Matthew Dillon faa273d5c2 Rip out PQ_ZERO queue. PQ_ZERO functionality is now combined in with ... PQ_FREE. There is little operational difference other then the kernel being a few kilobytes smaller and the code being more readable. * vm_page_select_free() has been *greatly* simplified. * The PQ_ZERO page queue and supporting structures have been removed * vm_page_zero_idle() revamped (see below) PG_ZERO setting and clearing has been migrated from vm_page_alloc() to vm_page_free[_zero]() and will eventually be guarenteed to remain tracked throughout a page's life ( if it isn't already ). When a page is freed, PG_ZERO pages are appended to the appropriate tailq in the PQ_FREE queue while non-PG_ZERO pages are prepended. When locating a new free page, PG_ZERO selection operates from within vm_page_list_find() ( get page from end of queue instead of beginning of queue ) and then only occurs in the nominal critical path case. If the nominal case misses, both normal and zero-page allocation devolves into the same _vm_page_list_find() select code without any specific zero-page optimizations. Additionally, vm_page_zero_idle() has been revamped. Hysteresis has been added and zero-page tracking adjusted to conform with the other changes. Currently hysteresis is set at 1/3 (lo) and 1/2 (hi) the number of free pages. We may wish to increase both parameters as time permits. The hysteresis is designed to avoid silly zeroing in borderline allocation/free situations.		1999-02-08 00:37:36 +00:00
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vm_machdep.c	Rip out PQ_ZERO queue. PQ_ZERO functionality is now combined in with	1999-02-08 00:37:36 +00:00