Thank you Michael. I am forwarding the email to another person - MinChan, not sure if he knows the answer or not?
Hello MinChan, do you know the answer to my question? Thanks. ---------- Forwarded message ---------- From: Michael Blizek <[EMAIL PROTECTED]> Date: Sat, Nov 22, 2008 at 4:53 PM Subject: Re: a question of mmap() of files into memory To: Peter Teoh <[EMAIL PROTECTED]> Cc: kernelnewbies <[email protected]> Hi! On 15:49 Sat 22 Nov , Peter Teoh wrote: > when a process mmap() a section of a file into its own process memory, > the process memory will maintain a copy of the data of that section of > the file. > > but then this is pagecache which cache the physically opened file, right? > > so...does there exists duplicated buffering? (one in kernel - > pagecache, and one in userspace - for mmap() content of the file in > process memory) > > Correct? So so...then it looks like a lot of duplicated stuff ..... When multiple programs load the same libraries into memory, they are mmap()ed and shared. I cannot tell you exactly, but I do not think that the files exist in an mmap() space and in the page cache. However, I have heared that readahead and page reclaim is differently. -Michi -- programing a layer 3+4 network protocol for mesh networks see http://michaelblizek.twilightparadox.com -- Regards, Peter Teoh -- To unsubscribe from this list: send an email with "unsubscribe kernelnewbies" to [EMAIL PROTECTED] Please read the FAQ at http://kernelnewbies.org/FAQ
