On 24-Nov-13, at 11:41 PM, Mike Frysinger wrote:
On Wednesday 20 November 2013 17:07:42 Helge Deller wrote:
locale-gen from glibc showed a strange problem on parisc:
pedantic: locale-gen is from distros while glibc itself provides
localedef.
mmap2(NULL, 536870912, PROT_NONE, MAP_SHARED, 3, 0) = 0x42a54000
mmap2(0x42a54000, 103860, PROT_READ|PROT_WRITE, MAP_SHARED|
MAP_FIXED, 3, 0)
= -1 EINVAL (Invalid argument)
Basically it was just trying to re-mmap() a file at the same address
which it was given by a previous mmap() call. But this remapping
failed
with EINVAL.
The problem is, that when MAP_FIXED and MAP_SHARED flags were used,
we
didn't included the mapping-based offset when we verified the
alignment of
the given fixed address against the offset which we calculated it
in the
previous call.
hmm, which version of glibc were you trying ? we landed this change
recently:
https://sourceware.org/git/?p=glibc.git;a=commitdiff_plain;h=17db6e8d6b12f55e312fcab46faf5d332c806fb6
it's part of glibc-2.18. we know earlier versions of localedef
failed on
systems like parisc, although it seemed to really only creep up on
64bit
kernels reliably.
Besides the above, our mmap allocater doesn't work well when we have a
large number
of small allocations:
https://rt.perl.org:443/rt3/Ticket/Display.html?id=119567
Effectively, we allocate 4 MB per locale and soon run out of memory.
Problem is here:
/*
* We need to know the offset to use. Old scheme was to look for
* existing mapping and use the same offset. New scheme is to use the
* address of the kernel data structure as the seed for the offset.
* We'll see how that works...
*
* The mapping is cacheline aligned, so there's no information in the
bottom
* few bits of the address. We're looking for 10 bits (4MB / 4k), so
let's
* drop the bottom 8 bits and use bits 8-17.
*/
static int get_offset(struct address_space *mapping)
{
return (unsigned long) mapping >> 8;
}
We rarely suceed in allocating two or more maps in the same 4 MB block
of memory.
Dave
--
John David Anglin dave.anglin@xxxxxxxx
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