| perf-mem(1) |
| =========== |
| |
| NAME |
| ---- |
| perf-mem - Profile memory accesses |
| |
| SYNOPSIS |
| -------- |
| [verse] |
| 'perf mem' [<options>] (record [<command>] | report) |
| |
| DESCRIPTION |
| ----------- |
| "perf mem record" runs a command and gathers memory operation data |
| from it, into perf.data. Perf record options are accepted and are passed through. |
| |
| "perf mem report" displays the result. It invokes perf report with the |
| right set of options to display a memory access profile. By default, loads |
| and stores are sampled. Use the -t option to limit to loads or stores. |
| |
| Note that on Intel systems the memory latency reported is the use-latency, |
| not the pure load (or store latency). Use latency includes any pipeline |
| queuing delays in addition to the memory subsystem latency. |
| |
| On Arm64 this uses SPE to sample load and store operations, therefore hardware |
| and kernel support is required. See linkperf:perf-arm-spe[1] for a setup guide. |
| Due to the statistical nature of SPE sampling, not every memory operation will |
| be sampled. |
| |
| On AMD this use IBS Op PMU to sample load-store operations. |
| |
| COMMON OPTIONS |
| -------------- |
| -f:: |
| --force:: |
| Don't do ownership validation |
| |
| -t:: |
| --type=<type>:: |
| Select the memory operation type: load or store (default: load,store) |
| |
| -v:: |
| --verbose:: |
| Be more verbose (show counter open errors, etc) |
| |
| -p:: |
| --phys-data:: |
| Record/Report sample physical addresses |
| |
| --data-page-size:: |
| Record/Report sample data address page size |
| |
| RECORD OPTIONS |
| -------------- |
| <command>...:: |
| Any command you can specify in a shell. |
| |
| -e:: |
| --event <event>:: |
| Event selector. Use 'perf mem record -e list' to list available events. |
| |
| -K:: |
| --all-kernel:: |
| Configure all used events to run in kernel space. |
| |
| -U:: |
| --all-user:: |
| Configure all used events to run in user space. |
| |
| --ldlat <n>:: |
| Specify desired latency for loads event. Supported on Intel, Arm64 and |
| some AMD processors. Ignored on other archs. |
| |
| On supported AMD processors: |
| - /sys/bus/event_source/devices/ibs_op/caps/ldlat file contains '1'. |
| - Supported latency values are 128 to 2048 (both inclusive). |
| - Latency value which is a multiple of 128 incurs a little less profiling |
| overhead compared to other values. |
| - Load latency filtering is disabled by default. |
| |
| REPORT OPTIONS |
| -------------- |
| -i:: |
| --input=<file>:: |
| Input file name. |
| |
| -C:: |
| --cpu=<cpu>:: |
| Monitor only on the list of CPUs provided. Multiple CPUs can be provided as a |
| comma-separated list with no space: 0,1. Ranges of CPUs are specified with - |
| like 0-2. Default is to monitor all CPUS. |
| |
| -D:: |
| --dump-raw-samples:: |
| Dump the raw decoded samples on the screen in a format that is easy to parse with |
| one sample per line. |
| |
| -s:: |
| --sort=<key>:: |
| Group result by given key(s) - multiple keys can be specified |
| in CSV format. The keys are specific to memory samples are: |
| symbol_daddr, symbol_iaddr, dso_daddr, locked, tlb, mem, snoop, |
| dcacheline, phys_daddr, data_page_size, blocked. |
| |
| - symbol_daddr: name of data symbol being executed on at the time of sample |
| - symbol_iaddr: name of code symbol being executed on at the time of sample |
| - dso_daddr: name of library or module containing the data being executed |
| on at the time of the sample |
| - locked: whether the bus was locked at the time of the sample |
| - tlb: type of tlb access for the data at the time of the sample |
| - mem: type of memory access for the data at the time of the sample |
| - snoop: type of snoop (if any) for the data at the time of the sample |
