tcp: even localhost networking is extremely slow sometimes

[X512]

This is hrev57460.

Server:

python3 -m http.server --bind 0.0.0.0 80

Client:

/Haiku/data/distrib> wget -O - http://127.0.0.1/Fedora-Workstation-Live-x86_64-38-1.6.iso > /dev/null
--2023-12-29 05:51:44--  http://127.0.0.1/Fedora-Workstation-Live-x86_64-38-1.6.iso
Connecting to 127.0.0.1:80... connected.
HTTP request sent, awaiting response... 200 OK
Length: 2099451904 (2.0G) [application/octet-stream]
Saving to: 'STDOUT'

-                                0%[                                                  ]   4.44M   284KB/s    eta 2h 0m  

DD for reference:

/Haiku/data/distrib> dd if=/Haiku/data/distrib/Fedora-Workstation-Live-x86_64-38-1.6.iso of=/dev/null bs=1M
2002+1 records in
2002+1 records out
2099451904 bytes (2.1 GB, 2.0 GiB) copied, 0.199473 s, 10.5 GB/s

[waddlesplash]

Related: #12876, #18203.

[X512]

After patchset (​https://review.haiku-os.org/c/haiku/+/7285/1) applied:

/boot/data/distrib> wget -O - http://127.0.0.1/Fedora-Workstation-Live-x86_64-38-1.6.iso > /dev/null
--2023-12-31 12:03:59--  http://127.0.0.1/Fedora-Workstation-Live-x86_64-38-1.6.iso
Connecting to 127.0.0.1:80... connected.
HTTP request sent, awaiting response... 200 OK
Length: 2099451904 (2.0G) [application/octet-stream]
Saving to: ‘STDOUT’

-                         100%[=====================================>]   1.96G   596MB/s    in 3.5s    
-                               100%[====================================================>]   1.96G   263MB/s    in 7.6s    
-                                    100%[=====================================================================>]   1.96G   493MB/s    in 4.1s    
-                                    100%[=====================================================================>]   1.96G  45.3MB/s    in 45s     
-                                    100%[=====================================================================>]   1.96G   656MB/s    in 3.1s    
-                                    100%[=====================================================================>]   1.96G   860MB/s    in 2.3s    
-                                    100%[=====================================================================>]   1.96G   558MB/s    in 3.6s    
-                                    100%[=====================================================================>]   1.96G   536MB/s    in 3.7s    
-                                    100%[=====================================================================>]   1.96G   929MB/s    in 2.2s    
-                                    100%[=====================================================================>]   1.96G   221MB/s    in 9.0s    

[waddlesplash]

Merged in hrev57492. An 160x-3200x improvement is nothing to scoff at, to be sure; even if it's still inconsistent and more can be done.