我面临着由于过度使用内存而被杀死的问题sort，并且无法理解为什么它大大超出了给定的限制。
Context:
Available physical RAM: 8GB
Memory in use by system: <500MB (FreeBSD 13)
Free memory: ~7.5GB
Swap: 2G
No system hard limit on mem usage ($ ulimit -> unlimited)
File being sorted: 300+ GB
HDD space: 1Tb+ free both on target or temporary dir.
即使当我运行排序时指定可用资源限制；或者没有任何明确的参数（应自动设置为可用的 90%），它最终会因过度使用而被杀死。
[mario@casa-server ~/pjy]$ sort -S 7G -T /filesWD-WMAY03648941/tmp/ -o /filesWD-WMAY03648941/pjA-sorted.txt pjyA.txt
Killed
[mario@casa-server ~/pjy]$
[mario@casa-server ~/pjy]$ sort -T /filesWD-WMAY03648941/tmp/ -o /filesWD-WMAY03648941/pjA-sorted.txt pjyA.txt
Killed
[mario@casa-server ~/pjy]$
显然它确实超出了资源限制。当使用 -S 3G 运行时，我有时可以观察到大约 5G 的使用量。
# ~5G USAGE EVEN WITH EXPLICIT -S 3G LIMIT
[mario@casa-server ~]$ sudo procstat -r 3183
PID COMM RESOURCE VALUE
3183 sort user time 00:27:51.849171
3183 sort system time 00:03:28.220262
3183 sort maximum RSS 5423072 KB
3183 sort integral shared memory 10505728 KB
3183 sort integral unshared data 1910064 KB
3183 sort integral unshared stack 30560128 KB
3183 sort page reclaims 8172561
3183 sort page faults 1724
3183 sort swaps 0
3183 sort block reads 24296
3183 sort block writes 17719
3183 sort messages sent 0
3183 sort messages received 0
3183 sort signals received 0
3183 sort voluntary context switches 5868
3183 sort involuntary context switches 30700
[mario@casa-server ~]$
# TOP excerpt
PID USERNAME THR PRI NICE SIZE RES STATE C TIME WCPU COMMAND
3183 mario 1 103 0 4657M 4603M CPU3 3 38:23 99.88% sort -S 3G -T /filesWD-WMAY03648941/tmp/ -o /files
# NO SO LIMIT ON USAGE
[mario@casa-server ~]$ sudo procstat -l 3183
PID COMM RLIMIT SOFT HARD
3183 sort cputime infinity infinity
3183 sort filesize infinity infinity
3183 sort datasize 32768 MB 32768 MB
3183 sort stacksize 524288 KB 524288 KB
3183 sort coredumpsize infinity infinity
3183 sort memoryuse infinity infinity
3183 sort memorylocked 65536 B 65536 B
3183 sort maxprocesses 12186 12186
3183 sort openfiles 234576 234576
3183 sort sbsize infinity infinity
3183 sort vmemoryuse infinity infinity
3183 sort pseudo-terminals infinity infinity
3183 sort swapuse infinity infinity
3183 sort kqueues infinity infinity
3183 sort umtxp infinity infinity
[mario@casa-server ~]$
[mario@casa-server ~]$ ulimit
unlimited
这就解释了为什么它在以 7G 限制（7.5 可用）运行时被杀死，或者当限制被自动设置时：它确实超过了使用所有 mem+swap（并按预期被操作系统杀死）。
但我在这里缺少什么？man sort:
-S size, --buffer-size=size
Use size for the maximum size of the memory buffer. Size
modifiers %,b,K,M,G,T,P,E,Z,Y can be used. If a memory limit is
not explicitly specified, sort takes up to about 90% of available
memory. If the file size is too big to fit into the memory
buffer, the temporary disk files are used to perform the sorting.
如果-S 3G设置了，为什么会超过使用RAM而不是HDD临时文件夹？
PS：我试图问这个与其他“由于内存不足而被杀”相关的问题，但一些版主管理不善。我确实认为这是一个相关的问题（将其标记为不相关的问题只会使解决方案支离破碎）。另外，我阅读了许多其他可能的解决方案，但它们不适合这种情况。
谢谢大家