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tmpfs has become much more widely used since distributions use it for /tmp (Fedora 18+). In /proc/meminfo, memory used by tmpfs is accounted into "Cached" (aka "NR_FILE_PAGES", http://lxr.free-electrons.com/source/mm/shmem.c#L301 ). The tools just pass it on, so what top, free and vmstat report as "cached" is the sum of page cache and tmpfs. free has the extremely useful "-/+ buffers/cache" output. However, now that tmpfs is accounted into "cached", those numbers are way off once you have big files in /tmp. Fortunately, kernel 2.6.32 introduces "Shmem", which makes tmpfs memory usage accessible from userspace ( https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=4b02108ac1b3354a22b0d83c684797692efdc395 ). This patch substracts Shmem from Cached to get the actual page cache memory. This makes both issues mentioned above disappear. For older kernels, Shmem is not available (hence zero) and this patch is no-op. Additionally: * Update the man pages of free and vmstat to explain what is happening * Finally drop "MemShared" from the /proc/meminfo parser, it has been dead for 10+ years and is only causing confusion ( removed in kernel 2.5.54, see https://git.kernel.org/cgit/linux/kernel/git/tglx/history.git/commit/?id=fe04e9451e5a159247cf9f03c615a4273ac0c571 )
COMPATIBILITY
This code is intended for use with Linux 2.6.xx, 3.x and
hopefully all future kernels.
INSTALLATION
If you are using git version of the project you need extra step.
./autogen.sh
After that, and everyone using .tar.xz version of procps-ng, can
do normal build. Read './configure --help' to select options for
your needs.
./configure
make
make install
If you have DejaGNU installed you can run optional test suite.
make check
HOW TO CONTRIBUTE
See Documentation/BUGS file.
PACKAGING
If you are a downstream maintainer (packager) for a Linux
distribution, please avoid causing troubles. This section
applies to you.
Avoid maintaining distribution specific patches. Send your
patches to upstream, where they are at least reviewed, if not
included.
Please forward bug reports. If your bug database is public and
busy enough to bother with, please make this known. Follow
Debian's lead in making the bug database easy to comment on via
email without need for an account.
For normal packages, ensure that you do not add debugging flags
to the CFLAGS variable.
UPSTREAM & BUG REPORTS
procps-ng <procps@freelists.org>