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Twenty years of Valgrind

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Re: Twenty years of Valgrind

#51

Post by abbeyj »

rigtorp wrote: post #16
syockit wrote: post #12

There are times when LeakSanitizer (in gcc-8.2) would not give me the full backtrace of a leak, while valgrind would, so to me it's still an indispensable tool for debugging leaks. One caveat is that it's magnitudes slower than valgrind. Now, if only I know how to make valgrind run as fast as LeakSanitizer... (command line options?)

You might need to add -fno-omit-frame-pointer to help ASAN unwind the stack.

This is definitely an option you want to be using when using ASan or LSan. You may also want to consider additionally using -momit-leaf-frame-pointer to skip frame pointers only in leaf functions while keeping frame pointers for non-leaf functions. This can make small leaf functions significantly shorter, limiting some of the negative impact of using -fno-omit-frame-pointer alone.

Sometimes even -fno-omit-frame-pointer won't help, like if the stack is being unwound through a system library that was built without frame pointers. In that case you can switch to the slow unwinder. Set the environment variable `ASAN_OPTIONS=fast_unwind_on_malloc=0` when running your program. But note that this will make most programs run significantly slower so you probably want to use it only when you really need it and not as the default setting for all runs.

Re: Twenty years of Valgrind

#52

Post by throwawaylinux »

harry8 wrote: post #43
cjbprime wrote: post #2

I wish I hadn't read this article because now I know that I've been mispronouncing Valgrind for nearly 20 years but I'm not going to stop. (Kidding. Thanks for Valgrind! I still use it for assessing memory corruption vulnerabilities along with ASan.)

I was introduced to valgrind by Andrew Tridgell during the main content of a vaguely famous lecture he gave that finished with the audience collectively writing a shellscript bitkeeper client [1] demonstrating beyond doubt that Tridge had not in any way acted like a "git" when bitkeeper's licenseholder pulled the license for the linux kernel community. Tridge said words to the effect "if you program in C and you don'…

Tridgell is possibly the most intelligent person I've ever met, and I've met Torvalds and a bunch of other Linux developers -- not that they aren't intelligent too, among them might be a challenger to that title.

Tridge has a way of explaining complicated ideas in a way that pares them down to their essence and helps you to understand them that just really struck me (a smart person is able to talk about a complicated thing in a way that makes you feel dumb, a really smart person is able to talk about a complicated thing in a way that makes you feel like a genius). As well as the ability and intellectual curiosity to jump seemingly effortlessly across disciplines.

And he's a fantastic and very entertaining public speaker. Highly recommend any talk he gives.

Re: Twenty years of Valgrind

#53

Post by mynegation »

atgreen wrote: post #42
mynegation wrote: post #18

I am old enough that I started with Purify and I used Valgrind starting from the version 1.0, because Purify was commercial and Solaris only. It saved my behind multiple multiple times.

Purify was an amazing tool. I recently noticed that one of my libraries (libffi) still has an --enable-purify configure option, although it probably hasn't been exercised in.. 20 years? A Purify patent prevented work-alikes for many years, but valgrind eventually emerged as a more-than-worthy successor. Fun fact: the creator of Purify went on to found Netflix and is still their CEO.

Ha! And I thought that the same person writing bzip2 and Val grind is my surprise for the day.

Re: Twenty years of Valgrind

#55

Post by cpeterso »

mynegation wrote: post #18

I am old enough that I started with Purify and I used Valgrind starting from the version 1.0, because Purify was commercial and Solaris only. It saved my behind multiple multiple times.

And BoundsChecker was also great!

https://en.m.wikipedia.org/wiki/BoundsChecker

Re: Twenty years of Valgrind

#57

Post by dietr1ch »

cjbprime wrote: post #2

I wish I hadn't read this article because now I know that I've been mispronouncing Valgrind for nearly 20 years but I'm not going to stop. (Kidding. Thanks for Valgrind! I still use it for assessing memory corruption vulnerabilities along with ASan.)

Now you are really on track to mispronounce Valgrind for nearly 21 years :P

Re: Twenty years of Valgrind

#58

Post by BeefWellington »

andrewf wrote: post #17
vlmutolo wrote: post #3

> I still use Cachegrind, Callgrind, and DHAT all the time. I’m amazed that I’m still using Cachegrind today, given that it has hardly changed in twenty years. (I only use it for instruction counts, though. I wouldn’t trust the icache/dcache results at all given that they come from a best-guess simulation of an AMD Athlon circa 2002.) I'm pretty sure I've seen people using the icache/dcache miss counts from valgrind…

https://sqlite.org/cpu.html#microopt - Cachegrind is used to measure performance because it gives answers that are repeatable to 7 or more significant digits. In comparison, actual (wall-clock) run times are scarcely repeatable beyond one significant digit [...] The high repeatability of cachegrind allows the SQLite developers to implement and measure "microoptimizations". There's a bunch of ways for caches to behave…

I would guess yes, just based on the L1/L2 (later L3) use and sizing between all those systems. 2002 vs 2022 is K8 vs 5800X3D for AMD, so you're looking at having 1 core and 64+64KB of L1 cache, 512KB of L2 cache[1] vs 8 cores (+ht) and 32+32KB L1 per core, 512KB L2 per core, 96MB L3.

Just managing the cache access between L2 and L3 I think would be additional consideration, but then you have to consider the actual architectural differences and on server chips locality will matter quite a bit.

[1]: https://en.wikipedia.org/wiki/Athlon_64

Re: Twenty years of Valgrind

#60

Post by snovv_crash »

mynegation wrote: post #53
atgreen wrote: post #42

Earlier quoted context omitted.

Purify was an amazing tool. I recently noticed that one of my libraries (libffi) still has an --enable-purify configure option, although it probably hasn't been exercised in.. 20 years? A Purify patent prevented work-alikes for many years, but valgrind eventually emerged as a more-than-worthy successor. Fun fact: the creator of Purify went on to found Netflix and is still their CEO.

Ha! And I thought that the same person writing bzip2 and Val grind is my surprise for the day.

And Ardupilot
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