Thanks Amos, Eliezer and Markus for your replies! @Eliezer: The server has 2 X 2.7 GHz CPUs, each with 12 cores. Squid version is 3.3.7 compiled from source and I'm running only one squid worker. @Marcus: What is maximum process size that TLB can address? Is it tunable? My operating system is CENTOS 6.4 with Kernel 2.6.34. @Amos: Please see my comments below: ----- Original Message ----- From: Amos Jeffries <squid3@xxxxxxxxxxxxx> To: squid-users@xxxxxxxxxxxxxxx Cc: Sent: Wednesday, July 24, 2013 9:58 PM Subject: Re: Squid Memory and Page Faults On 25/07/2013 1:05 a.m., Golden Shadow wrote: >> Hi there! >> >> My squid is installed on a server with 192 GB of RAM. I have the following directives in squid.conf: >> >> cache_mem 143360 MB >> maximum_object_size_in_memory 300 KB >> memory_replacement_policy heap GDSF >> >> memory_pools on >> memory_pools_limit 1024 MB >> >> ipcache_size 2048 >> ipcache_low 90 >> ipcache_high 95 >> >> fqdncache_size 2048 >> >> >> >> top reports that my squid process size is 20GB, which is far less than my RAM size, >> but nevertheless I still find some page faults (about 70 page faults over 2 hours). >> I'm wondering how could those page faults are occurring while squid process size is far >> less than my RAM size. How can I eliminate those time consuming page faults? >Two things here. > >Why is the process size only 20GB? you have a 143GB memory cache as part >of that RAM consumption by Squid. Perhapse your traffics real caching >requirement is far smaller than you are allowing storage for. Well, according to cache manager my squid RSS reached 173 GB at some time! >What exactly is the page faulting comign from though ... Squid or the OS? How can I tell? Cache manager itself reports these page faults, so I guess they are coming from squid. >If it is Squid, why would the OS have swapped that piece of memory out >to VM in the first place? perhapse something else is needing a chunk of >memory larger than Squid leaves available? I'm puzzled as well! I don't have any other process on that server that would take more than a few MBs! Do you think if I swapoff my swap, I could eliminate these page faults? After all, I have enough physical memory to run the server without swap. >> My second question, am I using correct values for the memory-related directives mentioned above? >> If no, I would really appreciate if you could suggest the correct values. >Any values you want are "correct", so long as they fit within the >machines limits and do not lead to the system swapping. I see, what would you recommend for memory_pools_limit on a server with 192 GB of RAM? >> My last question is about read_ahead_gap, whose default value is only 16 KB. >> Would increasing this value to let's say 32 KB or 64 KB increase the performance >> since I have high RAM on the server? >Perhapse. That is a buffer size more related to your network speed. Each >concurrent connection consumes up to that much RAM for buffers. If you >have clients that can drain 32KB or 64KB fast enough not to cause waves >or bursts in traffic it can be worthwhile raising it a bit. If you have >slow clients the reverse can be true. >Amos Best regards, Firas
