Re: [squid-users] Help Needed: Any suggestion on performance downgrade after enable Cache Digest?

Which OS?
If Linux, did you start looking at the CPU use using oprofile?

Adrian

On Mon, Apr 21, 2008, Zhou, Bo(Bram) wrote:
> Hi,
>
> Recently I did some interesting performance testing on the Squid configured
> with Cache Digest Enabled. The testing result shows that the Squid use more
> than 20% CPU time than the Squid running without Cache Digest. Following are
> my detailed testing environment and configuration and result. Anyone can
> give me some light on the possible reason will be greatly appreciated.
> Please also point out the possible configuration errors if any. Thanks a
> lot.
>
> 1. Hardware configuration : HP DL380
> (1) Squid Server
> CPU: 2 Xeon 2.8GHz CPUs, each Xeon CPU has 2 Cores
> Memory size: 6G, Disk: 36G, NIC: 1000M
> (2) Client and Web Server : Dell Vostro200 running with Web Polygraph 3.1.5
>
> 2. Squid Configuration
> (1) 2 Squid instances are running on the same HP server, each using same IP
> address but different PORT, pure in memory cache
> Squid1 configuration:
> http_port 8081
> cache_mem 1024 MB
> cache_dir null /tmp
> cache_peer 192.168.10.2 sibling 8082 0 proxy-only
> digest_generation on
> digest_bits_per_entry 5
> digest_rebuild_period 1 hour
> digest_swapout_chunk_size 4096 bytes
> digest_rebuild_chunk_percentage 10
>
> Squid2 configuration:
> http_port 8082
> cache_mem 1024 MB
> cache_dir null /tmp
> cache_peer 192.168.10.2 sibling 8081 0 proxy-only
> digest_generation on
> digest_bits_per_entry 5
> digest_rebuild_period 1 hour
> digest_swapout_chunk_size 4096 bytes
> digest_rebuild_chunk_percentage 10
>
> 3. 2 Polygraph Clients are used to send HTTP requests to Squid instances.
> Different client send request to different Squid instance. Each client
> configures 1000 users with 1.2 request/s, so totally each client send 1200
> requests/s.
>
> 4. Test result (Note: since 4 CPU used on the server, the total CPU
> utilization is 400%)
> (1) Running 2 Squid instances with Cache Digest Enabled, each handles 1200
> request/second:
> Each instance used ~95% CPU even during the time Squid didn't rebuild the
> digest
>
> (2) Running 2 Squid instances with Cache Digest Enabled, one handles 1200
> request/second, one is idle(no traffic to it)
> The one with traffic has CPU utilization ~65%, the other one is idle
>
> (3) Running 2 Squid instances with Cache Digest Disabled, each handles 1200
> request/second:
> Each instance used ~75% CPU
>
>
> Best Regards,
> Bo Zhou
>

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