On 07/08/15 at 05:46P, Alan Cox wrote: > Author: alc > Date: Wed Jul 8 17:45:59 2015 > New Revision: 285282 > URL: https://svnweb.freebsd.org/changeset/base/285282 > > Log: > The intention of r254304 was to scan the active queue continuously. > However, I've observed the active queue scan stopping when there are > frequent free page shortages and the inactive queue is steadily refilled > by other mechanisms, such as the sequential access heuristic in vm_fault() > or madvise(2).
What would be the actual downside/effect of this scenario? i.e. What goes wrong when active queue scan stops and what would I see/observe on a system when the problem is going on - is what I want to understand. > To remedy this problem, record the time of the last active > queue scan, and always scan a number of pages proportional to the time > since the last scan, regardless of whether that last scan was a > timeout-triggered ("pass == 0") or free-page-shortage-triggered ("pass > > 0") scan. > > Also, on a timeout-triggered scan, allow a full scan of the active queue > when the system is short of inactive pages. > > Reviewed by: kib > MFC after: 6 weeks > Sponsored by: EMC / Isilon Storage Division [skip] Thanks in advance. Cheers, Hiren
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