switching from LFUDA to GDSF didn't make much of a difference. I assume the following is happening... I pre-cache around 2 to 3GB of data everyday and get 40 to 50% HITS everyday. Once the cache_dir size reaches the cache_swap_low threshold, squid is not aggressive enough in removing the old objects. Infact, I think squid is not doing anything to remove the old objects. So the pre-caching requests are not getting into the store and the HIT rate goes down big time. When this happens, if I increase the store size, I can see better HIT rates. What can be done to resolve this issue? Is there a equivalent of "reference_age" for squid V3.1.8? cache mgr always reports swap.files_cleaned = 0. my understanding is that this counter will show the # of objects removed from the disk store based on the replacement policy. I changed the cache_replacement_policy from "heap GDSF" to "lru" yesterday to see if it makes a difference. Removal policy: lru LRU reference age: 1.15 days issues with memory usage: both squids are running with 100% mem usage (15GB). Nothing else is running on these 2 servers. Stopping and starting the squid doesn't bring down the memory usage. The only way to release memory is to stop squid, move the cache dir to something_old, recreate and start squid with empty cache AND DELETE the old cache dirs. If I don't delete the old cache dir, memory is not getting released. squid runs in accel mode and serves only sqllite and xml files. nothing else. Squid Cache: Version 3.1.8 configure options: '--enable-icmp' '--enable-removal-policies=heap,lru' '--enable-useragent-log' '--enable-referer-log' '--enable-follow-x-forwarded-for' '--enable-default-hostsfile=/etc/hosts' '--enable-x-accelerator-vary' '--disable-ipv6' '--enable-htcp' '--enable-icp' '--enable-storeio=diskd,aufs' '--with-large-files' '--enable-http-violations' '--disable-translation' '--disable-auto-locale' '--enable-async-io' --with-squid=/root/downlaods/squid/squid-3.1.8 --enable-ltdl-convenience Please help. thanks. On Fri, Sep 24, 2010 at 1:16 PM, Rajkumar Seenivasan <rkcp613@xxxxxxxxx> wrote: > Hello Amos, > see below for my responses... thx. > >>>>> ? 50% empty cache required so as not to fill RAM? => cache is too big or RAM not enough. > cache usage size is approx. 6GB per day. > We have 15GB of physical memory on each box and the cache_dir is set for 20GB. > I had cache_swap_low 65 and cache_swap_high 70% and the available > memory went down to 50MB out of 15GB when the cache_dir used was 14GB > (reached the high threshold). > >>>>> What was the version in use before this happened? 3.1.8 okay for a while? or did it start discarding right at the point of upgrade from another? > We started testing with 3.1.6 and then used 3.1.8 in production. This > issue was noticed even during the QA. We didn't have any caching > servers before. > >>>>> Server advertised the content-length as unknown then sent 279307 bytes. (-1/279307) Squid is forced to store it to disk immediately (could be a TB >>>>> about to arrive for all Squid knows). > I looked further into the logs and the log entry I pointed out was > from the SIBLING request. sorry about that. > >>>>> These tell squid 50% of the cache allocated disk space MUST be empty at all times. Erase content if more is used. The defaults for these are less >>>>> than 100% in order to leave some small buffer of space for use by line-speed stuff still arriving while squid purged old objects to fit them. > Since our data changes every day, I don't need a cache dir with more > than 11GB to give enough buffer. On an average, 6GB of disk cache is > used per day. > >>>>> filesystem is resizerfs with RAID-0. only 11GB used for the cache. >>>>> Used or available? > 11GB used out of 20GB. > >>>>> The 10MB/GB of RAM usage by the in-memory index is calculated from an average object size around 4KB. You can check your available RAM roughly >>>>> meets Squid needs with: 10MB/GB of disk cache + the size of cache_mem + 10MB/GB of cache_mem + about 256 KB per number of concurrent clients at >>>>> peak traffic. This will give you a rough ceiling. > > Yesterday morning, we changed the cache_replacement_policy from "heap > LFUDA" to "heap GDSF", cleaned up the cache_dir and started squid > fresh. > > current disk cache usage is 8GB (out of 20GB). ie. after 30 hours. > Free memory is 1.7GB out of 15GB. > > Based on your math, the memory usage shouldn't be more than 3 or 4GB. > In this case, the used mem is far too high. > > > On Thu, Sep 23, 2010 at 12:21 AM, Amos Jeffries <squid3@xxxxxxxxxxxxx> wrote: >> On Wed, 22 Sep 2010 15:09:31 -0400, "Chad Naugle" >> <Chad.Naugle@xxxxxxxxxxx> >> wrote: >>> With that large array of RAM I would increase those maximum numbers, to >>> let's say, 8 MB, 16 MB, 32 MB, especially if you plan on using heap >> LFUDA, >>> which is optimized for storing larger objects, and trashes smaller >> objects >>> faster, where heap GSDF is the opposite, using LRU for memory for the >> large >>> objects to offset the difference. >>> >>> --------------------------------------------- >>> Chad E. Naugle >>> Tech Support II, x. 7981 >>> Travel Impressions, Ltd. >>> >>> >>> >>>>>> Rajkumar Seenivasan <rkcp613@xxxxxxxxx> 9/22/2010 3:01 PM >>> >>> Thanks for the tip. I will try with "heap GSDF" to see if it makes a >>> difference. >>> Any idea why the object is not considered as a hot-object and stored in >>> memory? >> >> see below. >> >>> >>> I have... >>> minimum_object_size 0 bytes >>> maximum_object_size 5120 KB >>> >>> maximum_object_size_in_memory 1024 KB >>> >>> Earlier we had cache_swap_low and high at 80 and 85% and the physical >>> memory usage went high leaving only 50MB free out of 15GB. >>> To fix this issue, the high and low were set to 50 and 55%. >> >> ? 