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strict-overcommit : Strict VM overcommit accounting
This patch adds strict VM overcommit accounting to the mainline 2.4
kernel, thus allowing overcommit to be truly disabled. This feature
has been in 2.4-ac, Red Hat Enterprise Linux 3 (RHEL 3) vendor kernels,
and 2.6 for a long while.
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| Initial date: | 2005/12/29 |
| Description: | Strict VM overcommit accounting |
| Author(s): | Barry K.Nathan |
| Conflicts with: | pax, grsecurity |
| See also: | oc+pax |
| Abstract: | This patch adds strict VM overcommit accounting to the mainline 2.4
kernel, thus allowing overcommit to be truly disabled. This feature
has been in 2.4-ac, Red Hat Enterprise Linux 3 (RHEL 3) vendor kernels,
and 2.6 for a long while.
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Notes
Most of the code was merged from 2.4.27-pre2-pac1, as well as a hunk
from 2.4.22-ac4 for fs/exec.c that was missing from the -pac kernels.
(Without that, the patch was seriously broken.) I also added a
fork-related accounting fix from the RHEL 3 kernel -- it turns out that
the exact same fix is also present in 2.6. Finally, I backported changes
to move_vma() from 2.6, so that do_munmap() does not need a 4th argument;
this avoids disrupting arch and driver code.
This patch is against 2.4.33-pre1, although it applies to 2.4.32 as well,
and that is where I did most of my testing. I'm hoping that it's not too
late to add this to mainline 2.4, although I realize that it might be.
Known problems/quirks of this patch:
- The documentation (from -pac) mentions an overcommit mode 3, which does
not appear to actually exist (as far as I can tell). This can be fixed
in a future patch, and I'll probably do that soon.
- Like -ac/-pac, but unlike RHEL 3 or mainline 2.6, this patch does not
add Committed_AS to /proc/meminfo. IMO it's an insanely useful bit of
information to have, so I'll have another patch very soon to add this.
Signed-off-by: Barry K. Nathan
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Contents
- Strict VM overcommit accounting for 2.4.32/2.4.33-pre1 - Barry K.Nathan - 2005/12/29
This patch adds strict VM overcommit accounting to the mainline 2.4
kernel, thus allowing overcommit to be truly disabled. This feature
has been in 2.4-ac, Red Hat Enterprise Linux 3 (RHEL 3) vendor kernels,
and 2.6 for a long while.
Local link : 2.4.33-pre1-strict-overcommit-1
- add CommitLimit, Committed_AS to 2.4 strict VM overcommit - Barry K.Nathan - 2005/12/29
This patch adds two more lines of output to /proc/meminfo, CommitLimit
and Committed_AS. On a system running the strict VM overcommit patch,
these are useful bits of information (especially Committed_AS, which
lets you know how close you are to full committment).
Local link : 2.4.33-pre1-overcommit-stats-1
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(C) Willy Tarreau - 2008-06-01