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Reload this Page why sum(bdev->bd_inode->i_mapping->nrpages) is not nr_pagecache?
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Old 06-14-2008   #1 (permalink)
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why sum(bdev->bd_inode->i_mapping->nrpages) is not nr_pagecache?
I am new to Linux Mem management, and learning...

Normally when a new page is added to radix tree, address_space nrpages is incremented by 1 as well as the global variable nr_pagecache. Same when a page is removed from the tree.

Then I do not understand why then sum(nr_pages) is much smaller (10 to 20MB) than nr_pagecache (can be x00MB)... I got those numbers from statistics reported in /proc/meminfo,

Can you hint me how to find answer?

Thanks!
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Old 06-15-2008   #2 (permalink)
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I found the answer: meminfo buffers corresponds to pages for block device file system.

On the other hand, nr_pagecache refers to all files. It includes pages for block device, swap disk and regular file file cache.
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