50% empty cache required so as not to fill RAM? => cache is too big or >> RAM not enough. >> >>> >>> Does this change in "cache_replacement_policy" and the "cache_swap_low >>> / high" require a restart or just a -k reconfigure will do it? >>> >>> Current usage: Top >>> top - 14:33:39 up 12 days, 21:44, 3 users, load average: 0.03, 0.03, >> 0.00 >>> Tasks: 83 total, 1 running, 81 sleeping, 1 stopped, 0 zombie >>> Cpu(s): 0.0%us, 0.1%sy, 0.0%ni, 99.3%id, 0.0%wa, 0.0%hi, 0.0%si, >>> 0.6%st >>> Mem: 15736360k total, 14175056k used, 1561304k free, 283140k buffers >>> Swap: 25703960k total, 92k used, 25703868k free, 10692796k cached >>> >>> PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND >>> 17442 squid 15 0 1821m 1.8g 14m S 0.3 11.7 4:03.23 squid >>> >>> >>> #free >>> total used free shared buffers >> cached >>> Mem: 15736360 14175164 1561196 0 283160 >> 10692864 >>> -/+ buffers/cache: 3199140 12537220 >>> Swap: 25703960 92 25703868 >>> >>> >>> Thanks. >>> >>> >>> On Wed, Sep 22, 2010 at 2:16 PM, Chad Naugle <Chad.Naugle@xxxxxxxxxxx> >>> wrote: >>>> Perhaps you can try switching to heap GSDF, instead of heap LFUDA. >> What >>>> are also your minimum_object_size versus your _maximum_object_size? >>>> >>>> Perhaps you can also try setting the cache_swap_low / high back to >>>> default (90 - 95) to see if that will make a difference. >>>> >>>> --------------------------------------------- >>>> Chad E. Naugle >>>> Tech Support II, x. 7981 >>>> Travel Impressions, Ltd. >>>> >>>> >>>> >>>>>>> Rajkumar Seenivasan <rkcp613@xxxxxxxxx> 9/22/2010 2:05 PM >>> >>>> I have the following for replacement policy... >>>> >>>> cache_replacement_policy heap LFUDA >>>> memory_replacement_policy lru >>>> >>>> thanks. >>>> >>>> On Wed, Sep 22, 2010 at 2:00 PM, Chad Naugle <Chad.Naugle@xxxxxxxxxxx> >>>> wrote: >>>>> What is your cache_replacement_policy directive set to? >>>>> >>>>> --------------------------------------------- >>>>> Chad E. Naugle >>>>> Tech Support II, x. 7981 >>>>> Travel Impressions, Ltd. >>>>> >>>>> >>>>> >>>>>>>> Rajkumar Seenivasan <rkcp613@xxxxxxxxx> 9/22/2010 1:55 PM >>> >>>>> I have a strange issue happening with my squid (v 3.1.8) >>>>> 2 squid servers with sibling - sibling setup in accel mode. >> >> What was the version in use before this happened? 3.1.8 okay for a while? >> or did it start discarding right at the point of upgrade from another? >> >>>>> >>>>> after running the squid for 2 to 3 days, the HIT rate has gone down. >>>>> from 50% HIT to 34% for TCP and from 34% HIT to 12% for UDP. >>>>> >>>>> store.log shows that even fresh requests are NOT getting stored onto >>>>> disk and getting RELEASED rightaway. >>>>> This issue is with both squids... >>>>> >>>>> store.log entry: >>>>> 1285176036.341 RELEASE -1 FFFFFFFF 7801460962DF9DCA15DE95562D3997CB >>>>> 200 1285158415 -1 1285230415 application/x-download -1/279307 >>>>> GET http://.... >>>>> requests have a max-age of 20Hrs. >> >> Server advertised the content-length as unknown then sent 279307 bytes. >> (-1/279307) Squid is forced to store it to disk immediately (could be a TB >> about to arrive for all Squid knows). >> >>>>> >>>>> squid.conf: >>>>> cache_dir aufs /squid/var/cache 20480 16 256 >>>>> cache_mem 1536 MB >>>>> memory_pools off >>>>> cache_swap_low 50 >>>>> cache_swap_high 55 >> >> These tell squid 50% of the cache allocated disk space MUST be empty at >> all times. Erase content if more is used. The defaults for these are less >> than 100% in order to leave some small buffer of space for use by >> line-speed stuff still arriving while squid purged old objects to fit them. >> >> The 90%/95% numbers were created back when large HDD were measured MB. >> >> 50%/55% with 20GB cache only makes sense if you have something greater >> than 250Mbps of new cachable HTTP data flowing through this one Squid >> instance. In which case I'd suggest a bigger cache. >> >> (My estimate of the bandwidth is calculated from: % of cache needed free / >> 5 minute interval lag in purging.) >> >> >>>>> refresh_pattern . 0 20% 1440 >>>>> >>>>> >>>>> filesystem is resizerfs with RAID-0. only 11GB used for the cache. >> >> Used or available? >> >> cache_dir...20480 = 20GB allocated for the cache. >> >> With 11GB is roughly 50% (cache_swap_low) of the 20GB. So that seems to be >> working. >> >> >> The 10MB/GB of RAM usage by the in-memory index is calculated from an >> average object size around 4KB. You can check your available RAM roughly >> meets Squid needs with: 10MB/GB of disk cache + the size of cache_mem + >> 10MB/GB of cache_mem + about 256 KB per number of concurrent clients at >> peak traffic. This will give you a rough ceiling. >> >> Amos >> >
