Hello,
Thank you very much for helping me. Before I see your reply, I enlarged my program and I saw more page faults in code segment. Now I know there is something called fault-around.
I read the Chapter 16 of the ULK which introduces file access. I started to know a technique called read-ahead from this chapter. So what's the difference or relationship between fault-around and read-ahead? I think they are used in different areas (layers) but have the same idea. Am I right?
Best regards
At 2014-11-04 21:13:56, "Kirill A. Shutemov" <kirill@xxxxxxxxxxxxx> wrote: >On Tue, Nov 04, 2014 at 07:41:08PM +0700, Mulyadi Santosa wrote: >> Hello... >> >> how big is your binary anyway? >> >> from your log, if my calculation is right, your code segment is around 330 >> KiB. But bear in mind, that not all of them are your code. There are other >> code like PLT, function prefix and so on. >> >> Also, even if your code is big, are you sure all of them are executed? >> Following 20/80 principle, most of the time, when running an application, >> only 20% portion of the application are really used/executed during 80% of >> application lifetime. The rest, it might untouched at all. >> >> >> On Thu, Oct 30, 2014 at 2:10 PM, 秦弋戈 <michaelbest002@xxxxxxx> wrote: >> >> > >> > >> > >> > Dear all, >> > >> > >> > I am a kernel newbie who want's to learn more about memory management. >> > Recently I'm doing some experiment on page fault handler. There happened >> > something that I couldn't understand. >> > >> > >> > From reading the book Understanding the Linux Kernel, I know that the >> > kernel loads a page as late as possible. It's only happened when the >> > program has to reference (read, write, or execute) a page yet the page is >> > not in memory. >> > >> > >> > However, when I traced all page faults in my test program, I found >> > something strange. My test program is large enough, but there are only two >> > page faults triggered in the code segment of the program, while most of the >> > faults are not in code segment. >> > >> > >> > At first I thought that perhaps the page is not the normal 4K page. Thus I >> > turned off the PAE support in the config file. But the log remains >> > unchanged. >> > >> > >> > So why are there only 2 page faults in code segment? It shouldn't be like >> > this in my opinion. Please help me. > >We have "faultaround" feature in recent kernel which tries to map 64k with >one page fault if the pages are already in page cache. There's handle in >debugfs to disable the feature, if you want to play with this. > >> > The attachment is my kernel log. Limited by the mail size, I couldn't >> > upload my program, but I believe that the log is clear enough. >> > >> > >> > Thank you very much. >> > Best regards >> > >> > >> > _______________________________________________ >> > Kernelnewbies mailing list >> > Kernelnewbies@xxxxxxxxxxxxxxxxx >> > http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies >> > >> > >> >> >> -- >> regards, >> >> Mulyadi Santosa >> Freelance Linux trainer and consultant >> >> blog: the-hydra.blogspot.com >> training: mulyaditraining.blogspot.com > >-- > Kirill A. Shutemov
_______________________________________________ Kernelnewbies mailing list Kernelnewbies@xxxxxxxxxxxxxxxxx http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
