Silicon Investor (SI) -- The First Internet Community

STOCKTALK

We've detected that you're using an ad content blocking browser plug-in or feature. Ads provide a critical source of revenue to the continued operation of Silicon Investor. We ask that you disable ad blocking while on Silicon Investor in the best interests of our community. If you are not using an ad blocker but are still receiving this message, make sure your browser's tracking protection is set to the 'standard' level.

Technology Stocks : All About Sun Microsystems -- Ignore unavailable to you. Want to Upgrade?

To: Stormweaver who wrote (17474)	6/30/1999 12:19:00 PM
From: Jon Tara	Read Replies (1) \| Respond to of 64865

James YOU ARE WRONG! I wrote: "There is nothing to gain through physical defragmentation, because there is no additional overhead associated with the use of discontiguous pages ..." You replied: "Sure it will. If the OS has split an allocation across a page boundary then the access to that region may/will generate a PAGE FAULT; which depending on the physical memory could force the OS to load it from disk. The longer and OS is running with busy memory intensive applications (like on a server) the more memory will get fragmented." Wrong. Pages are pages are pages. And they are just as likely to be paged-out if allocated contiguously as if they are allocated discontiguously. That is, the algorithm that determines when a page is paged-out to disk is completely independant of how that page was initially allocated. A page becomes a candidate for page-out through dis-use. Period. In other words, allocation of contiguous pages does NOT exempt those pages from being paged-out! EVERY time that the OS allocates memory longer than 1 page, it IS "split across a page boundry", whether it is or is not physically contiguous. Allocate 100 discontiguous pages. Allocate 100 contiguous pages. Each page is equally likely to be paged-out (dependent solely on it's use count). Pages CAN be "locked down" and this can cause fragmentation problems. This is very rare, though, and limited primarly to device drivers needing contiguous DMA memory, and done primarly at boot time.