[squid-users] --foreground vs -N

Alex Rousskov rousskov at measurement-factory.com
Wed Sep 18 20:14:13 UTC 2019

On 9/18/19 3:37 PM, B. Cook wrote:

> this is /dev/shm with --foreground (no workers)

> -rw-------  1 proxy proxy    8 2019-09-18 10:30 squid-cf__metadata.shm
> -rw-------  1 proxy proxy 8216 2019-09-18 10:30 squid-cf__queues.shm
> -rw-------  1 proxy proxy   36 2019-09-18 10:30 squid-cf__readers.shm

Your Squid is buggy: These collapsed forwarding shared memory segments
should not be created for non-SMP configurations. Using these collapsed
forwarding segments might slow down a non-SMP Squid instance, but I do
not know whether they are actually _used_. I suspect they are not.

The latest (future v5) Squid has the same bug AFAICT.

Unfortunately, in my future-v5 tests, the same or similar bug exists in
Squids started with -N, so this bug is probably not a good suspect in
your investigation. I have no other suspects to offer at this time.


> On Wed, Sep 18, 2019 at 2:38 PM Alex Rousskov wrote:
>> One thing you may want to check is whether your --foreground Squid is
>> creating shared memory segments (look in /dev/shm/ or equivalent).
>> Creating shared memory segments in non-SMP configurations is a bug.
>> IIRC, we have fixed one or two of those bugs, but there may be more, and
>> using shared memory tables can decrease performance of non-SMP
>> configurations (there is no free lunch).

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