[Bug 252227] Default value of vm.max_wired is too low in 12.2

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https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=252227

            Bug ID: 252227
           Summary: Default value of vm.max_wired is too low in 12.2
           Product: Base System
           Version: 12.2-RELEASE
          Hardware: amd64
                OS: Any
            Status: New
          Severity: Affects Some People
          Priority: ---
         Component: kern
          Assignee: bugs at FreeBSD.org
          Reporter: vvd at unislabs.com

On 12.2 look like vm.max_wired is a hard limit for number of wired pages for
user processes.
With 48GB of RAM default value is 9727317 - it's 9727317*4096/1024/1024/1024 =
~37.1GB only.
Use case:
1) I see 9GB of free RAM
2) started VM in VirtualBox with 8GB
3) started applications in VM
4) VM freezes with VERR_NO_MEMORY error in VBox.log
5) stopped VM
6) 46*1024*1024*1024/4096 = 12058624
sysctl vm.max_wired=12058624
7) repeat 2) and 3)
8) VM work fine now

/usr/src/sys/vm/vm_pageout.c (2082):
vm_page_max_user_wired = 4 * freecount / 5;

>From dmesg: avail memory = 50130972672 (47808 MB)
47808 MB * 4/5/1024 = 37.35GB ~= 37.1GB

IMHO, it's very incorrect!
Something like 99/100 look more correct for VM servers with total RAM 48GB:
47808*99/100/1024 = 46.220625

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