Rasmus Lerdorf wrote:
>>>>Perhaps automatic detection could be option? if (filesize > X)
>>>>blockread else mmap? It seems like the most intuitive way to implement
>>>>it...
>>>>
>>>>
>>>Sounds a bit magical. Why not just a block_readfile() function?
>>>
>>
>>Mainly the bloat factor, we already have a large core, imho, functions
>>shouldn't be added unless there are no workarounds. Also, it requires a
>>little too much thought, into what sizes are good for mmap() and what
>>sizes are good for block read's (it also requires knowledge of mmap(),
>>because many people might automatically assume that block_read would
>>always be faster). I'm pretty sure if we polled php-general and php-qa
>>(the more "knowledgable" user bases), most people wouldn't really
>>understand what mmap does, or what it is for or when it is beneficial to
>>use it.
>>
>>As for magical, well a bit, but good magic and internal magic (not
>>syntactical magic). I'd assume that most systems have a certain point
>>where mmap is no longer more beneficial than reading a file by chunks.
>>If we can find a reasonable number (or have a user specify that in a
>>configuration option if really necessary), it saves the user the trouble
>>of thinking about something which is pretty low-level and it reduces
>>bloat. I don't really see a downside to this magic.
>>
>
> But, the issue here isn't one of which is faster. The issue here is one
> of memory usage. If you have a 600M iso image that you decide to
> readfile() for a download page of some sort, then you are going to end up
> with a 600M httpd process. And soon you will have lots of those as more
> people hit the page.
>
>
> So to be truely magical here, PHP would have to check the amount of spare
> RAM on the system, divide that by MaxClients and set that as the largest
> filesize to mmap() because anything larger could result in the box going
> into swap.
>
point taken :)
> I obviously don't think such a check is feasible. The only real question
> here is whether to add a user configurable max-mmap setting or to add a
> second function that never mmaps.
>
+1 for the configuration option.
-Sterling
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