diff options
| -rw-r--r-- | faq/ram_limit.mdwn | 12 | ||||
| -rw-r--r-- | open_issues/64-bit_port.mdwn | 2 | ||||
| -rw-r--r-- | open_issues/gnumach_memory_management.mdwn | 16 |
3 files changed, 23 insertions, 7 deletions
diff --git a/faq/ram_limit.mdwn b/faq/ram_limit.mdwn index 5017925c..8e13f321 100644 --- a/faq/ram_limit.mdwn +++ b/faq/ram_limit.mdwn @@ -13,10 +13,14 @@ License|/fdl]]."]]"""]] [[!meta title="830 MiB RAM Limit"]] -Just like any 32-bit OS without bad tricks, GNU Mach can not cope well with lots -of memory. Latest versions of the Debian `gnumach` package will limit themselves -to around 1.7 GiB of memory. If you want more, you can twiddle the `VM_MAX_ADDRESS` -limit between kernelland and userland in `i386/include/mach/i386/vm_param.h`. +The 830MB RAM limit has been removed, but just like any 32-bit OS without bad tricks, +GNU Mach can not cope well with lots of memory. Latest versions of the Debian `gnumach` +package will limit themselves to 3 GiB of memory. If you want more, you can twiddle +the `VM_MAX_ADDRESS` limit between kernelland and userland in +`i386/include/mach/i386/vm_param.h`, but glibc and the hurd servers will not cope +well with less than 1 GB. + +There is a [[64-bit port|open_issues/64-bit_port]] in progress. If you have an older version, or still experience problems with `vmstat` (see above) reported much less memory than you have, the best is to limit the memory diff --git a/open_issues/64-bit_port.mdwn b/open_issues/64-bit_port.mdwn index 8658f1b7..656dd450 100644 --- a/open_issues/64-bit_port.mdwn +++ b/open_issues/64-bit_port.mdwn @@ -19,7 +19,7 @@ What is left for initial support (32-on-64) is * adding 64bit boot support from grub * implement 32/64 RPC compatibility for RPCs served by kernel. -See http://lists.gnu.org/archive/html/bug-hurd/2012-04/msg00000.html +See [[http://lists.gnu.org/archive/html/bug-hurd/2012-04/msg00000.html]] For pure 64bit support, we need to diff --git a/open_issues/gnumach_memory_management.mdwn b/open_issues/gnumach_memory_management.mdwn index 8eb0cf8a..911c2b51 100644 --- a/open_issues/gnumach_memory_management.mdwn +++ b/open_issues/gnumach_memory_management.mdwn @@ -11,8 +11,6 @@ License|/fdl]]."]]"""]] [[!tag open_issue_gnumach]] -There is a [[!FF_project 266]][[!tag bounty]] on this task. - [[!toc]] @@ -2389,3 +2387,17 @@ There is a [[!FF_project 266]][[!tag bounty]] on this task. <braunr> well, there is also a locking error in the slab allocator, although not a problem for a non preemptible kernel like gnumach <braunr> non preemptible / uniprocessor + +## IRC freenode, #hurd, 2016-12-29 + + <braunr> i've identified a fundamental flaw with the default pager + <braunr> and actually, with mach in general i suppose + <braunr> i assumed that it was necessary to trust the server only + <braunr> that a server didn't need to trust its client + <braunr> but mach messages carry memory that is potentially mapped from unprivileged pagers + <braunr> which means faulting on that memory effectively makes the faulting process a client to the unprivileged pager + <braunr> and that's something that can happen to the default pager during heavy memory pressure + <braunr> in which case it deadlocks on itself because the copyout hangs on a fault, waiting for the unprivileged pager to provide the data + <braunr> (which it can't because of heavy memory pressure and because it's unprivileged, it's blocked, waiting until allocations resume) + <braunr> the pageout daemon will keep paging out to the default pager in the hope those pages get freed + <braunr> but sending to the default pager is now impossible because its map is locked on the never-ending fault |