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Fri, 30 Jul 2021 08:12:38 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap1.suse-dmz.suse.de with ESMTPSA id XbdrNHa0A2FODQAAGKfGzw (envelope-from ); Fri, 30 Jul 2021 08:12:38 +0000 Subject: Re: [PATCH 3/3] mm: mmap_lock: add ip to mmap_lock tracepoints To: Axel Rasmussen , Gang Li Cc: Steven Rostedt , Ingo Molnar , Andrew Morton , LKML , Linux MM References: <20210729092853.38242-1-ligang.bdlg@bytedance.com> From: Vlastimil Babka Message-ID: <34dcbcac-7794-c067-3d71-7a1404c41b6c@suse.cz> Date: Fri, 30 Jul 2021 10:12:38 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.12.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: 8EBFF5003D6E Authentication-Results: imf04.hostedemail.com; dkim=pass header.d=suse.cz header.s=susede2_rsa header.b=slCzJsYd; dkim=pass header.d=suse.cz header.s=susede2_ed25519 header.b=+LpZlHaP; spf=pass (imf04.hostedemail.com: domain of vbabka@suse.cz designates 195.135.220.29 as permitted sender) smtp.mailfrom=vbabka@suse.cz; dmarc=none X-Stat-Signature: a6y38k5tdpqxr7jy8ur5b1rg3ysgoyiy X-HE-Tag: 1627632760-144122 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 7/29/21 7:33 PM, Axel Rasmussen wrote: > Not a strong objection, but I think this can be achieved already using either: > > - The "stacktrace" feature which histogram triggers support > (https://www.kernel.org/doc/html/latest/trace/histogram.html) > - bpftrace's kstack/ustack feature > (https://github.com/iovisor/bpftrace/blob/master/docs/tutorial_one_liners.md#lesson-9-profile-on-cpu-kernel-stacks) > > I haven't tried it out myself, but I suspect you could construct a > synthetic event > (https://www.kernel.org/doc/html/latest/trace/histogram.html#synthetic-events) > which adds in the stack trace, then it ought to function a lot like it > would with this patch. > > Then again, it's not like this change is huge by any means. So, if you > find this more convenient than those alternatives, you can take: > > Reviewed-by: Axel Rasmussen > > It's possible Steven or Tom have a more strong opinion on this though. ;) I generally dislike tracepoints with an ip. Often you then find out it's not enough to distinguish what you need (due to some commonly shared wrapper doing the call) and you need more of the backtrace anyway.