On Tue, Oct 14, 2014 at 01:08:15PM +0100, Daniel P. Berrange wrote: > On Tue, Oct 14, 2014 at 08:02:38PM +0800, Linhaifeng wrote: > > Hi,all > > > > I was trying to use hugepage with VM and found that the hugepage not freed > > when close VM. > > > > > > 1.Before start VM the /proc/meminfo is: > > AnonHugePages: 124928 kB > > HugePages_Total: 4096 > > HugePages_Free: 3072 > > HugePages_Rsvd: 0 > > HugePages_Surp: 0 > > Hugepagesize: 2048 kB > > > > 2.Start VM the /proc/meminfo is: > > AnonHugePages: 139264 kB > > HugePages_Total: 4096 > > HugePages_Free: 2048 > > HugePages_Rsvd: 0 > > HugePages_Surp: 0 > > Hugepagesize: 2048 kB > > > > 3.Close VM the /proc/meminfo is: > > AnonHugePages: 124928 kB > > HugePages_Total: 4096 > > HugePages_Free: 2048 > > HugePages_Rsvd: 0 > > HugePages_Surp: 0 > > Hugepagesize: 2048 kB > > > > We can see there are 1024 hugepage leak! > > > > I try to found which function used to free hugepage but i'm not sure > > where the qemu_ram_free is the function to free hugepage. > > I found that the qemu_ram_free function not call unlink and we know > > unlink is used to free hugepage(see example of hugepage-mmap.c in > > kernel source). > > We can't rely on 'qemu_ram_free' ever executing because we must > ensure hugepages are freed upon QEMU crash. > > It seems we should rely on UNIX filesytstem semantics and simply > unlink the memory segment the moment we create it & open the FD. > That way the kernel will automatically free it when the FD is > closed when QEMU process exits. > > > Regards, > Daniel
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