On Wed, Mar 28, 2012, Orna Agmon Ben-Yehuda wrote about "More RAM than MemTotal": > So: 180Mb lost, a reward for an honest finder?
Hi Orna, I'm not sure there is just one culprit. I am guessing that MemTotal doesn't try to tell you how much memory you really have, but rather how much memory can be used. I have 3 suspects on why it's lower: 1. The "struct page" overhead. Linux hold a 56 byte (or 32 byte, on 32-bit) "struct page" for each page, and the pages holding these structures of course cannot be used for other things. This amounts to about 1.3% of your memory being "lost" for these structures. Since in your case 4.6% of the memory was "lost", it doesn't explain everything. 2. The "PCI hole". PCI devices need physical memory addresses to communicate with them (MMIO), and these addresses cannot be used as real memory. Check if your log mentions a "BIOS-provided physical RAM map" with a list of "reserved" (vs "usable") memory regions. 3. Perhaps (but I'm not sure) the MemTotal doesn't include the actual code (text and initialized data) of the Linux kernel itself. This also takes memory. Again, these are just my suspicions. Had the kernel writers wanted, they could have included all of the above in the MemTotal calculation. I don't know if they did - or what they wanted MemTotal to signify. -- Nadav Har'El | Wednesday, Mar 28 2012, [email protected] |----------------------------------------- Phone +972-523-790466, ICQ 13349191 |If at first you don't succeed, redefine http://nadav.harel.org.il |success. _______________________________________________ Linux-il mailing list [email protected] http://mailman.cs.huji.ac.il/mailman/listinfo/linux-il
