<div dir="ltr"><div><div>Is this is a question that popped up to your mind arbitrarily or do you have a specific system at hand which triggered you to ponder over the design of the kernel ? I felt the answer to this question is not straight forward but is multi faceted and to be discussed in a specific context. <br>
</div></div><br><div><div><div><div class="gmail_extra"><br><div class="gmail_quote">On Sat, May 11, 2013 at 9:02 AM, Paul Davies C <span dir="ltr"><<a href="mailto:pauldaviesc@gmail.com" target="_blank">pauldaviesc@gmail.com</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div dir="ltr"><br clear="all"><div>In a system with 3:1 split, the ZONE_NORMAL with a size of 896MB is permanently mapped to the kernel address space.This leaves a 128MB free space in the Kernel address space and according to my understanding, the ZONE_HIGHMEM pages are mapped temporarily to this 128MB part. If the system actually had a 4GB physical memory you will be mapping(not smultaneously) the HIHGMEM part- which is roughly 3.2GB - to this 128MB part. If that was the case Kernel would have to frequently access HIHGMEM which implicates a frequent change in temporaty mapping and that in my view is a penalty. So what was the reason why ZONE_NORMAL fixed at 896MB and not something really lower?<span class=""><font color="#888888"><br>
</font></span></div><span class=""><font color="#888888"><div><br></div>-- <br><div><font color="#C0C0C0" face="'arial narrow', sans-serif"><b>Regards,</b></font></div><div><font color="#C0C0C0" face="'arial narrow', sans-serif"><b>Paul Davies C</b></font></div>
<a href="http://vivafoss.blogspot.com" target="_blank">vivafoss.blogspot.com</a>
</font></span></div><br></blockquote></div><br>-- <br>Regards,<br>Prabhunath G<br>Linux Trainer<br>Bangalore<br>
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