[squid-users] SMP and AUFS

[Alex Rousskov]

On 03/30/2017 02:43 AM, Matus UHLAR - fantomas wrote:
>> On 03/20/2017 10:15 AM, Matus UHLAR - fantomas wrote:
>>> Well, I personally will still be curious how much does SMP affect the
>>> case of one worker and one or more diskers...
>
> On 20.03.17 12:19, Alex Rousskov wrote:
>> I do not understand why you are asking this question in AUFS context.
>> AUFS does not use diskers!

> because it's diskers (rock store) who switch to SMP mode when "workers
> 1" is used, and this may cause troubles to *ufs.

Diskers do not cause trouble -- they are doing exactly what they have 
been designed to do. It is ufs (being SMP-unaware) that causes trouble 
in SMP mode when admins enable ufs-based cache_dirs in SMP configurations.


>> Diskers primary function is low-level disk cache I/O. Like all kids,
>> diskers respond to cache manager requests and Squid management events
>> (e.g. shutdown and reconfiguration). IIRC, diskers also build in-RAM
>> cache_dir index.
>>
>>    http://wiki.squid-cache.org/Features/SmpScale#Terminology

> their own or also the shared one?

Their own, which is shared among all workers. In many contexts, one can 
view the set of all disk-specific shared indexes as one big shared disk 
index. Please note that my recollection that diskers build the in-RAM 
cache_dir index may be wrong -- this behavior may have changed, and I 
have not checked the code or commit logs. It would certainly make sense 
for diskers to build their indexes, but I do not remember whether we 
have implemented that optimization.


HTH,

Alex.