diff options
Diffstat (limited to 'hurd/translator')
| -rw-r--r-- | hurd/translator/tmpfs.mdwn | 12 | ||||
| -rw-r--r-- | hurd/translator/tmpfs/discussion.mdwn | 17 | ||||
| -rw-r--r-- | hurd/translator/tmpfs/tmpfs_vs_defpager.mdwn | 121 |
3 files changed, 105 insertions, 45 deletions
diff --git a/hurd/translator/tmpfs.mdwn b/hurd/translator/tmpfs.mdwn index 0179ad6c..d1476a92 100644 --- a/hurd/translator/tmpfs.mdwn +++ b/hurd/translator/tmpfs.mdwn @@ -1,4 +1,4 @@ -[[!meta copyright="Copyright © 2007, 2008, 2009 Free Software Foundation, +[[!meta copyright="Copyright © 2007, 2008, 2009, 2011 Free Software Foundation, Inc."]] [[!meta license="""[[!toggle id="license" text="GFDL 1.2+"]][[!toggleable @@ -6,8 +6,8 @@ id="license" text="Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.2 or any later version published by the Free Software Foundation; with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts. A copy of the license -is included in the section entitled -[[GNU Free Documentation License|/fdl]]."]]"""]] +is included in the section entitled [[GNU Free Documentation +License|/fdl]]."]]"""]] `tmpfs` is a file system server for temporary data storage without using a real (permanent) [[backing_store]]. @@ -21,9 +21,3 @@ with the additional block-level indirection layer that `ext2` (or any other disk-based file system) imposes. However, `tmpfs` is not working correctly at the moment: - -[[!inline -pages="hurd/translator/tmpfs/*" -show=0 -feeds=no -actions=yes]] diff --git a/hurd/translator/tmpfs/discussion.mdwn b/hurd/translator/tmpfs/discussion.mdwn new file mode 100644 index 00000000..d7a08491 --- /dev/null +++ b/hurd/translator/tmpfs/discussion.mdwn @@ -0,0 +1,17 @@ +[[!meta copyright="Copyright © 2011 Free Software Foundation, Inc."]] + +[[!meta license="""[[!toggle id="license" text="GFDL 1.2+"]][[!toggleable +id="license" text="Permission is granted to copy, distribute and/or modify this +document under the terms of the GNU Free Documentation License, Version 1.2 or +any later version published by the Free Software Foundation; with no Invariant +Sections, no Front-Cover Texts, and no Back-Cover Texts. A copy of the license +is included in the section entitled [[GNU Free Documentation +License|/fdl]]."]]"""]] + +[[!tag open_issue_hurd]] + + * [[notes_bing]] + + * [[notes_various]] + + * [[tmpfs_vs_defpager]] diff --git a/hurd/translator/tmpfs/tmpfs_vs_defpager.mdwn b/hurd/translator/tmpfs/tmpfs_vs_defpager.mdwn index ef041a23..f0eb473c 100644 --- a/hurd/translator/tmpfs/tmpfs_vs_defpager.mdwn +++ b/hurd/translator/tmpfs/tmpfs_vs_defpager.mdwn @@ -1,4 +1,4 @@ -[[!meta copyright="Copyright © 2010 Free Software Foundation, Inc."]] +[[!meta copyright="Copyright © 2010, 2011 Free Software Foundation, Inc."]] [[!meta license="""[[!toggle id="license" text="GFDL 1.2+"]][[!toggleable id="license" text="Permission is granted to copy, distribute and/or modify this @@ -8,9 +8,12 @@ Sections, no Front-Cover Texts, and no Back-Cover Texts. A copy of the license is included in the section entitled [[GNU Free Documentation License|/fdl]]."]]"""]] +[[!tag open_issue_hurd]] + \#hurd, freenode, 2010 - <slpz> humm... why does tmpfs try to use the default pager? that's a bad idea, and probably will never work correctly... + <slpz> humm... why does tmpfs try to use the default pager? that's a bad + idea, and probably will never work correctly... * slpz is thinking about old issues <slpz> tmpfs should create its own pagers, just like ext2fs, storeio... <slpz> slopez@slp-hurd:~$ settrans -a tmp /hurd/tmpfs 10M @@ -21,53 +24,99 @@ License|/fdl]]."]]"""]] <slpz> :-) <pochu> slpz: woo you fixed it? <slpz> pochu: well, it's WIP, but reading/writing works... - <slpz> I've replaced the use of default pager for the standard pager creation mechanism - <antrik> slpz: err... how is it supposed to use swap space if not using the default pager? - <antrik> slpz: or do you mean that it should act as a proxy, just allocating anonymous memory (backed by the default pager) itself? - <youpi> antrik: the kernel uses the default pager if the application pager isn't responsive enough - <slpz> antrik: it will just create memory objects and provide zerofilled pages when requested by the kernel (after a page fault) - <antrik> youpi: that makes sense I guess... but how is that relevant to the question at hand?... + <slpz> I've replaced the use of default pager for the standard pager + creation mechanism + <antrik> slpz: