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I very recently used jemalloc to resolve a memory fragmentation issue that caused a service to OOM every few days. While jemalloc as it is will continue to work, same as it does today, I wonder what allocator I should reach for in the future. Does anyone have any experiences to share regarding tcmalloc or other allocators that aim to perform better than stock glibc?
I’ve wondered about this before but never when around people who might know. From my outsider view, jemalloc looked like a strict improvement over glibc’s malloc, according to all the benchmarks I’d seen when the subject came up. So, why isn’t it the default allocator?
There's also the fact that ... a lot of processes only ever have a single thread, or at most have a few background threads that do very little of interest. So all these "multi-threading-first allocators" aren't actually buying anything of value, and they do have a lot of overhead.
Semi-related: one thing that most people never think about: it is exactly the same amount of work for the kernel to zero a page of memory (in preparation for a future mmap) as for a userland process to zero it out (for its own internal reuse)
I wonder if you did get everything you should from the companies that use it. I mean sometimes I feel that big tech firms only use free software, never giving anything to it, so I hope you were the exception here.
I understand the decision to archive the upstream repo; as of when I left Meta, we (i.e. the Jemalloc team) weren’t really in a great place to respond to all the random GitHub issues people would file (my favorite was the time someone filed an issue because our test suite didn’t pass on Itanium lol). Still, it makes me sad to see. Jemalloc is still IMO the best-performing general-purpose malloc implementation that’s…
That was me that filed the Itanium test suite failure. :)
I understand the decision to archive the upstream repo; as of when I left Meta, we (i.e. the Jemalloc team) weren’t really in a great place to respond to all the random GitHub issues people would file (my favorite was the time someone filed an issue because our test suite didn’t pass on Itanium lol). Still, it makes me sad to see. Jemalloc is still IMO the best-performing general-purpose malloc implementation that’s…
Earlier quoted context omitted.
Stuff like this is what keeps me coming back here. Thanks for posting this! What's hard about using TCMalloc if you're not using bazel? (Not asking to imply that it's not, but because I'm genuinely curious.)
It’s just a huge pain to build and link against. Before the bazel 7.4.0 change your options were basically: 1. Use it as a dynamically linked library. This is not great because you’re taking at a minimum the performance hit of going through the PLT for every call. The forfeited performance is even larger if you compare against statically linking with LTO (i.e. so that you can inline calls to malloc, get the benefit o…
Switching to jemalloc instantly fixed an irksome memory leak in an embedded Linux appliance I inherited many moons ago. Thank you je, we salute you!
Nice post -- so does Facebook no longer use jemalloc at all? Or is it maintenance mode? Or I wonder if they could simply use tcmalloc or another allocator these days? Facebook infrastructure engineering reduced investment in core technology, instead emphasizing return on investment.
I’ve wondered about this before but never when around people who might know. From my outsider view, jemalloc looked like a strict improvement over glibc’s malloc, according to all the benchmarks I’d seen when the subject came up. So, why isn’t it the default allocator?
For a long time, one of the major problems with alternate allocators is that they would never return free memory back to the OS, just keep the dirty pages in the process. This did eventually change, but it remains a strong indicator of different priorities. There's also the fact that ... a lot of processes only ever have a single thread, or at most have a few background threads that do very little of interest. So all…
Earlier quoted context omitted.
I don't think that's really a position that can be defended. Both jemalloc and tcmalloc evolved and were refined in antagonistic multitenant environments without one overwhelming application. They are optimal for that exact thing.
It's possible that they were referring to something specific about their platform and its system allocator, but like I said it was an anecdote about one engineer's statement. I just remember thinking it sounded fair at the time.