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+[[!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_gnumach]]
+
+IRC, freenode, #hurd, 2011-11-28:
+
+ <braunr> youpi: would you find it reasonable to completely disable the page
+ cache in gnumach ?
+ <braunr> i'm wondering if it wouldn't help make the system more stable
+ under memory pressure
+ <youpi> assuming cache=writeback in gnumach?
+ <youpi> because disabling the page cache will horribly hit performance
+ <braunr> no, it doesn't have anything to do with the host
+ <braunr> i'm not so sure
+ <braunr> while observing the slab allocator, i noticed our page cache is
+ not used that often
+ <youpi> eeh?
+ <youpi> apart from the damn 4000 limitation, I've seen it used
+ <youpi> (and I don't why it wouldn't be used)
+ <youpi> (e.g. for all parts of libc)
+ <youpi> ah, no, libc would be kept open by ext2fs
+ <braunr> taht's precisely because of the 4k limit
+ <youpi> but e.g. .o file emitted during make
+ <braunr> well, no
+ <youpi> well, see the summary I had posted some time ago, the 4k limit
+ makes it completely randomized
+ <youpi> and thus you lose locality
+ <braunr> yes
+ <youpi> but dropping the limit would just fix it
+ <braunr> that's my point
+ <youpi> which I had tried to do, and there were issues, you mentioned why
+ <youpi> and (as usual), I haven't had anyu time to have a look at the issue
+ again
+ <braunr> i'm just trying to figure out the pros and cons for having teh
+ current page cache implementation
+ <braunr> but are you saying you tried with a strict limit of 0 ?
+ <youpi> non, I'm saying I tried with no limit
+ <youpi> but then memory fills up
+ <braunr> yes
+ <youpi> so trying to garbage collect
+ <braunr> i tried that too, the system became unstable very quickly
+ <youpi> but refs don't falldown to 0, you said
+ <braunr> did i ?
+ <youpi> or maybe somebody else
+ <youpi> see the list archives
+ <braunr> that's possible
+ <braunr> i'd imagine someone like sergio lopez
+ <youpi> possibly
+ <youpi> somebody that knows memory stuff way better than me in any case
+ <braunr> youpi: i'm just wondering how much we'd loose by disabling the
+ page cache, and if we actually gain more stability (and ofc, if it's
+ worth it)
+ <youpi> no idea, measures will tell
+ <youpi> fixing the page cache shouldn't be too hard I believe, however
+ <youpi> you just need to know what you are doing, which I don't
+ <youpi> I do believe the cache is still at least a bit useful
+ <youpi> even if dumb because of randomness
+ <youpi> e.g. running make lib in the glibc tree gets faster on second time
+ <youpi> because the cache wouldbe filled at least randomly with glibc tree
+ stuff
+ <braunr> yes, i agree on that
+ <youpi> braunr: btw, the current stability is fine for the buildds
+ <youpi> restarting them every few days is ok
+ <youpi> so I'd rather keep the performance :)
+ <braunr> ok