On Tue, Aug 17, 2010 at 10:09 AM, Tim Bird <[email protected]> wrote:
> I think we must be talking about different signatures. I'm referring
> to the one checked in frameworks/base/libs/utils/ZipFileRO.cpp,
> in ZipFileRO::parseZipArchive() about line 255 in the file:
>
> localHdr = basePtr + localHdrOffset;
> if (get4LE(localHdr) != kLFHSignature) {
> LOGW("Bad offset to local header: %d (at %d)\n",
> localHdrOffset, i);
> goto bail;
> }
>
Oh! Yes I was thinking about something completely different. This sounds
like a great optimization. :)
> Well, page faults are always inherently slower than reads, but you're right
> that
> they shouldn't be much slower. I'm still trying to figure out why reading
> the
> resource table (apparently) reads every byte of that portion of the
> archive, as opposed
> to only accessing the data sparsely, as you indicate is the intent.
>
It is going to depend a lot on the resources... all of the strings are in
one pool, so I could imagine they could be positioned there in such a way
that they are sparse in relation to what you need and cause a lot of page
faults.
Oh, another possibility -- the resource code tends to do a lot of validation
of the resource data at open time, so that when it retrieves things later it
doesn't need to repeatedly validate a bunch of stuff at each access. This
may be causing many pages to be touched.
--
Dianne Hackborn
Android framework engineer
[email protected]
Note: please don't send private questions to me, as I don't have time to
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