On Wed, 2016-02-10 at 11:11 -0800, Daniel Walker wrote:

On 02/10/2016 10:13 AM, Dave Hansen wrote:

quoted

On 02/10/2016 10:04 AM, Daniel Walker wrote:

quoted

quoted

[Linux_0:/]$ echo 3 > /proc/sys/vm/drop_caches
[Linux_0:/]$ cat /proc/meminfo
MemTotal:        3977836 kB
MemFree:         1095012 kB
MemAvailable:    1434148 kB

I suspect MemAvailable takes into account more than just the
droppable
caches. For instance, reclaimable slab is included, but I don't
think
drop_caches drops that part.

There's a bit for page cache and a bit for slab, see:

	https://kernel.org/doc/Documentation/sysctl/vm.txt

Ok, then this looks like a defect then. I would think MemAvailable
would 
always be smaller then MemFree (after echo 3 > 
/proc/sys/vm/drop_caches).. Unless there is something else be
accounted 
for that we aren't aware of.

echo 3 > /proc/sys/vm/drop_caches will only
drop unmapped page cache, IIRC

The system may still have a number of page
cache pages left that are mapped in processes,
but will be reclaimable if the VM needs the
memory for something else.

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