err... how is it supposed to use swap space if not using the + default pager? + <antrik> slpz: or do you mean that it should act as a proxy, just + allocating anonymous memory (backed by the default pager) itself? + <youpi> antrik: the kernel uses the default pager if the application pager + isn't responsive enough + <slpz> antrik: it will just create memory objects and provide zerofilled + pages when requested by the kernel (after a page fault) + <antrik> youpi: that makes sense I guess... but how is that relevant to the + question at hand?... <slpz> antrik: memory objects will contain the data by themselves - <slpz> antrik: as youpi said, when memory is scarce, GNU Mach will start paging out data from memory objects to the default pager + <slpz> antrik: as youpi said, when memory is scarce, GNU Mach will start + paging out data from memory objects to the default pager <slpz> antrik: that's the way in which pages will get into swap space <slpz> (if needed) - <youpi> the thing being that the tmpfs pager has a chance to select pages he doesn't care any more about - <antrik> slpz: well, the point is that instead of writing the pages to a backing store, tmpfs will just keep them in anonymous memory, and let the default pager write them out when there is pressure, right? - <antrik> youpi: no idea what you are talking about. apparently I still don't really understand this stuff :-( + <youpi> the thing being that the tmpfs pager has a chance to select pages + he doesn't care any more about + <antrik> slpz: well, the point is that instead of writing the pages to a + backing store, tmpfs will just keep them in anonymous memory, and let the + default pager write them out when there is pressure, right? + <antrik> youpi: no idea what you are talking about. apparently I still + don't really understand this stuff :-( <youpi> ah, but tmpfs doesn't have pages he doesn't care about, does it? - <slpz> antrik: yes, but the term "anonymous memory" could be a bit confusing. - <slpz> antrik: in GNU Mach, anonymous memory is backed by a memory object without a pager. In tmpfs, nodes will be allocated in memory objects, and the pager for those memory objects will be tmpfs itself - <antrik> slpz: hm... I thought anynymous memory is backed by memory objects created from the default pager? - <antrik> yes, I understand that tmpfs is supposed to be the pager for the objects it provides. they are obviously not anonymoust -- they have inodes in the tmpfs name space - <antrik> but my understanding so far was that when Mach returns pages to the pager, they end up in anonymous memory allocated to the pager process; and then this pager is responsible for writing them back to the actual backing store + <slpz> antrik: yes, but the term "anonymous memory" could be a bit + confusing. + <slpz> antrik: in GNU Mach, anonymous memory is backed by a memory object + without a pager. In tmpfs, nodes will be allocated in memory objects, and + the pager for those memory objects will be tmpfs itself + <antrik> slpz: hm... I thought anynymous memory is backed by memory objects + created from the default pager? + <antrik> yes, I understand that tmpfs is supposed to be the pager for the + objects it provides. they are obviously not anonymoust -- they have + inodes in the tmpfs name space + <antrik> but my understanding so far was that when Mach returns pages to + the pager, they end up in anonymous memory allocated to the pager + process; and then this pager is responsible for writing them back to the + actual backing store <antrik> am I totally off there?... - <antrik> (i.e. in my understanding the returned pages do not reside in the actual memory object the pager provides, but in an anonymous memory object) - <slpz> antrik: you're right. The trick here is, when does Mach return the pages? - <slpz> antrik: if we set the attribute "can_persist" in a memory object, Mach will keep it until object cache is full or memory is scarce + <antrik> (i.e. in my understanding the returned pages do not reside in the + actual memory object the pager provides, but in an anonymous memory + object) + <slpz> antrik: you're right. The trick here is, when does Mach return the + pages? + <slpz> antrik: if we set the attribute "can_persist" in a memory object, + Mach will keep it until object cache is full or memory is scarce <slpz> or we change the attributes so it can no longer persist, of course - <slpz> without a backing store, if Mach starts sending us