[squid-users] Performance issue -- serving from cache

[Brad House]

On 2/15/26 8:00 PM, Alex Rousskov wrote:

> On 2026-02-14 14:45, Brad House wrote:
>> I've got a squid deployment where serving from cache can be slower 
>> than an uncached download.  I'm seeing speeds of around 50MB/s when 
>> serving from cache, which is much slower than anticipated.  Infact, 
>> when hitting fast upstream servers, serving of a non-cached asset is 
>> faster (even though its still hitting squid to fetch it).
>>
>> I'm thinking there's got to be something wrong with my squid 
>> configuration, I'm currently running on Rocky Linux 10 with Squid 
>> 6.10-6.
>>
>> The VM I'm using currently has 4 cores, 16G RAM and 100G of usable 
>> space.  I used fio to measure disk performance and I got
>>
>>   * Random Write: 3629MiB/s (1MB block), 33.2k (4k block) IOPS
>>   * Random Read: 8391MiB/s (1MB block), 43.5k (4k block) IOPS
>
>
> What speed to you get when Squid serves the object from the memory 
> cache? Do not configure a disk cache for this test to make sure that 
> Squid is not reading from disk...
>
> I cannot help with AUFS cache_dirs, but _if_ AUFS code uses 4KByte I/O 
> blocks, then 50MByte/s you are measuring is equivalent to 12K IOPS 
> which is arguably not that bad for that long-neglected AUFS code 
> (compared to "raw" 44K IOPS performance you measured with fio)!
>
> Please note that I am not trying to imply that rock cache_dir with a 
> large slot-size setting would work faster than AUFS. And even if 
> properly configured rock does work faster than AUFS, I would be really 
> surprised if Squid can approach Traffic Server performance! The two 
> projects had vastly different focus and resources.
>
>
> HTH,
>
> Alex.
>

I'll need to wait until the weekend to give the memory-only cache a 
try.  Do you have any suggested Rock settings I should try while I'm 
testing things?  I'm ok wasting disk space on smaller items if it means 
it can serve from cache faster in general.

Thanks.

-Brad