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Subject: Qestion about page->_count and page reclaim
From: Li Haifeng <omycle@gmail.com>
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Hi, all in kernel.

The page->_count is the page frame's usage count.
When page is allocated, the page will be refcounted, and page->_cout will
be set 1.

After be allocated from buddy system, the page will be used by process.
 get_page and put_page/put_page_testzero will used in pairs. is it right?

When the page is reclaimed to buddy system, the page->_count should be 0.
However, Because the initialization of page->_count is 1, get_page() and
put_page() is called in pairs, I coufused how page->_count will be 0?

Thanks.

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Content-Type: text/html; charset=ISO-8859-1
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<div dir=3D"ltr"><span style=3D"color:rgb(0,0,0);font-family:arial,sans-ser=
if;font-size:14px">Hi, all in kernel.</span><div style=3D"color:rgb(0,0,0);=
font-family:arial,sans-serif;font-size:14px"><br></div><div style=3D"color:=
rgb(0,0,0);font-family:arial,sans-serif;font-size:14px">
The page-&gt;_count is the page frame&#39;s usage count.</div><div style=3D=
"color:rgb(0,0,0);font-family:arial,sans-serif;font-size:14px">When page is=
 allocated, the page will be refcounted, and page-&gt;_cout will be set 1.<=
/div>
<div style=3D"color:rgb(0,0,0);font-family:arial,sans-serif;font-size:14px"=
><br></div><div style=3D"color:rgb(0,0,0);font-family:arial,sans-serif;font=
-size:14px">After be allocated from buddy system, the page will be used by =
process. =A0get_page and put_page/put_page_testzero will used in pairs. is =
it right?</div>
<div style=3D"color:rgb(0,0,0);font-family:arial,sans-serif;font-size:14px"=
><br></div><div style=3D"color:rgb(0,0,0);font-family:arial,sans-serif;font=
-size:14px">When the page is reclaimed to buddy system, the page-&gt;_count=
 should be 0. However, Because the initialization of page-&gt;_count is 1, =
get_page() and put_page() is called in pairs, I coufused how page-&gt;_coun=
t will be 0? =A0=A0</div>
<div style=3D"color:rgb(0,0,0);font-family:arial,sans-serif;font-size:14px"=
><br></div><div style=3D"color:rgb(0,0,0);font-family:arial,sans-serif;font=
-size:14px">Thanks.</div></div>

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