[Qemu-devel] [Question] Qemu's Heap Becomes Very Large and Never Reduce Down

[Xulei (Stone)]

Hi, guys

I met a strange problem, with qemu 2.8.1:
qemu consumes too many heap memory after several operations and can not release 
them anymore:
hot pulg/unplug disk & net, vnc connect/disconnect, guestOS reboot, etc.


01a7a000-3b4efe000 rw-p 00000000 00:00 0                                 [heap]

Size:           15520272 kB

Rss:            14421836 kB

Pss:            14421836 kB

Shared_Clean:          0 kB

Shared_Dirty:          0 kB

Private_Clean:      1164 kB

Private_Dirty:  14420672 kB

Referenced:      7485624 kB

Anonymous:      14421836 kB

AnonHugePages:     34816 kB

Swap:            1098140 kB

KernelPageSize:        4 kB

MMUPageSize:           4 kB

Locked:                0 kB

VmFlags: rd wr mr mw me ac sd

My steps are:
1) start several VMs all equipped only 8G memory;
2) random combining those operations mentioned above;
3) after few hours, qemu's Virt memory and RSS both grow too large and never 
fall down;

After analysis via /proc/$pid/smaps, I found the VMA of pc.ram does not occupy 
much
memory but only becauses of heap section.

I guess that has some relations of glibc or qemu rcu_thread, but i can not 
figure it out.
Is there some patches can fix this problem or does somebody have any idea?
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