[squid-users] Squid 3.5.20 rock store and enable-disk-io

[Alex Rousskov]

On 08/31/2016 02:46 AM, FredB wrote:

> I saw this in rock store documentation
> 
>         If possible, Squid using Rock Store creates a dedicated kid
>         process called "disker" to avoid blocking Squid worker(s) on disk
>         I/O. One disker kid is created for each rock cache_dir.  Diskers
>         are created only when Squid, running in daemon mode, has support
>         for the IpcIo disk I/O module.

The above sounds correct to me.


> OK so I'm trying now --enable-disk-io=yes and there no more disker
> process, I'm doing something wrong ?

Normally, you do not need any ./configure options to enable Rock
support, including support for a stand-alone disker process. If you want
to enable IpcIo explicitly, you may, but I would first check whether it
was enabled without any --enable-disk-io options:

> $ fgrep IpcIo config.log 
> configure:21195: Enabling IpcIo DiskIO module
> configure:21227: IO Modules built:  AIO Blocking DiskDaemon DiskThreads IpcIo Mmapped

IpcIo requires shared memory support bust most modern build environments
provide that.


> Perhaps this process is only created in smp mode ?

As the documentation tries to imply, the disker process is used when all
of the statements below are true:

* there are rock cache_dir(s) in squid.conf
* IpcIo disk I/O module is enabled (it usually is by default)
* Squid was started without the -N command line option.


HTH,

Alex.