On 05/03/2011 12:35 PM, David Lehman wrote:
> New minimum for physical memory is 640MB. New minimum memory for us to
> not require swap space is 1152MB. I arrived at this number by doing an
> x86_64 install of F15 Beta in kvm, using "Web Server" package set. I
> tried 1024MB and it froze during selinux-policy-targeted installation.
I have no doubt that is what you observed. However, an installer which
requires more than 1GB of system RAM is unreasonable, even if there is
no swap space. That is too much RAM. Something fundamental is broken.
One guess for needing so much RAM is that the installer's allocator
(python/C memory manager) never reclaims anything unless forced.
The amount of memory _apparently_ required increases package-by-package.
When the %post sub-process for selinux-policy-targeted is invoked,
then inside the installer there is lots of space that is free (or
_could_ be free), so there would be no problem if swap space were
available, or if reclaiming had been done. But because swap space
is not available and reclaiming has not yet been necessary,
then there is not enough RAM for both the never-reclaimed installer
and the %post sub-process.
SUGGESTIONS: See if disaster can be avoided by forcing the installer's
memory manager to run in less total space. How? Several things to try:
1. Invoke garbage collection explicitly every 10 packages.
2. Limit the installer's data size to 350MB with the shell builtin
"ulimit -d 350000", or limit the total virtual size using
"ulimit -v 350000".
3. Limit the installer address space by using the C code
setrlimit(RLIMIT_AS, &{350000*1024, 350000*1024});
4. Check if the installer's class structure for a package,
or the installer's use of it, causes unintended retention of I/O or
decompression buffers that are not shared with other packages.
(Did some destructor not get called? Is a big object retained
on a list when it would suffice to keep only the string name
of the package? Etc.)
5. Ask the maintainers of selinux-policy-targeted to check for
over-estimating (and then over-allocating) runtime space requirements,
particularly with regard to swap space being unavailable.
If none of those ideas work, then here is the most-powerful hammer:
6. Surround the install of each package with:
child = fork();
if (-1==child) /* fork() failed */
try_again;
else if (child) /* in parent */
wait_for(child);
else { /* in child */
install_package();
exit(status);
}
This guarantees that the installation of a package does not change the
state of the allocator arena in the parent. My hypothesis is: the largest
amount of RAM required by the installer will be not more than the RAM
required after only the first few packages have been installed:
about 280MB or so. [Obviously this idea can be applied to each step
before package installation, too. All the GUI dialogs
shouldn't increase the process size very much, either.]
--
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