Messages in this thread | | | Date | Mon, 18 Feb 2002 02:38:00 +0100 | From | Andrea Arcangeli <> | Subject | Re: [TEST] page tables filling non-highmem |
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On Fri, Feb 15, 2002 at 09:59:45AM +0100, Daniel Phillips wrote: > On February 15, 2002 05:51 am, William Lee Irwin III wrote: > > The following testcase brought down 2.4.17 mainline on an > > 8-way P-III 700MHz machine with 12GB of RAM. The last thing > > logged from it was a LowFree of 2MB with 9GB of highmem free > > after something like 6-8 hours of pounding away, at which > > time the machine stopped responding (IIRC it was given ~12 > > hours to echo another character). > > > > This testcase is a blatant attempt to fill the direct-mapped > > portion of the kernel virtual address space with process pagetables. > > It was suspected such a thing was happening in another failure scenario > > which is what motivated me to devise this testcase. I believe a fix > > already exists (i.e. aa's ptes in highmem stuff) though I've not yet > > verified its correct operation here. > > As you described it to me on irc, this demonstration turns up a > considerably worse problem than just having insufficient space for > page tables - the system locks up hard instead of doing anything > reasonable on page table-related oom. It's wrong that the system > should behave this way, it is after all, just an oom. > > Now that basic stability issues seem to be under control, perhaps > it's time to give the oom problem the attention it deserves?
My tree doesn't lock up hard even without pte-highmem applied. The task gets killed. backout pte-highmem, try the same testcase again on my tree and you'll see. The oom handling in mainline is deadlock prone, I always known this and that's why I always rejected it. Nobody but me acklowledged this problem and I spent quite an amount of time convincing mainline maintainers about those deadlock flaws of the mainline approch but I failed so I giveup waiting for a report like this, just like with all the other stuff that is now in my vm patch, 90% of it I tried to push it separately into mainline before having to accumulate it.
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