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Diffstat (limited to 'microkernel/mach/memory_object/discussion.mdwn')
| -rw-r--r-- | microkernel/mach/memory_object/discussion.mdwn | 43 |
1 files changed, 42 insertions, 1 deletions
diff --git a/microkernel/mach/memory_object/discussion.mdwn b/microkernel/mach/memory_object/discussion.mdwn index a006429b..c874b255 100644 --- a/microkernel/mach/memory_object/discussion.mdwn +++ b/microkernel/mach/memory_object/discussion.mdwn @@ -10,7 +10,7 @@ License|/fdl]]."]]"""]] [[!tag open_issue_documentation open_issue_gnumach]] -IRC, freenode, #hurd, 2011-08-05 +IRC, freenode, #hurd, 2011-08-05: < neal> braunr: For instance, memory objects are great as they allow you to specify the mapping policy in user space. @@ -22,3 +22,44 @@ IRC, freenode, #hurd, 2011-08-05 < neal> I'm not sure what you mean by page cache lru appoximateion < braunr> the kernel eviction policy :) < neal> that's an implementation detail + +IRC, freenode, #hurd, 2011-09-05: + + <braunr> mach isn't a true modern microkernel, it handles a lot of + resources, such as high level virtual memory and cpu time + <braunr> for example, the page replacement mechanism can't be implemented + outside the kernel + <braunr> yet, it provides nothing to userspace server to easily allocate + resources on behalf of clients + <braunr> so, when a thread calls an RPC, the cpu time used to run that RPC + is accounted on the server task + <braunr> the hurd uses lots of external memory managers + +[[external_pager_mechanism]]. + + <braunr> but they can't decide how to interact with the page cache + <braunr> the kernel handles the page cache, and initiates the requests to + the pagers + <cjuner> braunr, why can't they decide that? + <braunr> because it's implemented in the kernel + <braunr> and there is nothing provided by mach to do that some other way + <slpz_> braunr: you probably already know this, but the problem with client + requests being accounted on behalf the server, is fixed in Mach with + Migrating Threads + +[[open_issues/mach_migrating_threads]]. + + <braunr> slpz_: migrating threads only fix the issue for the resources + managed by mach, not the external servers + <braunr> slpz_: but it's a (imo necessary) step to completely solve the + issue + <braunr> in addition to being a great feature for performance (lighter + context switchers, less state to track) + <braunr> it also helps priority inversion problems + <slpz_> braunr: I was referring just to cpu-time, but I agree with you an + interface change is needed for external pagers + <braunr> slpz_: servers in general, not necessarily pagers + <slpz_> as a way to mitigate the effect of Mach paging out to external + pagers, the folks at OSF implemented an "advisory pageout", so servers + are "warned" that they should start paging out, and can decide which + pages are going to be flushed by themselves |