On lör, 2008-07-05 at 12:44 -0300, Michel wrote: > I am not understanding why you keep suggesting single core as preferred cpu Did I? Not what I can tell. I said Squid uses only one core. > even if squid's core is actually not multi-thread capable a faster cpu is better - > there are also other things running on a machine so a smp machine ever is a benefit > to overall performance Both yes and no. For an application like Squid you will find that nearly all OS:es gets bound to a single core running both networking and the application, leaving the other cores to run various tiny other stuff.. > modern OS also should give squid's aufs threading benefits but I am not totally aufs isn't very cpu hungry. It's main purpose is to be able to exploit the parallellism there is in the harddrive hardware. The Squid cache function gets quite seek intensive so there is a huge benefit of being able to have multiple concurrent I/O operations (especially open/create calls...). diskd also isn't very cpu hungry. In fact probably a bit less than aufs. But diskd can not push the drives as far as aufs, and is still plauged some instability issues.. Why I recommend dual core instead of quad core is simply because you get a faster core speed in dual core than quad core for the same price (and often availability as well..) which will directly benefit Squid in high performance. Yes, Squid quite easily gets CPU bound, and is then limited to the core speed of your CPU, and the faster the core speed is the better in that situation. Selecting a slower core speed to fit more cores hurts performance for Squid when the server is mainly for Squid. > sure about your design here but at least diskd when running several diskd processes > is getting benefits from multicore cpus - and a lot and if you do not believe it > set up squid/disk on a 8-core machine and compare with 1|2|4|8 or more diskds to > your single-core-cpu-thing and measure it, in fact you do not even measure it, you > can see it and smell it ... You are welcome to give numbers proving that for Squid a 4 core system outperforms a 2 core system with the exact same configuration in all other aspects. Don't forget to include price in the matrix.. The most interesting test configurations is - no disk cache - single drive for disk cache - 4 drives for disk cache Until I see any numbers indicating quad core gives a significant increase outperforming what the same price configuration using dual core I will continue propagating that quad core is not beneficial to Squid. Similarly for dual core vs single core, but it's not as clear cut as there is not a big per core performance difference between single and dual core compared to prices.. Regards Henrik
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