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Mon, 02 Dec 2019 13:13:47 -0800 (PST) Received: from localhost ([2620:15c:6:12:9c46:e0da:efbf:69cc]) by smtp.gmail.com with ESMTPSA id l7sm436189pfl.11.2019.12.02.13.13.46 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 02 Dec 2019 13:13:46 -0800 (PST) Date: Mon, 2 Dec 2019 16:13:45 -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 Subject: Re: [patch 026/158] mm: emit tracepoint when RSS changes Message-ID: <20191202211345.GE17234@google.com> References: <20191201015030.MR-ux4mV1%akpm@linux-foundation.org> <20191202121415.1e64a461@gandalf.local.home> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20191202121415.1e64a461@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 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 would say lets leave it alone for this once! But that is a good idea. thanks, - Joel