Re: [dpdk-dev] vhost-user technical isssues

["Xie, Huawei" <huawei.xie@intel.com>]

I tested with latest qemu(with offset fix) in vhost app(not with test case), unmap succeeds only when the size is aligned to 1GB(hugepage size).

Another important thing is  could we do mmap(0, region[i].memory_size, PROT_XX, mmap_offset) rather than with offset 0? With the region above 4GB, we will waste 4GB address space. Or we at least need to round down offset to nearest 1GB, and round up memory size to upper 1GB, to save some address space waste.

Anyway, this is ugly. Kernel doesn't take care of us, do those alignment for us automatically.

> -----Original Message-----
> From: Tetsuya Mukawa [mailto:mukawa@igel.co.jp]
> Sent: Thursday, November 13, 2014 11:57 PM
> To: Linhaifeng; Xie, Huawei
> Cc: dev@dpdk.org
> Subject: Re: [dpdk-dev] vhost-user technical isssues
> 
> Hi Lin,
> (2014/11/14 14:30), Linhaifeng wrote:
> >
> > On 2014/11/14 13:12, Tetsuya Mukawa wrote:
> >> ease try another value like 6000MB
> > i have try this value 6000MB.I can munmap success.
> >
> > you mmap with size "memory_size + memory_offset" should also munmap
> with this size.
> >
> I appreciate for your testing and sugesstions. :)
> I am not sure what is difference between your environment and my
> environment.
> 
> Here is my code and message from the code.
> ---------------------------------------------
> [code]
> ---------------------------------------------
> size = memory.regions[i].memory_size + memory.regions[i].mmap_offset;
> 
> guest_mem = mmap(0, size, PROT_READ | PROT_WRITE,
> MAP_SHARED, fds[i], 0);
> 
> fprintf(stderr, "region=%d, mmap=%p, size=%lu\n", i, guest_mem, size);
> 
> g_assert(guest_mem != MAP_FAILED);
> 
> ret = munmap(guest_mem, size);
> 
> fprintf(stderr, "region=%d, munmap=%p, size=%lu, ret=%d\n",
> i, guest_mem, size, ret);
> 
> ---------------------------------------------
> [messages]
> ---------------------------------------------
> region=0, mmap=0x2aaac0000000, size=6291456000
> region=0, munmap=0x2aaac0000000, size=6291456000, ret=-1
> 
> With your environment, 'ret' will be 0.
> In my environment, 'size' should be aligned not to get error.
> Anyway, it's nice to implement more simple.
> When munmap failure occurs, let's think it again.
> 
> Thanks,
> Tetsuya