[squid-users] SMP mode, workers, cache_dir with conditional

[Alex Rousskov]

On 10/10/2018 09:10 AM, Amos Jeffries wrote:
> On 11/10/18 3:01 AM, juju wrote:
>> Hello,
>> Sorry if this question has already been posted ( I can't check as the
>> "Search Function" is currently not working )
>> I'm running squid-3.5.20 on Amazon Linux 2018.03. 2 cores with 8 GB
>> My squid is currently working but only on 1 core.
>> I which to use the 2 cores. I understood that I have to use workers in
>> squid.conf with separate cache directory.

> This is not quite correct.

> Per-worker configuration is only required for features which are not yet
> SMP-aware.


Just a couple of additional clarifications, not contradicting what Amos
has said:


> The rock cache type *is* SMP-aware, so one directory can be shared by
> workers.

"can be" and "must be". We do not support worker-specific cache_dirs.

In case of rock cache_dirs, I do not know for sure what would happen if
cache_dirs are configured on a per-worker basis, but I suspect that
there will be no disker processes to serve them. At best, you will get
no disk caching at all.


> The UFS/AUFS/diskd cache types are not SMP-aware yet, so they do need
> separate directories per-worker currently.

... but worker-specific cache_dirs are not supported, will violate HTTP
rules, etc.


> Since you are using only rock type caches you do not have to do anything
> special for SMP to work.

... with your simple configuration that does not use SMP-unaware features.

In fact, with rock cache_dirs, you do not even have to specify multiple
workers to get SMP Squid -- by default, Squid will run in SMP mode if
you have one worker (default) and at least one rock cache_dir. However,
multiple workers may be necessary to better utilize multicore CPUs.

Beware of hyperthreading: Do not expect two workers, each showing 80+%
CPU utilization to be able to share a single physical CPU core
efficiently. I do not know whether your two cores are hyperthreaded or real.

N.B. To search the mailing list archives, consider using your favorite
search engine. Many would accept a site:lists.squid-cache.org restriction.

Alex.