pages to be written, we're in trouble - <slpz> so we must do something about it. One option, could be creating another pager and copying the contents between objects. + <slpz> without a backing store, if Mach starts sending us pages to be + written, we're in trouble + <slpz> so we must do something about it. One option, could be creating + another pager and copying the contents between objects. <antrik> another pager? not sure what you mean - <antrik> BTW, you didn't really say why we can't use the default pager for tmpfs objects :-) - <slpz> well, there're two problems when using the default pager as backing store for translators - <slpz> 1) Mach relies on it to do swapping tasks, so meddling with it is not a good idea - <slpz> 2) There're problems with seqnos when trying to work with the default pager from tasks other the kernel itself + <antrik> BTW, you didn't really say why we can't use the default pager for + tmpfs objects :-) + <slpz> well, there're two problems when using the default pager as backing + store for translators + <slpz> 1) Mach relies on it to do swapping tasks, so meddling with it is + not a good idea + <slpz> 2) There're problems with seqnos when trying to work with the + default pager from tasks other the kernel itself <slpz> (probably, the latter could be fixed) - <slpz> antrik: pager's terminology is a bit confusing. One can also say creating another memory object (though the function in libpager is "pager_create") + <slpz> antrik: pager's terminology is a bit confusing. One can also say + creating another memory object (though the function in libpager is + "pager_create") <antrik> not sure why "meddling" with it would be a problem... - <antrik> and yeah, I was vaguely aware that there is some seqno problem with tmpfs... though so far I didn't really understand what it was about :-) + <antrik> and yeah, I was vaguely aware that there is some seqno problem + with tmpfs... though so far I didn't really understand what it was about + :-) <antrik> makes sense now - <antrik> anyways, AIUI now you are trying to come up with a mechanism where the default pager is not used for tmpfs objects directly, but without making it inefficient? - <antrik> slpz: still don't understand what you mean by creating another memory object/pager... + <antrik> anyways, AIUI now you are trying to come up with a mechanism where + the default pager is not used for tmpfs objects directly, but without + making it inefficient? + <antrik> slpz: still don't understand what you mean by creating another + memory object/pager... <antrik> (and yeat, the terminology is pretty mixed up even in Mach itself) - <slpz> antrik: I meant creating another pager, in terms of calling again to libpager's pager_create - <antrik> slpz: well, I understand what "create another pager" means... I just don't understand what this other pager would be, when you would create it, and what for... + <slpz> antrik: I meant creating another pager, in terms of calling again to + libpager's pager_create + <antrik> slpz: well, I understand what "create another pager" means... I + just don't understand what this other pager would be, when you would + create it, and what for... <slpz> antrik: oh, ok, sorry - <slpz> antrik: creating another pager it's just a trick to avoid losing information when Mach's objects cache is full, and it decides to purge one of our objects - <slpz> anyway, IMHO object caching mechanism is obsolete and should be replaced + <slpz> antrik: creating another pager it's just a trick to avoid losing + information when Mach's objects cache is full, and it decides to purge + one of our objects + <slpz> anyway, IMHO object caching mechanism is obsolete and should be + replaced <slpz> I'm writting a comment to bug #28730 which says something about this <slpz> antrik: just one more thing :-) - <slpz> if you look at the code, for most time of their lives, anonymous memory objects don't have a pager + <slpz> if you look at the code, for most time of their lives, anonymous + memory objects don't have a pager <slpz> not even the default one - <slpz> only the pageout thread, when the system is running really low on memory, gives them a reference to the default pager by calling vm_object_pager_create + <slpz> only the pageout thread, when the system is running really low on + memory, gives them a reference to the default pager by calling + vm_object_pager_create <slpz> this is not really important, but worth noting ;-) |