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Mon, 02 Dec 2019 15:45:16 -0800 (PST) Received: from localhost ([2620:15c:6:12:9c46:e0da:efbf:69cc]) by smtp.gmail.com with ESMTPSA id j20sm592992pff.182.2019.12.02.15.45.14 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 02 Dec 2019 15:45:15 -0800 (PST) Date: Mon, 2 Dec 2019 18:45:14 -0500 From: Joel Fernandes To: Steven Rostedt Cc: akpm@linux-foundation.org, aneesh.kumar@linux.ibm.com, carmenjackson@google.com, dan.j.williams@intel.com, dancol@google.com, jglisse@redhat.com, linux-mm@kvack.org, mayankgupta@google.com, mhocko@suse.com, minchan@kernel.org, mm-commits@vger.kernel.org, rcampbell@nvidia.com, timmurray@google.com, torvalds@linux-foundation.org, vbabka@suse.cz, willy@infradead.org, primiano@google.com Subject: Re: [patch 026/158] mm: emit tracepoint when RSS changes Message-ID: <20191202234514.GR17234@google.com> References: <20191201015030.MR-ux4mV1%akpm@linux-foundation.org> <20191202121415.1e64a461@gandalf.local.home> <20191202211345.GE17234@google.com> <20191202165601.42366c21@gandalf.local.home> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20191202165601.42366c21@gandalf.local.home> User-Agent: Mutt/1.10.1 (2018-07-13) 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 Mon, Dec 02, 2019 at 04:56:01PM -0500, Steven Rostedt wrote: > On Mon, 2 Dec 2019 16:13:45 -0500 > Joel Fernandes wrote: > > > On Mon, Dec 02, 2019 at 12:14:15PM -0500, Steven Rostedt wrote: > > > On Sat, 30 Nov 2019 17:50:30 -0800 > > > akpm@linux-foundation.org wrote: > > > > > > > /* Optimized variant when page is already known not to be PageAnon */ > > > > --- a/include/trace/events/kmem.h~mm-emit-tracepoint-when-rss-changes > > > > +++ a/include/trace/events/kmem.h > > > > @@ -316,6 +316,27 @@ TRACE_EVENT(mm_page_alloc_extfrag, > > > > __entry->change_ownership) > > > > ); > > > > > > > > +TRACE_EVENT(rss_stat, > > > > + > > > > + TP_PROTO(int member, > > > > + long count), > > > > + > > > > + TP_ARGS(member, count), > > > > + > > > > + TP_STRUCT__entry( > > > > + __field(int, member) > > > > + __field(long, size) > > > > + ), > > > > + > > > > + TP_fast_assign( > > > > + __entry->member = member; > > > > + __entry->size = (count << PAGE_SHIFT); > > > > > > It's best to put all calculations (including shifts) in the print part, > > > as that's the slow path. The TP_fast_assign() is done when the trace > > > point is triggered (during the execution of the code). It's best to > > > keep this in the slow path (TP_printk). > > > > > > __entry->count = count; > > > > > > > + ), > > > > + > > > > + TP_printk("member=%d size=%ldB", > > > > + __entry->member, > > > > + __entry->size) > > > > > > __entry->count << PAGE_SHIFT) > > > > Ah. Android users now use a tool called perfetto which gather raw trace > > (binary format). So such shifting will have to be done by userspace then if > > we did it this way. And I'm afraid this patch has been in circulation for > > quite some time now that may cause major pains in changing userspace tooling > > now :-\ > > > > I've been trying to get libtraceevent into a standard library, and > it's been ready to go. Can your tool please use that. It can handle this > without issue. Just feed it the format file (that's exported to > user space via the tracefs file system). I would love for that to happen but I don't develop Perfetto much. If I am writing a tool I will definitely give it a go from my side. CC'ing Perfetto's lead developer Primiano -- I believe you have already met Primiano at a conference before as he mentioned it to me that you guys met. I also believe this topic of using a common library was discussed before, but something about licensing came up. thanks, - Joel