Plans to support ARM64 as architecture? about tcmalloc HOT 5 CLOSED

Hello, I have just compiled snort 3.1 on Arm64 machine
snort_strace_tmalloc.txt
with tcmalloc enabled, the snort binary won't run, it is stuck see attached log file.
without tcmalloc enabled, it works fine.

any idea?

from tcmalloc.

NOTE: I am building currently with the SMALL_BUT_SLOW option on because I first thought maybe the default 1GB mapping was causing the issue, but I get the same problem with either option.

from tcmalloc.

As a general note, ARM64 support would be desirable, but it's not yet ready. Our per-CPU cache implementation relies on hand-written assembly and needs to be ported to ARM.

Do you know how your page table is configured with your kernel build? https://kernel.org/doc/Documentation/arm64/memory.txt has a discussion of 39- versus 48-bit address spaces.

As an optimization, we "tag" (by using an upper bit of the pointer) sampled objects during allocation. The tag makes it easy to distinguish sampled objects from unsampled ones. My suspicion is that we are unable to allocate memory with the right bit pattern--possibly due to a constrained 39-bit address space--and so we fail. One way of testing this hypothesis is to edit tcmalloc/common.h's kAddressBits to 39 (instead of 48) for the ARM configuration.

from tcmalloc.

Thanks for the quick reply! Based on the boot output, I think it is using 39-bit addresses:

[    0.000000] Virtual kernel memory layout:
[    0.000000]     modules : 0xffffff8000000000 - 0xffffff8008000000   (   128 MB)
[    0.000000]     vmalloc : 0xffffff8008000000 - 0xffffffbebfff0000   (   250 GB)
[    0.000000]       .text : 0xffffff8008080000 - 0xffffff8008f60000   ( 15232 KB)
[    0.000000]     .rodata : 0xffffff8008f60000 - 0xffffff80095e0000   (  6656 KB)
[    0.000000]       .init : 0xffffff80095e0000 - 0xffffff8009e40000   (  8576 KB)
[    0.000000]       .data : 0xffffff8009e40000 - 0xffffff800a11b808   (  2927 KB)
[    0.000000]        .bss : 0xffffff800a11b808 - 0xffffff800a1b3dbc   (   610 KB)
[    0.000000]     fixed   : 0xffffffbefe7fd000 - 0xffffffbefec00000   (  4108 KB)
[    0.000000]     PCI I/O : 0xffffffbefee00000 - 0xffffffbeffe00000   (    16 MB)
[    0.000000]     vmemmap : 0xffffffbf00000000 - 0xffffffc000000000   (     4 GB maximum)
[    0.000000]               0xffffffbf00000000 - 0xffffffbf03fc8000   (    63 MB actual)
[    0.000000]     memory  : 0xffffffc000000000 - 0xffffffc0ff200000   (  4082 MB)

I'll give it a try to change the address bits and see if it works.

In the short term I'm interested in using tcmalloc for the heap profiling abilities, so even if the assembly code is not complete, do you expect tcmalloc to work functionally (albeit not at max performance) on ARM64?

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BTW, the change to 39-bits seems to work (at least for the hello_main test program). Going to try with our main application. If you think that it's likely we'll run into other problems given the not-officially-supported nature, please let me know. Thanks agian!

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