jemalloc
Hacker ApprovedThe most recommended of 4 memory allocators
Recommended as a drop-in malloc replacement that cuts memory use in long-running programs. Critics say it is a black box and trails newer allocators in multithreaded speed.
Recommended as a drop-in malloc replacement that cuts memory use in long-running programs. Critics say it is a black box and trails newer allocators in multithreaded speed.
45 people gave an opinion
- recommend it
- 34
- criticize it
- 11
- approval share
- 76%
Recommended in 6 of 13 months
- November 2025: recommended
- December 2025: not recommended
- January 2026: not recommended
- February 2026: recommended
- March 2026: recommended
- April 2026: not recommended
- May 2026: not recommended
- June 2026: recommended
- July 2026: not recommended
- August 2026: recommended
- September 2026: recommended
- October 2026: not recommended
- November 2026: not recommended (month in progress)
Owned for 8 years
Median of the 3 owners who said how long they have had it.
Each square is one year.
Why it carries the badge
- 34 people recommend itNeeds 10 or more, met.
- 3.1 recommenders for every criticNeeds 2 to 1 or better, met.
- Recommended in 6 of 13 monthsNeeds 4 or more, met.
The same three rules apply to every product, and the badge can’t be bought. How the badge works
What people say about it
The reasons people give, with the number of comments that give each one. Open a reason to read what they said.
Why people recommend it
Each mark is one comment
Cuts memory use sharply
“With jemalloc's reliable memory return settings, those problems disappear.”
Comment from 18 Sep 2026 in “Jemalloc 5.4.0” “jemalloc consistently used only about half of RAM as opposed to tcmalloc”
Comment from 17 Mar 2026 in “Jemalloc un-abandoned by Meta” “Switched to jemalloc and instantly memory stayed well below 1GB.”
Comment from 18 Sep 2026 in “Jemalloc 5.4.0” - Comment from 18 Sep 2026 in “Jemalloc 5.4.0”
- Comment from 17 Mar 2026 in “Jemalloc un-abandoned by Meta”
- Comment from 18 Sep 2026 in “Jemalloc 5.4.0”
- Comment from 18 Sep 2026 in “Comparison of Malloc() Algorithms”
Stable for long-running processes
“jemalloc seems to fragment and leak the least for processes running for months”
Comment from 16 Mar 2026 in “Jemalloc un-abandoned by Meta” “jemalloc saved my icinga2 installation that kept exploding in memory usage”
Comment from 17 Mar 2026 in “Jemalloc un-abandoned by Meta” “I've found jemalloc works best for long running libvips processes”
Comment from 1 Aug 2026 in “RipGrep musl binaries occasionally segfault during very-large searches” - Comment from 18 Sep 2026 in “Jemalloc 5.4.0”
Strong multithreaded allocation performance
“We used jemalloc for a while which helped since it allocates memory better for multithreaded applications”
Comment from 19 Feb 2026 in “Bridging Elixir and Python with Oban” “It always holds up in benchmarks against any new flavor of the month malloc that comes out.”
Comment from 16 Mar 2026 in “Jemalloc un-abandoned by Meta” Widely used, default on FreeBSD
“jemalloc has been the FreeBSD (released) default malloc implementation for the last 18.”
Comment from 28 Aug 2026 in “Don't use musl if you care about performance” “jemalloc is widely used and that’s why it makes sense to be aware of it”
Comment from 18 Sep 2026 in “Jemalloc 5.4.0”
What people warn about
Each mark is one comment
Large code size and complexity
“something like jemalloc generates 10x as much code as the rest of your app”
Comment from 4 May 2026 in “Embedded Rust or C Firmware? Lessons from an Industrial Microcontroller Use Case” “contrast to e.g. the complexity of jemalloc”
Comment from 12 Jul 2026 in “Understanding the Odin Programming Language” Lacks memory protections
“considering it OK to leak memory contents across a process boundary because it's within a cgroup sounds wild”
Comment from 17 Mar 2026 in “Jemalloc un-abandoned by Meta” “Using an allocator without memory protections in 2026”
Comment from 16 Mar 2026 in “Jemalloc un-abandoned by Meta”
Other memory allocators people recommend
The three most recommended other memory allocators, with the same counts for each, so you can compare like for like. The tick on each bar marks the 2 to 1 line the badge needs.
| Product | Recommend | Criticize | Approval | Months | Owned | Badge |
|---|---|---|---|---|---|---|
| jemallocThis page | 34 | 11 | 76% | 6 | 8 yrs3 owners | Approved |
| mimalloc | 22 | 7 | 76% | 9 | — | Approved |
| Bumpalo Rust crate | 8 | 2 | 80% | 5 | — | — |
| tcmalloc | 7 | 4 | 64% | 4 | — | — |
What people said
40 of the 51 comments that mention it, newest first. Each links to the original comment.
“plugging in mimalloc or jemalloc will be much less work, and much less error prone”
“with jemalloc its been dead stable for years”
“drastically reduces memory usage for the same workloads”
“Nice to see jemalloc active again.”
“because it has per-thread allocation counters”
“with jemalloc it no longer actually matters”
“Switched to jemalloc and instantly memory stayed well below 1GB.”
“the runtimes belonging to all or at least most of those languages perform a lot better with jemalloc than with the system default”
“memory dropped from 8gib to under 1gib”
“With jemalloc's reliable memory return settings, those problems disappear.”
“Changing the malloc to jemalloc solved the issue, even though initially it was done for its debugging capabilities.”
“We would not be able to run our workloads without Jemalloc.”
“It makes a huge difference for Ruby on Rails Apps.”
“I benefit from jemalloc in my stack (RoR)”
“jemalloc is widely used and that’s why it makes sense to be aware of it”
“because it was using way less memory”
“ended up using jemalloc after a few patches and bug fixes”
“jemalloc has been the FreeBSD (released) default malloc implementation for the last 18.”
“I've found jemalloc works best for long running libvips processes”
“contrast to e.g. the complexity of jemalloc”
“big general-purpose allocators like jemalloc or mimalloc are usually a bandaid to somewhat salvage a failed memory management strategy”
“the common solution is to use tcmalloc or jemalloc which hasnt these problems?”
“something like jemalloc generates 10x as much code as the rest of your app”
“Standard options like jemalloc and mimalloc are incredibly fast, but they act as black boxes.”
“jemalloc consistently used only about half of RAM as opposed to tcmalloc”
“Glad to see the commitment towards important non-LLM projects!”
“jemalloc saved my icinga2 installation that kept exploding in memory usage”
“because jemalloc got much better”
“Stuck with battle hardened jemalloc for now.”
“saw 15-20% memory reduction in our Python services”
“considering it OK to leak memory contents across a process boundary because it's within a cgroup sounds wild”
“Using an allocator without memory protections in 2026”
“If you changed from glibc to jemalloc and that solved your issues”
“It did saved us a lot of AWS costs”
“jemalloc seems to fragment and leak the least for processes running for months”
“It still beat mimalloc when I checked 4-5 years ago.”
“It always holds up in benchmarks against any new flavor of the month malloc that comes out.”
“We used jemalloc for a while which helped since it allocates memory better for multithreaded applications”
“modern allocators like mimalloc or jemalloc easily outperformed modern GCs of Java”
“We had good results using jemalloc this way.”
Counts come from 1,795,640 Hacker News comments, November 2025 to November 2026. How we count. Report a mistake.