| - dcacheline: the cacheline the data address is on at the time of the sample |
| - phys_daddr: physical address of data being executed on at the time of sample |
| - data_page_size: the data page size of data being executed on at the time of sample |
| - blocked: reason of blocked load access for the data at the time of the sample |
| |
| And the default sort keys are changed to local_weight, mem, sym, dso, |
| symbol_daddr, dso_daddr, snoop, tlb, locked, blocked, local_ins_lat. |
| |
| -F:: |
| --fields=:: |
| Specify output field - multiple keys can be specified in CSV format. |
| Please see linkperf:perf-report[1] for details. |
| |
| In addition to the default fields, 'perf mem report' will provide the |
| following fields to break down sample periods. |
| |
| - op: operation in the sample instruction (load, store, prefetch, ...) |
| - cache: location in CPU cache (L1, L2, ...) where the sample hit |
| - mem: location in memory or other places the sample hit |
| - dtlb: location in Data TLB (L1, L2) where the sample hit |
| - snoop: snoop result for the sampled data access |
| |
| Please take a look at the OUTPUT FIELD SELECTION section for caveats. |
| |
| -T:: |
| --type-profile:: |
| Show data-type profile result instead of code symbols. This requires |
| the debug information and it will change the default sort keys to: |
| mem, snoop, tlb, type. |
| |
| -U:: |
| --hide-unresolved:: |
| Only display entries resolved to a symbol. |
| |
| -x:: |
| --field-separator=<separator>:: |
| Specify the field separator used when dump raw samples (-D option). By default, |
| The separator is the space character. |
| |
| In addition, for report all perf report options are valid, and for record |
| all perf record options. |
| |
| OVERHEAD CALCULATION |
| -------------------- |
| Unlike linkperf:perf-report[1], which calculates overhead from the actual |
| sample period, perf-mem overhead is calculated using sample weight. E.g. |
| there are two samples in perf.data file, both with the same sample period, |
| but one sample with weight 180 and the other with weight 20: |
| |
| $ perf script -F period,data_src,weight,ip,sym |
| 100000 629080842 |OP LOAD|LVL L3 hit|... 20 7e69b93ca524 strcmp |
| 100000 1a29081042 |OP LOAD|LVL RAM hit|... 180 ffffffff82429168 memcpy |
| |
| $ perf report -F overhead,symbol |
| 50% [.] strcmp |
| 50% [k] memcpy |
| |
| $ perf mem report -F overhead,symbol |
| 90% [k] memcpy |
| 10% [.] strcmp |
| |
| OUTPUT FIELD SELECTION |
| ---------------------- |
| "perf mem report" adds a number of new output fields specific to data source |
| information in the sample. Some of them have the same name with the existing |
| sort keys ("mem" and "snoop"). So unlike other fields and sort keys, they'll |
| behave differently when it's used by -F/--fields or -s/--sort. |
| |
| Using those two as output fields will aggregate samples altogether and show |
| breakdown. |
| |
| $ perf mem report -F mem,snoop |
| ... |
| # ------ Memory ------- --- Snoop ---- |
| # RAM Uncach Other HitM Other |
| # ..................... .............. |
| # |
| 3.5% 0.0% 96.5% 25.1% 74.9% |
| |
| But using the same name for sort keys will aggregate samples for each type |
| separately. |
| |
| $ perf mem report -s mem,snoop |
| # Overhead Samples Memory access Snoop |
| # ........ ............ ....................................... ............ |
| # |
| 47.99% 1509 L2 hit N/A |
| 25.08% 338 core, same node Any cache hit HitM |
| 10.24% 54374 N/A N/A |
| 6.77% 35938 L1 hit N/A |
| 6.39% 101 core, same node Any cache hit N/A |
| 3.50% 69 RAM hit N/A |
| 0.03% 158 LFB/MAB hit N/A |
| 0.00% 2 Uncached hit N/A |
| |
| SEE ALSO |
| -------- |
| linkperf:perf-record[1], linkperf:perf-report[1], linkperf:perf-arm-spe[1] |
