Messages in this thread | | | From | Nikita Danilov <> | Date | Tue, 1 Jul 2003 16:39:33 +0400 | Subject | Re: 2.5.73-mm2 |
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William Lee Irwin III writes: > On Tue, 1 Jul 2003, William Lee Irwin III wrote: > >> Well, I was mostly looking for getting handed back 0 when lowmem is > >> empty; I actually did realize they didn't give entirely accurate counts > >> of free lowmem pages. > > On Tue, Jul 01, 2003 at 12:08:03PM +0100, Hugh Dickins wrote: > > I'm not pleading for complete accuracy, but nr_free_buffer_pages() > > will never hand back 0 (if your system managed to boot). > > It's a static count of present_pages (adjusted), not of > > free pages. Or am I misreading nr_free_zone_pages()? > > You're right. Wow, that's even more worse than I suspected. >
Another thing is that if one boots with mem=X, nr_free_pagecache_pages() returns X. However part of X (occupied by kernel image, etc) is not part of any zone. As a result, zone actually contains fewer pages than reported by nr_free_pagecache_pages(). With X small enough (comparable with kernel image size, for example) this can confuse balance_dirty_pages() enough so that throttling would never start, and VM will oom_kill().
> > -- wli
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