On Thu, May 17, 2001 at 11:10:57PM -0700, 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.
mmap will not increase the size of your process as it doesn't
call sbrk().
>
> 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.
>
> 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.
question is: do we really need this mmap stuff at all?
with readfile we should easyly be able to saturate a
pipe of any size using just read and write.
tc
>
> -Rasmus
>
>
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