Messages in this thread | | | Date | Sat, 27 Dec 2003 15:55:38 -0800 | From | William Lee Irwin III <> | Subject | Re: Page aging broken in 2.6 |
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On Sun, Dec 28, 2003 at 12:07:58AM +0100, Roger Luethi wrote: > It can matter. Evicting a page that is infrequently referenced by many > processes increases the chance that all runnable processes block waiting > for that same page later. The likelihood of that happening grows under > memory pressure, when "infrequently" may actually be "quite often" and > when disk I/O is congested (resulting in higher disk access times). > You won't have the same effect when evicting a page that is referenced > by one process only, no matter how frequently.
Part of this is unrealistic; paging I/O being congested must be due to paging itself causing seeks without additional I/O load. Reading a single page once and then faulting that one page back into numerous process address spaces is only one I/O request, and so cannot seek in and of itself. So in this scenario, a convoy of processes on a single page is plausible; aggravated paging I/O seekiness is not. Did you have in mind some additional I/O load? Or do affected processes actually all fault before the one I/O completes, and so all block temporarily?
On Sun, Dec 28, 2003 at 12:07:58AM +0100, Roger Luethi wrote: > Having all processes blocked is indeed one problem of 2.6 under memory > pressure. I don't know what the cause is, though.
Can you capture sysrq t while a situation like this is in progress?
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