Date: Fri, 30 Apr 2004 10:42:33 -0400 (EDT) From: Andrew Gallatin <gallatin@cs.duke.edu> To: Marcel Moolenaar <marcel@xcllnt.net> Cc: freebsd-emulation@freebsd.org Subject: Re: user mode linux? Message-ID: <16530.26073.555667.482789@grasshopper.cs.duke.edu> In-Reply-To: <20040430000437.GB39055@ns1.xcllnt.net> References: <16528.65255.326986.106534@grasshopper.cs.duke.edu> <20040430000437.GB39055@ns1.xcllnt.net>
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Marcel Moolenaar writes:
>
> Two things you might wan to look into:
> 1. Is there an issue with mmap(2)'ing sparse files?
> 2. Are limits being hit (most notably RLIMIT_DATA)?
>
I think I've "figured it out" to the extent I can.
The mmap is done like this:
linux_mmap_common(0, 1785856, 3, 0x00000801, 3, 0x0)
The failure happens due to this check in vm_map_findspace():
if (start > map->max_offset)
When I print things out here, I see:
start = 0xc0001000, map->min_offset = 0x0, map->max_offset = 0xbfc00000
This "start" is the addr that was chosen in mmap() for non-MAP_FIXED
mappings:
if (addr == 0 ||
(addr >= round_page((vm_offset_t)vms->vm_taddr) &&
addr < round_page((vm_offset_t)vms->vm_daddr +
lim_max(td->td_proc, RLIMIT_DATA))))
addr = round_page((vm_offset_t)vms->vm_daddr +
lim_max(td->td_proc, RLIMIT_DATA));
I can work around this with a hack in linux_mmap_common() to set the
address to 4K so that this code never runs, but I'd really like to
understand what's happening...
Hmm.. Another work around is to break into ddb and *reduce* maxdsize
from the default 512MB to 256MB:
db> e maxdsiz
maxdsiz: 20000000
db> w maxdsiz 10000000
Thanks,
Drew
Index: i386/linux/linux_machdep.c
===================================================================
RCS file: /home/ncvs/src/sys/i386/linux/linux_machdep.c,v
retrieving revision 1.41
diff -u -r1.41 linux_machdep.c
--- i386/linux/linux_machdep.c 4 Feb 2004 21:52:54 -0000 1.41
+++ i386/linux/linux_machdep.c 30 Apr 2004 14:19:21 -0000
@@ -539,6 +539,9 @@
(void *)bsd_args.addr, bsd_args.len, bsd_args.prot,
bsd_args.flags, bsd_args.fd, (int)bsd_args.pos);
#endif
+ if (((bsd_args.flags & MAP_FIXED) == 0) && (bsd_args.addr == 0))
+ bsd_args.addr = 4096;
+
error = mmap(td, &bsd_args);
#ifdef DEBUG
if (ldebug(mmap))
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