From mboxrd@z Thu Jan 1 00:00:00 1970 From: paraneetharanc@gmail.com (Paraneetharan Chandrasekaran) Date: Wed, 29 Jun 2011 13:04:34 +0530 Subject: Basic HighMeM Question In-Reply-To: References: Message-ID: To: kernelnewbies@lists.kernelnewbies.org List-Id: kernelnewbies.lists.kernelnewbies.org On 29 June 2011 12:08, Mulyadi Santosa wrote: > Hi :) > > On Wed, Jun 29, 2011 at 13:30, piyush moghe wrote: > > Thanks Mulyadi and Prabhu for your enlightening description. > > You welcome :) > > > What a plight!!! memory has become soo cheap nowadays that I don't have > less > > than 1GB system and difficult to find someone in my knowledge having less > > than 1 GB memory. > > In embedded world, it's still common scenario.... so it depends on > which side we see it :) That's the flexibility Linux kernel tries to > show...it does well on big memory machine...but it can also run in > small amount of memory... of course, with the right user space > applications :) (hint: Linux slitaz, puppy, tiny core...) > > > > Although does this means that pages in FCOM will never have page fault? > > Everything mapped in kernel space ( I stress the word "mapped") is > designed to stay all the time in RAM in Linux kernel context. So based > on that AFAIK, we won't get page fault in kernel space. This is > strictly design choice IMHO. > > >and > > if this is true is this the reason why we assign NULL to memory > descriptor ( > > mm_struct ) for kernel threads? > > because kernel threads don't need to have specific address space owned > to them. They can simply "borrow" last scheduled process' address > space. After all, they just operate in kernel space, which is the same > for all processes, be it kernel threads or normal task. > Thanks Mulyadi for your clarifications! I am not getting the idea of "borrowing" last run process's address space. A kernel thread refers only the addresses in kernel's address space (low-mem area) which is mapped already, isnt it? How does the address space of last run task comes into picture? > > -- > regards, > > Mulyadi Santosa > Freelance Linux trainer and consultant > > blog: the-hydra.blogspot.com > training: mulyaditraining.blogspot.com > > _______________________________________________ > Kernelnewbies mailing list > Kernelnewbies at kernelnewbies.org > http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies > -- Regards, Paraneetharan C -------------- next part -------------- An HTML attachment was scrubbed... URL: http://lists.kernelnewbies.org/pipermail/kernelnewbies/attachments/20110629/c7e9477e/attachment.html