My total hit ratio decreased in ~2 times from 40% to 20% (it could be cold cache but it lasted at this level for a day without sign of improvement).
I'll retry tests with making sure there're no Vary header and will also try 1 worker with shared cache tomorrow. But even if it is this bug looks like caching works as expected in squid 4 so it'll be better solution than messing up with headers probably. On Mon, Jan 15, 2018 at 10:26 AM, Alex Rousskov < rouss...@measurement-factory.com> wrote: > 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%. > > This could be a side effect of not supporting Vary caching in shared > memory: https://bugs.squid-cache.org/show_bug.cgi?id=3806#c9 > > > > And disk cache hit ratio went up from 15-50% to stable 60-65%. > > I hope your total/combined hit ratio improved overall. > > > > it looks like in SMP/rock mode squid avoids using memory for small > > files like 1-3KB but uses it for 10KB+ files. > > No, there is no such size-discrimination code in Squid. > > > > I started tracking down the issue with disabling disk cache completely > > and it didn't change anything, I just started to get MISS every time for > > the URL which was getting MEM_HIT with an old configuration. Then I > > changed "workers 2" to "workers 1" and started getting memory hits as > > before. > > For a clean apples-to-apples test, make sure you use > "memory_cache_shared on" when using a single worker without rock > cache_dirs. > > > > Am I doing anything wrong? Which debug options should I enable to > > provide more information if it seems like a bug? > > > Vary caching should be fixed as well, of course, but perhaps there is > another problem we do not know about. I would start by eliminating Vary > as the known problem. When using a test transaction, make sure the > response does not have a Vary header. Or configure Squid to log the Vary > header and remove the corresponding transactions when computing > adjusted-for-Vary memory cache hit ratio. > > > HTH, > > Alex. > -- With best regards, Ivan Larionov.
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