hi.. On Mon, Sep 20, 2010 at 19:30, mohit verma <mohit89mlnc@xxxxxxxxx> wrote: > thanks guys, > but the problem is : > what is the need of page aligned address? as we have given starting > address 5000 and the length 1000 ( in the example by prabhu) so it should > start from that location. I think it is due to two reasons: 1. on some architecture, non page aligned access could mean trap/exception. Well, x86 is immune in this case...but if you wanna make your code safely portable, I think it's a must. 2. By making it page aligned, at least you reduce fragmentation. How come? Let's assume you just have 8K address space. You allocate a memory starting at 3K as large as 4K. That means you occupy 3K up to 7K address. What's left? 0-1 K and 7-8 K, right? And what if you wanna allocate another 4K? Yes, a page can fit that...but not mapping. We can't split below page granularity, so at least we need two page. one is mapped to 0-1 K, the other is for 7-8K. It's 2 page vs 3 page case. Yes, there's slab...but if we can allocate straight in page size granularity, things would be simpler, right? -- regards, Mulyadi Santosa Freelance Linux trainer and consultant blog: the-hydra.blogspot.com training: mulyaditraining.blogspot.com -- To unsubscribe from this list: send an email with "unsubscribe kernelnewbies" to ecartis@xxxxxxxxxxxx Please read the FAQ at http://kernelnewbies.org/FAQ
