<div dir="ltr"><br><div class="gmail_extra"><br><br><div class="gmail_quote">On Mon, Mar 3, 2014 at 11:52 PM, priyaranjan <span dir="ltr"><<a href="mailto:priyaranjan45678@gmail.com" target="_blank">priyaranjan45678@gmail.com</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-color:rgb(204,204,204);border-left-style:solid;padding-left:1ex"><div dir="ltr"><div><span style="line-height:15px;font-size:12px;font-family:Arial,'Lucida Grande',sans-serif">I was going through </span><font color="#000000" face="Arial, Lucida Grande, sans-serif"><span style="font-size:12px;line-height:15px"><a href="http://linux-mm.org/HighMemory" target="_blank">http://linux-mm.org/HighMemory</a></span></font></div>
<div><font color="#000000" face="Arial, Lucida Grande, sans-serif"><span style="font-size:12px;line-height:15px"><br>"Currently the 32 bit x86 architecture is the most popular type of computer. In this architecture, traditionally the Linux kernel has split the 4GB of virtual memory address space into 3GB for user programs and 1GB for the kernel"</span></font></div>
<div><font color="#000000" face="Arial, Lucida Grande, sans-serif"><span style="font-size:12px;line-height:15px"><br></span></font></div><div><span style="line-height:15px;font-size:12px;font-family:Arial,'Lucida Grande',sans-serif">What about 64-bit system? Where does the code lie in linux kernel for the check?</span><br>
</div><div><span style="line-height:15px;font-size:12px;font-family:Arial,'Lucida Grande',sans-serif">Is there any latest and updated memory management documentation for Linux kernel?</span><br></div>
<div><br></div><div>Regards,</div><div>Priyaranjan</div><div><font color="#000000" face="Arial, Lucida Grande, sans-serif"><span style="font-size:12px;line-height:15px"><br></span></font></div></div></blockquote><div><br>
</div><div>Priyaranjan,</div><div><br></div><div>As below link suggests:</div><a href="http://users.nccs.gov/~fwang2/linux/lk_addressing.txt" target="_blank" style="font-size:13px;font-family:arial,sans-serif">http://users.nccs.gov/~fwang2/linux/lk_addressing.txt</a><br>
<div><br></div><div>Also read this blog written in chinese: </div><div><br></div><div><a href="http://adam8157.info/blog/2012/07/linux-x86-64-vm/">http://adam8157.info/blog/2012/07/linux-x86-64-vm/</a></div><div><br></div>
<div>on 64 bit arch the virtual address space is huge (2 to thr power of 64). So the overhead of translating the virtual addresses will be high. TO avoid this only lower 48 bits are used to form virtual addresses. This virtual space will still be very large (256 TB) and hence the user/kernel split is 1:1 (128TB:128TB). And as suggested in link it is very unlikely that you will have such a huge RAM(more than 128TB) installed on any machine there is no concept of HIGHMEM.</div>
<div><br></div><div>Hope this clears the air a bit. </div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-color:rgb(204,204,204);border-left-style:solid;padding-left:1ex">
<div dir="ltr"><div><font color="#000000" face="Arial, Lucida Grande, sans-serif"><span style="font-size:12px;line-height:15px"></span></font></div></div>
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<br></blockquote></div><br><br clear="all"><div><br></div>-- <br>Thanks and Regards<br>Pramod<br>
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