[squid-users] [ext] Re: Absolute upper limit for filedescriptors in squid-6?

[Alex Rousskov]

On 1/25/22 15:17, Amos Jeffries wrote:
> On 26/01/22 03:55, Ralf Hildebrandt wrote:
>> * Francesco Chemolli:
>>> See configure --max-filedescriptors
>>
>> ...
>> configure: forcing default of 131072 filedescriptors (user-forced)
>> checking Default FD_SETSIZE value... 1024
>> checking Maximum number of filedescriptors we can open... 32768
>> configure: Default number of filedescriptors: 131072
>> ...
>>
>> Yes, I set "ulimit -n 131072" before running configure
>>
> 
> The ./configure has a 2^15 limit for the _default_ FD number. Runtime 
> should allow configuring larger values later (sans bugs).

In case it was not clear due to the presence of three(!) "defaults" in 
./configure output, the fourth "default" in Amos response is about the 
"Maximum number of filedescriptors we can open" line (that does not 
mention the word "default"): Squid just does not check whether it can 
open more than 32768 descriptors, regardless of --max-filedescriptors.

I hope somebody will change/fix the related ./configure functionality 
and/or message wording. Most humans will be confused by the 
self-contradictory output shared by Ralf. File descriptor limits is a 
complicated subject, but we can do better!


Cheers,

Alex.

> It also depends on the I/O module selected for runtime. Make sure you 
> avoid select(2) and poll(2) for large FD numbers.
> 
>   select(2) is limited to 1024.
>   poll(2) allows numbers large enough to hit RAM and CPU limits on speed.
>   epoll(2) is limited to ~3.5 million.
>   kqueue(2) is technically "unlimited" but YMMV regarding bugs etc.
> 
> 
> Amos
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