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+[[!meta copyright="Copyright © 2011, 2012 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]]
+
+[[!toc]]
+
+
+# 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
+
+
+# [[gnumach_page_cache_policy]]