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t=1679844169; bh=jPU/1PkEjmLpuG/yzDwbE8MsDf1jHD5VOMCtE/4q5oc=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=l+6tQbymSzTr6IS5BMRpGd5XX4HuYNdB8yFSqDlx1qkM8+ajHIhyB11NSAoyEi3X1 zsMtVyf/RD87g3xLIEcjT8Rw8oK7sksjCyLOWb4bnSyaFgi/4yJhQSD/DUqgLfYedC z7l43Imtg49EboK8X4ff1pDkxeKlccKwPIlE0f1uiPBIBTY2inebpqTus/toO2LFbw zt3SCtxf6O4usZlE2+E+C10tZBZNr8BQbOVL79tf1hj0APyBIMRluLfWD+KK/efO9I /3KmVvu1IQ9gaPZ98NCq83j+HnBbxc0rk7/a30FRo2xO0UpstqtDjo/s5Cpmy/4Uiu ZnBhbIpEKrhFQ== Date: Sun, 26 Mar 2023 23:22:42 +0800 From: Masami Hiramatsu (Google) To: Steven Rostedt Cc: Beau Belgrave , Vlastimil Babka , "Masami Hiramatsu (Google)" , mathieu.desnoyers@efficios.com, dcook@linux.microsoft.com, alanau@linux.microsoft.com, brauner@kernel.org, akpm@linux-foundation.org, ebiederm@xmission.com, keescook@chromium.org, tglx@linutronix.de, linux-trace-devel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH v8 11/11] tracing/user_events: Limit global user_event count Message-Id: <20230326232242.adb5ad253b3810aaf9686d2f@kernel.org> In-Reply-To: <20230324130659.587ecfd2@gandalf.local.home> References: <20230221211143.574-1-beaub@linux.microsoft.com> <20230221211143.574-12-beaub@linux.microsoft.com> <20230324081824.b917c2944da217e5239e1223@kernel.org> <20230324164353.GA1790@kbox> <20230324130659.587ecfd2@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-Rspamd-Queue-Id: AF3E4160017 X-Rspamd-Server: rspam09 X-Rspam-User: X-Stat-Signature: 3qyuspap3ap85dinfiitqbskzdkqqcuo X-HE-Tag: 1679844170-831074 X-HE-Meta: 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 yGOCD/Zb 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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: On Fri, 24 Mar 2023 13:06:59 -0400 Steven Rostedt wrote: > On Fri, 24 Mar 2023 09:43:53 -0700 > Beau Belgrave wrote: > > > > It was actually merged in 5.8. So sysctl should be sufficient with that. > > > But maybe it's weird to start adding sysctls, when the rest of tracing > > > tunables is AFAIK under /sys/kernel/tracing/ ? > > > > > > > During the TraceFS meetings Steven runs I was asked to add a boot > > parameter and sysctl for user_events to limit the max. > > > > To me, it seems when user_events moves toward namespace awareness > > sysctl might be easier to use from within a namespace to turn knobs. > > > > Happy to change to whatever, but I want to see Steven and Masami agree > > on the approach before doing so. > > > > Steven, do you agree with Masami to move to just sysctl? > > We do have some tracing related sysctls already: > > # cd /proc/sys/kernel > # ls *trace* > ftrace_dump_on_oops oops_all_cpu_backtrace traceoff_on_warning > ftrace_enabled stack_tracer_enabled tracepoint_printk > > Although I would love to deprecated ftrace_enable as that now has a > control in tracefs, but it's not unprecedented to have tracing tunables as > sysctl. > > And if we get cmdline boot parameters for free from sysctls then all the > better. Yeah, I confirmed that sysctl can be set via kernel parameter. So it is OK for me to add a sysctl. Thank you, > > -- Steve -- Masami Hiramatsu (Google)