Can you use jemalloc arenas to implement 32-bit pointers on a 64-bit architecture?

Asked Oct 15 '18 at 02:01

Active Oct 15 '18 at 18:26

Viewed 231 times

Is it possible to set up an arena with jemalloc that only allocates pages from a reserved 2^32 byte area of virtual memory

void* arena_start = 
       mmap(nullptr, 1ull<<32, 
            PROT_NONE, 
            MAP_PRIVATE | MAP_ANONYMOUS, 
            -1, 0);

so that any pointer allocated from the arena with mallocx using the MALLOCX_ARENA option for the arena can be represented as a 32-bit index from arena_start.

The motivation for this is pointer compression for more space-efficient data structures. (See the paper Tranparent Pointer Compression for Linked DataStructures for background on similar use cases.)

The comments from this thread on arenas make me think this type of customization may be supported.

edited Oct 15 '18 at 18:26

asked Oct 15 '18 at 02:01

Ryan Burn

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@M.M - good point. I made a correction. – Ryan Burn Oct 15 '18 at 02:49
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Note: your *client* code probably has alignment requirements, so you could scale down index by sizeof (alignment); probably 8. – joop Oct 15 '18 at 15:45

Can you use jemalloc arenas to implement 32-bit pointers on a 64-bit architecture?

0 Answers0