This Linux kernel change "[PATCH] meminfo: add Cached underflow check" is included in the Linux 2.6.12 release. This change is authored by Martin Hicks <mort [at] sgi.com> on Sat Apr 16 15:24:08 2005 -0700. The commit for this change in Linux stable tree is 4c4c402 (patch).
[PATCH] meminfo: add Cached underflow check Working on some code lately I've been getting huge values for "Cached". The cause is that get_page_cache_size() is an approximate value, and for a sufficiently small returned value of get_page_cache_size() the value underflows. Signed-off-by: Martin Hicks <firstname.lastname@example.org> Signed-off-by: Andrew Morton <email@example.com> Signed-off-by: Linus Torvalds <firstname.lastname@example.org>
There are 7 lines of Linux source code added/deleted in this change. Code changes to Linux kernel are as follows.
fs/proc/proc_misc.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/fs/proc/proc_misc.c b/fs/proc/proc_misc.c index 1d75d6a..a60a3b3 100644 --- a/fs/proc/proc_misc.c +++ b/fs/proc/proc_misc.c @@ -126,6 +126,7 @@ static int meminfo_read_proc(char *page, char **start, off_t off, unsigned long committed; unsigned long allowed; struct vmalloc_info vmi; + long cached; get_page_state(&ps); get_zone_counts(&active, &inactive, &free); @@ -140,6 +141,10 @@ static int meminfo_read_proc(char *page, char **start, off_t off, allowed = ((totalram_pages - hugetlb_total_pages()) * sysctl_overcommit_ratio / 100) + total_swap_pages; + cached = get_page_cache_size() - total_swapcache_pages - i.bufferram; + if (cached < 0) + cached = 0; + get_vmalloc_info(&vmi); /* @@ -172,7 +177,7 @@ static int meminfo_read_proc(char *page, char **start, off_t off, K(i.totalram), K(i.freeram), K(i.bufferram), - K(get_page_cache_size()-total_swapcache_pages-i.bufferram), + K(cached), K(total_swapcache_pages), K(active), K(inactive),