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

[Alex Rousskov]

On 1/25/22 6:14 PM, André Bolinhas wrote:
> I need about 2M filedescriptors 

File descriptors are local to each Squid process. A single Squid process
(e.g., SMP worker) is unlikely to be able to handle 2 million concurrent
connections or similar resources. Keep that in mind when configuring
Squid and OS.


> so my squid is compiled with --enable-poll and --enable-epoll.
> In this case which mechanism Squid will use poll or epoll?

On Linux, use epoll. In most cases, it will be used by default, but if
you want to be absolutely sure, use --enable-epoll. Do not (explicitly)
enable things you do not need or do not know about, like --enable-poll.


> Also, for better performance for large FD, which mechanism did you recommend
> poll, epoll or kqueue?

On Linux, use epoll. It will be used by default in most Linux cases.


HTH,

Alex.


> -----Mensagem original-----
> De: squid-users <squid-users-bounces at lists.squid-cache.org> Em Nome De Amos
> Jeffries
> Enviada: 25 de janeiro de 2022 20:17
> Para: squid-users at lists.squid-cache.org
> Assunto: Re: [squid-users] [ext] Re: Absolute upper limit for
> filedescriptors in squid-6?
> 
> 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 for getrlimit... 
>> yes checking for setrlimit... yes 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).
> 
> 
> 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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