| Title | MPS on OS X needs a protection module in order to be faster |
| Status | closed |
| Priority | essential |
| Assigned user | David Jones |
| Organization | Ravenbrook |
| Description | The MPS on OS X is slow. In particular it is much slower than a stop-and-copy collector. See [1], RB's experiments with sc (Implemented on PowerPC OS X) Now required on Intel OS X. |
| Analysis | One of the reasons it is slow is that OS X has no protection module (protxc). We need to implement a protection module in order to remove this cause of slowness. We could probably use protfr.c unmodified, or modified very little. So far, 2005-03-04 it seems that whilst the mprotect code works more or less as is, the signal handling seems screwed. Tests seem to go into an infinite loop and when running under a debugger it doesn't seem possible to handle the signal properly or break into the signal handler, and so is impossible to debug. Looking at the Boehm GC code (this is very unpleasant) suggests that they use Mach vm_protect and exception handling. Not only is this cool, it just might work. [2] (a post by Timothy Wood of Omnigroup) seems incredibly useful; I find by looking at the Boehm GC code. Aha, it turns out that si_addr is the address of the faulting instruction, and the faulting address is someplace else. Thanks to NB for some snorkelling help. Now proceeding with traditional UNIX mprotect / sigaction handler. Which seems to work just fine. 2007-02-20 DRJ: Need to implement on Intel OS X. Probably using some combination of protxcpp.c, protfri3.c, and protso.c 2007-03-02 DRJ: On Intel OS X the info->si_addr field is correct, so we can use code which looks much like proto1.c (which is slightly cleaner than protso.c). 2007-03-09 DRJ: Implemented in protix.c for Intel Darwin. |
| How found | manual_test |
| Evidence | [1] //info.ravenbrook.com/mail/2005/03/01/11-16-25/0.txt[2] http://www.omnigroup.com/mailman/archive/macosx-dev/2000-June/002030.html |
| Observed in | 1.105.0 |
| Created by | David Jones |
| Created on | 2005-03-02 09:51:10 |
| Last modified by | David Jones |
| Last modified on | 2007-03-09 11:26:10 |
| History | 2005-03-02 DRJ Created 2005-03-04 DRJ Updated 2007-02-20 DRJ Required for Intel now. 2007-03-02 DRJ MacTel notes. 2007-03-09 DRJ Closed |
| Change | Effect | Date | User | Description |
|---|---|---|---|---|
| 161905 | closed | 2007-03-09 09:35:31 | David Jones | MPS: Typo in config.h was breaking FreeBSD builds. |
| 161902 | open | 2007-03-08 21:50:28 | David Jones | MPS: Protection for Intel Darwin. Hopefully cross-platform. |
| 147633 | open | 2005-03-04 15:53:57 | David Jones | MPS: Removing some pretty useful printf debugging code from protxcpp |
| 147632 | open | 2005-03-04 15:53:00 | David Jones | MPS: oops. previous submit blatted over my dirty branch. must have forgotten to p4 edit it. |
| 147629 | open | 2005-03-04 15:37:12 | David Jones | MPS: implemented prot on OS X. |