrwsGDN+DfgeyZ/AjYltT/l+Fuc8hpc2wOnrMa4yD4BId/vidyDiRLVZf5kH/cEGKQMrhL9USmC5wPTmd/XZBCPSslcwAPZSJYKJrh1jOkhQdQrzGMZhwDuGvOx64jO6Sdz5jN+n3mxHtNycmWq2UKphdEubae/8110tkn8jyhlLd+mre6+YjdQCeFduvdoPDJUesJYNt8Y1VSJVf19uZJ2Wze55wXrfVIdxUSD+IxDLITtQ30dzIQMUtN1rlpTd X-HE-Tag-Orig: 1757979655-928162 X-Rspamd-Queue-Id: CAC3240002 X-Rspamd-Server: rspam05 X-Stat-Signature: df3ccaam1mxrnods7yhuxspu6mdbkrdh X-Rspam-User: X-HE-Tag: 1757979666-687890 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 Mon, 15 Sep 2025 09:36:38 -0700 Kalesh Singh wrote: > Needed observability on in field devices can be collected with minimal > overhead and can be toggled on and off. Event driven telemetry can be > done with tracepoint BPF programs. > > The process comm is provided for aggregation across devices and tgid is > to enable per-process aggregation per device. What do you mean about comm being used to aggregation across devices? What's special about this trace event that will make it used across devices? Note, if BPF is being used, can't the BPF program just add the current comm? Why waste space in the ring buffer for it? > + > +TRACE_EVENT(max_vma_count_exceeded, > + > + TP_PROTO(struct task_struct *task), Why pass in the task if it's always going to be current? > + > + TP_ARGS(task), > + > + TP_STRUCT__entry( > + __string(comm, task->comm) This could be: __string(comm, current) But I still want to know what makes this trace event special over other trace events to store this, and can't it be retrieved another way, especially if BPF is being used to hook to it? -- Steve > + __field(pid_t, tgid) > + ), > + > + TP_fast_assign( > + __assign_str(comm); > + __entry->tgid = task->tgid; > + ), > + > + TP_printk("comm=%s tgid=%d", __get_str(comm), __entry->tgid) > +); > +