How to controll Buffers to be dilligently reclaimed?

[Cheng Rk <crquan@ymail.com>]

Hi,

I have a system that application is doing a loop on top of block device,
(which I think is stupid,)
as more and more memory goes into Buffers, then applications started
to get -ENOMEM or be oom-killed later (depends on vm.overcommit_memory setting)


In this case, if I do a manual reclaim (echo 3 > /proc/sys/vm/drop_caches)
I see 90+% of the Buffers is reclaimable, but why it's not reclaimed
to fullfill applications' memory allocation request?



-bash-4.2$ sudo losetup -a
/dev/loop0: [0005]:16512 (/dev/dm-2)
-bash-4.2$ free -m
                     total          used         free      shared       buffers     cached
Mem:             48094        46081         2012              40           40324   2085
-/+ buffers/cache:             3671        44422
Swap:             8191                5         8186


I've tried sysctl mm.vfs_cache_pressure=10000 but that seems working to Cached
memory, I wonder is there another sysctl for reclaming Buffers?


Thanks,

- Derek

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