Re: [squid-users] Re: How much disk space is reclaimed by the cache replacement algorithms?

RW wrote:
> On Wed, 23 Dec 2009 17:58:41 +0100
> Matus UHLAR - fantomas <uhlar_at_fantomas.sk> wrote:
>
>
>
>>> 1. How often is the replacement done?
>>>
>> when the percentage of configured cache_dir size crosses the
>> cache_swap_high value.
>>
>
> I haven't looked at the code for a long-time and I only looked at 2.x,
> but cache_swap_high didn't seem to play any part that I could see.
> It's certainly not a simple high/low watermark algorithm.
>
> If you run a low-volume cache the percentage never budges
> from cache_swap_low (give or take a few objects), and if you shrink the
> cache size a little, it corrects within a couple of minutes, whether
> or not you hit the new cache_swap_high.
>

 From http://www.squid-cache.org/Doc/config/cache_swap_high/...

        The low- and high-water marks for cache object replacement.
        Replacement begins when the swap (disk) usage is above the
        low-water mark and attempts to maintain utilization near the
        low-water mark. As swap utilization gets close to high-water
        mark object eviction becomes more aggressive. If utilization is
        close to the low-water mark less replacement is done each time.

        Defaults are 90% and 95%. If you have a large cache, 5% could be
        hundreds of MB. If this is the case you may wish to set these
        numbers closer together.

Hope that helps clear it up.

Chris
Received on Wed Dec 23 2009 - 22:45:16 MST