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change calculation for free; change version to 1.1.0
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@zfdang
zfdang committed Dec 31, 2023
1 parent caf80d6 commit e9ea635
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2 changes: 1 addition & 1 deletion Makefile
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Expand Up @@ -5,7 +5,7 @@
#

PKG = free-for-macos
VER = 1.0
VER = 1.1.0

CWD = $(shell pwd)
PREFIX ?= /usr/local
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36 changes: 27 additions & 9 deletions README.md
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Expand Up @@ -7,7 +7,7 @@ This utility is designed to act like 'free' on Linux systems. It is a tool for
```
❯ free -h
total used free cached app wired
Mem: 32.00 GB 17.31 GB 2.30 GB 14.40 GB 14.11 GB 2.09 GB
Mem: 32.00 GB 18.69 GB 337.48 MB 12.98 GB 15.48 GB 2.04 GB
Swap: 0.00 B 0.00 B 0.00 B
```

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```
❯ free -v
free: version 1.0
free: version 1.1.0
❯ free
total used free cached app wired
Mem: 34359738368 18562465792 2487943168 15471935488 15431581696 1932247040
Mem: 34359738368 20060241920 282902528 14016593920 16661561344 2149351424
Swap: 0 0 0
❯ free -h
total used free cached app wired
Mem: 32.00 GB 17.31 GB 2.30 GB 14.40 GB 14.11 GB 2.09 GB
Mem: 32.00 GB 18.69 GB 337.48 MB 12.98 GB 15.48 GB 2.04 GB
Swap: 0.00 B 0.00 B 0.00 B
❯ free -h -s 1
total used free cached app wired
Mem: 32.00 GB 17.30 GB 2.31 GB 14.41 GB 14.31 GB 1.87 GB
Mem: 32.00 GB 18.67 GB 344.30 MB 12.99 GB 15.48 GB 2.03 GB
Swap: 0.00 B 0.00 B 0.00 B
total used free cached app wired
Mem: 32.00 GB 17.31 GB 2.30 GB 14.41 GB 14.14 GB 2.05 GB
Mem: 32.00 GB 18.66 GB 336.53 MB 13.02 GB 15.42 GB 2.07 GB
Swap: 0.00 B 0.00 B 0.00 B
total used free cached app wired
Mem: 32.00 GB 17.31 GB 2.30 GB 14.41 GB 14.16 GB 2.03 GB
Mem: 32.00 GB 18.68 GB 337.17 MB 12.99 GB 15.48 GB 2.04 GB
Swap: 0.00 B 0.00 B 0.00 B
total used free cached app wired
Mem: 32.00 GB 17.31 GB 2.30 GB 14.41 GB 14.16 GB 2.03 GB
Mem: 32.00 GB 18.65 GB 343.44 MB 13.02 GB 15.42 GB 2.06 GB
Swap: 0.00 B 0.00 B 0.00 B
^C
```
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# Explanation:

Total memory is fetched from host_info.

`https://developer.apple.com/documentation/kernel/1502514-host_info`

All other memory information is fetched from host_statistics64.

`https://developer.apple.com/documentation/kernel/1502863-host_statistics64`

Here are the methods to calculate memory statistics:

## free memory

```
// free = free_count - speculative_count; verified
formatBytes((vm_stat.free_count - vm_stat.speculative_count) * page_size, mem.free, sizeof(mem.free), human);
```

## used memory
```
// truely-free = free-count - speculative_count
// used = total - truely-free - cached; partially verified, still small discrepancy
// used = total - truely-free - cached; partially verified, still has small discrepancy with "activity monitor"
formatBytes(hbi.max_mem - (vm_stat.free_count - vm_stat.speculative_count + vm_stat.purgeable_count + vm_stat.external_page_count) * page_size, mem.used, sizeof(mem.used), human);
```

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4 changes: 2 additions & 2 deletions free.c
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Expand Up @@ -161,8 +161,8 @@ int main(int argc, char **argv) {
/* we have collected data, put it into our structure */
// total; verified
formatBytes(hbi.max_mem, mem.total, sizeof(mem.total), human);
// free; verified
formatBytes(vm_stat.free_count * page_size, mem.free, sizeof(mem.free), human);
// free = free_count - speculative_count; verified
formatBytes((vm_stat.free_count - vm_stat.speculative_count) * page_size, mem.free, sizeof(mem.free), human);
// wired; verified
formatBytes(vm_stat.wire_count * page_size, mem.wired, sizeof(mem.wired), human);
// cached file = purgeable_count + external_page_count; verified
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