Messages in this thread | | | From | Namhyung Kim <> | Date | Tue, 9 Apr 2024 09:53:41 -0700 | Subject | Re: [PATCH 3/3] perf report: Add weight[123] output fields |
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Hi Kan,
On Tue, Apr 9, 2024 at 9:37 AM Liang, Kan <kan.liang@linux.intel.com> wrote: > > > > On 2024-04-08 8:06 p.m., Namhyung Kim wrote: > > Add weight1, weight2 and weight3 fields to -F/--fields and their aliases > > like 'ins_lat', 'p_stage_cyc' and 'retire_lat'. Note that they are in > > the sort keys too but the difference is that output fields will sum up > > the weight values and display the average. > > > > In the sort key, users can see the distribution of weight value and I > > think it's confusing we have local vs. global weight for the same weight. > > > > For example, I experiment with mem-loads events to get the weights. On > > my laptop, it seems only weight1 field is supported. > > > > $ perf mem record -- perf test -w noploop > > > > Let's look at the noploop function only. It has 7 samples. > > > > $ perf script -F event,ip,sym,weight | grep noploop > > # event weight ip sym > > cpu/mem-loads,ldlat=30/P: 43 55b3c122bffc noploop > > cpu/mem-loads,ldlat=30/P: 48 55b3c122bffc noploop > > cpu/mem-loads,ldlat=30/P: 38 55b3c122bffc noploop <--- same weight > > cpu/mem-loads,ldlat=30/P: 38 55b3c122bffc noploop <--- same weight > > cpu/mem-loads,ldlat=30/P: 59 55b3c122bffc noploop > > cpu/mem-loads,ldlat=30/P: 33 55b3c122bffc noploop > > cpu/mem-loads,ldlat=30/P: 38 55b3c122bffc noploop <--- same weight > > > > When you use the 'weight' sort key, it'd show entries with a separate > > weight value separately. Also note that the first entry has 3 samples > > with weight value 38, so they are displayed together and the weight > > value is the sum of 3 samples (114 = 38 * 3). > > > > $ perf report -n -s +weight | grep -e Weight -e noploop > > # Overhead Samples Command Shared Object Symbol Weight > > 0.53% 3 perf perf [.] noploop 114 > > 0.18% 1 perf perf [.] noploop 59 > > 0.18% 1 perf perf [.] noploop 48 > > 0.18% 1 perf perf [.] noploop 43 > > 0.18% 1 perf perf [.] noploop 33 > > > > If you use 'local_weight' sort key, you can see the actualy weight. > > > > $ perf report -n -s +local_weight | grep -e Weight -e noploop > > # Overhead Samples Command Shared Object Symbol Local Weight > > 0.53% 3 perf perf [.] noploop 38 > > 0.18% 1 perf perf [.] noploop 59 > > 0.18% 1 perf perf [.] noploop 48 > > 0.18% 1 perf perf [.] noploop 43 > > 0.18% 1 perf perf [.] noploop 33 > > > > But when you use the -F/--field option instead, you can see the average > > weight for the while noploop funciton (as it won't group samples by > > %s/funciton/function/ > > > weight value and use the default 'comm,dso,sym' sort keys). > > > > $ perf report -n -F +weight | grep -e Weight -e noploop > > # Overhead Samples Weight1 Command Shared Object Symbol > > 1.23% 7 42.4 perf perf [.] noploop > > I think the current +weight shows the sum of weight1 of all samples, > (global weight). With this patch, it becomes an average (local_weight). > The definition change may break the existing user script. > > Ideally, I think we should keep the meaning of the weight and > local_weight as is.
Hmm.. then we may add 'avg_weight' or something.
But note that there's a subtle difference in the usage. If you use 'weight' as a sort key (-s weight) it'd keep the existing behavior that shows the sum (global_weight). It'd show average only if you use it as an output field (-F weight).
The issue of the sort key is that it cannot have the total sum of weights for a function. It'll have separate entries for each weight for each function like in the above example.
Thanks, Namhyung
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