How does cachegrind work?

Cachegrind simulates how your program interacts with a machine’s cache hierarchy and (optionally) branch predictor. It simulates a machine with independent first-level instruction and data caches (I1 and D1), backed by a unified second-level cache (L2). This exactly matches the configuration of many modern machines.

How do you use Valgrind Cachegrind?

The two steps are:

1. Run your program with valgrind –tool=cachegrind in front of the normal command line invocation. When the program finishes, Cachegrind will print summary cache statistics.
2. Generate a function-by-function summary, and possibly annotate source files, using the supplied cg_annotate program.

What does callgrind measure?

Overview. Callgrind is a profiling tool that records the call history among functions in a program’s run as a call-graph. By default, the collected data consists of the number of instructions executed, their relationship to source lines, the caller/callee relationship between functions, and the numbers of such calls.

How do you use Valgrind for profiling?

To profile, you run your program under Valgrind and explicitly request the callgrind tool (if unspecified, the tool defaults to memcheck). Valgrind has written the information about the above 7 million collected events to an output file named callgrind.

What is Callgrind_annotate?

callgrind_annotate stops printing functions when the sum of the cost percentage of the printed functions for all the events is bigger or equal to the given event threshold percentages. When one or more thresholds are given via this option, the value of –threshold is ignored.

How slow is Callgrind?

When set to no , Callgrind will not be able to collect any information, including calls, but it will have at most a slowdown of around 4, which is the minimum Valgrind overhead. Instrumentation can be interactively switched on via callgrind_control -i on .

What is Valgrind written in?

C
Assembly language
Valgrind/Programming languages
Because Valgrind works directly with program binaries, it works with programs written in any programming language, be they compiled, just-in-time compiled, or interpreted. The Valgrind tools are largely aimed at programs written in C and C++, because programs written in these languages tend to have the most bugs!

How do you run Valgrind?

To run Valgrind, pass the executable as an argument (along with any parameters to the program). The flags are, in short: –leak-check=full : “each individual leak will be shown in detail” –show-leak-kinds=all : Show all of “definite, indirect, possible, reachable” leak kinds in the “full” report.

Why is it called Valgrind?

Valgrind was originally designed to be a free memory debugging tool for Linux on x86, but has since evolved to become a generic framework for creating dynamic analysis tools such as checkers and profilers. The name Valgrind is a reference to the main entrance of Valhalla from Norse Mythology.

How much slower is valgrind?

Valgrind uses a lot of memory, and programs run very slowly under it (25-50 times slower than natively).

How is cachegrind a cache and branch predictor?

Cachegrind simulates how your program interacts with a machine’s cache hierarchy and (optionally) branch predictor. It simulates a machine with independent first-level instruction and data caches (I1 and D1), backed by a unified second-level cache (L2). This exactly matches the configuration of many modern machines.

Which is the best description of cache associativity?

As such, fewer index bits are needed. Just as bookshelves come in different shapes and sizes, caches can also take on a variety of forms and capacities. But no matter how large or small they are, caches fall into one of three categories: direct mapped, n-way set associative, and fully associative.

What’s the difference between callgrind and cachegrind?

Callgrind and Cachegrind generate output that has a lot in common, like ‘time’ spent per function and line. The main differences are that Callgrind has more information about the callstack whilst cachegrind gives more information about cache hit rates.

Which is the most important extension of cachegrind?

The most important extension to the original format of Cachegrind is the ability to specify call relationship among functions. More generally, you specify assoziations among positions. For this, the second part of the file also can contain assoziation specifications. These look similar to position specifications, but consist of 2 lines.