Messages in this thread | | | Date | Sun, 9 Mar 2008 12:56:11 +0100 (CET) | From | Thomas Gleixner <> | Subject | Re: quicklists confuse meminfo |
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On Sun, 9 Mar 2008, Ingo Molnar wrote:
> > * Thomas Gleixner <tglx@linutronix.de> wrote: > > > Bart reported http://bugzilla.kernel.org/show_bug.cgi?id=9991. He > > assumed a memory leak in 32bit kernels when he analyzed the output of > > /proc/meminfo. > > > > The leak is not a leak, it's an accounting bug. quicklists keep a > > large amount of pages which are accounted as used memory. > [...] > > Another strange observation about quicklists is the imbalance of the > > quicklists across CPUs. Running the above loop on a 2way machine I can > > observe that the quicklist pages are acuumulating on one CPU. Stopping > > and restarting the loop a couple of times can shift the accumulation > > from one to the other CPU. > > hm. I think we should not let this much RAM hang around in a > special-purpose allocator like quicklists. Shouldnt the quicklists be > temporary in nature, and be trimmed much more agressively? > > in fact, we have a check_pgt_cache() call in cpu_idle(), which does: > > quicklist_trim(0, pgd_dtor, 25, 16); > > but it appears we dont do quicklist trimming anywhere else! So if a > system has no idle time, the quicklist can grow unbounded, and that's a > real memory leak IMO.
Right, also the quicklist_trim() in idle() is freeing at max 16 pages in one go. According to the quicklist_trim() code we keep up to (node_free_pages / 16) in the quicklist unconditionally, which seems rather odd as well.
Thanks, tglx
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