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From "William A. Rowe, Jr." <wr...@covalent.net>
Subject Re: apr_buckets_file.c:file_read + XTHREAD
Date Wed, 28 Nov 2001 05:55:57 GMT
From: "Cliff Woolley" <cliffwoolley@yahoo.com>
Sent: Tuesday, November 27, 2001 11:39 PM

> On Tue, 27 Nov 2001, Ryan Bloom wrote:
> > Bill's idea was to map and then unmap the individual sections of the
> > file, so that no more than one section was mapped at a time.  

No, properly I implied that we have no more sections mapped than we are
actually interested in, at any given time.

> > If you
> > do that, and you really unmap each section as you map the next, you
> > will be thrashing your MMAPs.  

How?  See my other post on why unmapping/remapping is really painless
when weighed against reading, and pagefaulting.

> > If you are really going to leave each
> > section as an MMAP, then I would agree completely, and say let's do
> > it, but that wasn't what Bill suggested.
> It might not be exactly what he said, but I thought it's what he _meant_.
> Ahh, don't you love the expressiveness of email?  :-)  One at a time is
> typically what you get with the code I posted anyhow since most filters
> limit how much they'll buffer, but the one-at-a-time rule is just not
> enforced.  If it were enforced, then oh yeah, that would be bad.  :)

No, I really implied that we do unmap those that are consumed.  If a really
bad filter reads in all 200 buckets of 4MB each, then the system will start
flailing.  But no filter author would create such a design, no :-?

If you read from the bucket (mmap) and pass it on, the memory footprint
won't get out of hand.


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