Summary: | New option for filters: run only if there are spare CPU cycles | ||
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Product: | Apache httpd-2 | Reporter: | Dan Harkless <apache-issues> |
Component: | mod_deflate | Assignee: | Apache HTTPD Bugs Mailing List <bugs> |
Status: | NEW --- | ||
Severity: | enhancement | ||
Priority: | P2 | ||
Version: | 2.5-HEAD | ||
Target Milestone: | --- | ||
Hardware: | All | ||
OS: | All |
Description
Dan Harkless
2006-12-05 19:08:35 UTC
An interesting suggestion. Are you aware of mod_load_average, which does a similar job for handlers? Your comment about mod_deflate could apply to other filters in a similar manner, and a load_average check could apply in mod_filter. Why isn't there a bugzilla entry for mod_filter? The difficulty here (as in mod_load_average) is a cross-platform way to define load. Also, bear in mind mod_cache for your own purposes. I agree with Nick. We should aim for a general solution here that could be used via mod_filter. In my experience CPU usage is only usable if you use an average value of CPU usage over a reasonable amout of time. Otherwise you just get unreasonable flip flops. Thats why I would regard load average as more reliable. But as Nick pointed out there is a problem to define and measure load platform independently. BTW: Shouldn't we move this discussion to dev@httpd? I think continuing this discussion here is somewhat pointless. Ah yes, I think I did see a reference to mod_load_average some time back when I was researching Apache throttling options, but I'd forgotten about it. Seems to be undocumented and not supported by its author, though. It's not featured with his other modules on http://www.outoforder.cc/, for instance. Sounds good to make this general-purpose for filters. Thanks for the pointer to mod_cache. It might be good to add a note about it to the mod_deflate documentation, as it wouldn't necessarily be obvious to people who aren't experts on Apache internals that it would cache output from mod_deflate so it wouldn't have to be recompressed next time. I was confused as to how caching would work with mod_deflate (without having a separate caching proxy instance) -- for instance, a lot of the stuff I read online (outside of httpd.apache.org) about it claimed it did its *own* caching, but I couldn't find any evidence of that in the documentation. Yes, good point about "instantaneous CPU usage", a la 'top', being a misnomer, since clearly it has to average over some time period to be meaningful -- it's just a shorter time period than with load averages, without any extra factors thrown in to the calculation, and expressed in terms of an easy to understand 0-100%, rather than load averages which can go arbitrarily high. And yeah, I hadn't really thought about this on Windows -- load averages would be even harder to understand for Windows jockeys. |