[squid-users] 4 second Cache Miss Service Times

Dear All,

        I have recently set up a Squid cache using WCCP and a cisco router.
I am getting very impressive performance for my cache hits, but my cache
misses sometimes take as long as 4 seconds! We are at the end of a high
bandwidth, high latency satellite link with a normal latency (for example:
to google.com) of around 600ms round-trip. So why the 4 second delay?
Sometimes it comes down to 1.3sec but even that is a lot slower than I would
expect when my cache hits are being pumped out in 0.017s

        Any ideas?

        Here's my cachemanager stats (I've marked the relevant line with an
asterisk) :

Squid Object Cache: Version 2.5.STABLE9
Start Time: Thu, 15 Jun 2006 08:43:36 GMT
Current Time: Fri, 16 Jun 2006 07:14:09 GMT

Connection information for squid:
        Number of clients accessing cache: 46
        Number of HTTP requests received: 556986
        Number of ICP messages received: 0
        Number of ICP messages sent: 540
        Number of queued ICP replies: 0
        Request failure ratio: 0.00
        Average HTTP requests per minute since start: 412.4
        Average ICP messages per minute since start: 0.4
        Select loop called: 12369540 times, 6.551 ms avg
Cache information for squid:
        Request Hit Ratios: 5min: 33.2%, 60min: 30.2%
        Byte Hit Ratios: 5min: 10.9%, 60min: 16.3%
        Request Memory Hit Ratios: 5min: 6.2%, 60min: 8.9%
        Request Disk Hit Ratios: 5min: 28.7%, 60min: 27.1%
        Storage Swap size: 19916692 KB
        Storage Mem size: 102392 KB
        Mean Object Size: 13.80 KB
        Requests given to unlinkd: 0
Median Service Times (seconds) 5 min 60 min:
        HTTP Requests (All): 1.62803 1.71839
** Cache Misses: 3.11263 2.79397
        Cache Hits: 0.01745 0.01745
        Near Hits: 1.38447 1.24267
        Not-Modified Replies: 0.01164 0.01164
        DNS Lookups: 0.01535 0.02033
        ICP Queries: 0.00000 0.00000
Resource usage for squid:
        UP Time: 81033.414 seconds
        CPU Time: 2825.424 seconds
        CPU Usage: 3.49%
        CPU Usage, 5 minute avg: 8.78%
        CPU Usage, 60 minute avg: 8.15%
        Process Data Segment Size via sbrk(): 283308 KB
        Maximum Resident Size: 0 KB
        Page faults with physical i/o: 3
Memory usage for squid via mallinfo():
        Total space in arena: 283308 KB
        Ordinary blocks: 282627 KB 36898 blks
        Small blocks: 0 KB 0 blks
        Holding blocks: 11528 KB 6 blks
        Free Small blocks: 0 KB
        Free Ordinary blocks: 680 KB
        Total in use: 294155 KB 100%
        Total free: 680 KB 0%
        Total size: 294836 KB
Memory accounted for:
        Total accounted: 215351 KB
        memPoolAlloc calls: 79976881
        memPoolFree calls: 76613850
File descriptor usage for squid:
        Maximum number of file descriptors: 4096
        Largest file desc currently in use: 571
        Number of file desc currently in use: 433
        Files queued for open: 0
        Available number of file descriptors: 3663
        Reserved number of file descriptors: 100
        Store Disk files open: 0
Internal Data Structures:
        1446719 StoreEntries
         20863 StoreEntries with MemObjects
         20747 Hot Object Cache Items
        1443710 on-disk objects

Regards,

Ben Hathaway
Received on Fri Jun 16 2006 - 01:46:16 MDT