On 01/16/2018 02:40 PM, Ivan Larionov wrote: > So it's definitely not related to Vary, there's no such header in > requests I tried. Just to avoid misunderstanding, please note that Vary is a response header. > Also this issue affects squid even with 1 worker if > shared memory is forced to on. This matches the current suspicion that there is something wrong with the shared memory cache (in your environment). > It's not like it makes any sense but how about random example url: > > http://techslides.com/demos/samples/sample.mp3 > > squid 4, 2 workers, shared cache, no disk cache – MEM_HIT > squid 3, same config – MISS every time > squid 3, no shared cache – MEM_HIT > > Could you do a brief test with this URL may be and confirm that I'm not > the only one who see this issue? I cannot confirm that: In primitive wget tests with Squid v3.5 (bzr r14182), I am getting shared memory hits with the above URL, with or without cache_dirs, with or without SMP. Alex. > On Tue, Jan 16, 2018 at 6:25 AM, Alex Rousskov wrote: > > On 01/15/2018 09:25 PM, Ivan Larionov wrote: > > My total hit ratio decreased in ~2 times from 40% to 20% > > > On 01/14/2018 10:53 PM, Ivan Larionov wrote: > > > > > After migrating squid from non-SMP/aufs to SMP/rock memory cache hit > > > ratio dropped significantly. Like from 50-100% to 1-5%. > > > > > And disk cache hit ratio went up from 15-50% to stable 60-65%. > > > The combination of the three statements above may be a sign of a problem > unrelated to Vary: Since the disk cache can cache everything the memory > cache can and is typically much larger than the memory cache, the > incapacitation of a memory cache (due to Vary) should not have a > significant effect on overall hit ratio. It should only affect hit > response time. > > The only known culprit I can think of in this context are hits for > being-cached objects: Rock lacks code that allows Squid to read > being-written objects. The shared memory cache has that code already. If > your workload has a lot of cases where clients request a being-written > object, then the overall hit ratio should go down after the memory cache > incapacitation (due to Vary). > > I suspect something else is in play here though, especially if you see a > different picture with Squid v4 -- the known problem discussed above is > present in all Squid versions. I second Amos's recommendation to focus > on v4 because it is unlikely that any complicated problems are going to > be fixed in v3, even if you triage them well. > > > HTH, > > Alex. > > > > > -- > With best regards, Ivan Larionov. _______________________________________________ squid-users mailing list squid-users@xxxxxxxxxxxxxxxxxxxxx http://lists.squid-cache.org/listinfo/squid-users
