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Re: [Qemu-devel] [PATCH v6 08/33] exec: allow memory to be allocated fro


From: Xiao Guangrong
Subject: Re: [Qemu-devel] [PATCH v6 08/33] exec: allow memory to be allocated from any kind of path
Date: Sat, 31 Oct 2015 23:56:35 +0800
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.3.0



On 10/31/2015 09:55 PM, Eduardo Habkost wrote:
On Sat, Oct 31, 2015 at 03:44:39PM +0800, Xiao Guangrong wrote:
On 10/30/2015 10:04 PM, Vladimir Sementsov-Ogievskiy wrote:
On 30.10.2015 08:56, Xiao Guangrong wrote:
Currently file_ram_alloc() is designed for hugetlbfs, however, the memory
of nvdimm can come from either raw pmem device eg, /dev/pmem, or the file
locates at DAX enabled filesystem

So this patch let it work on any kind of path

Signed-off-by: Xiao Guangrong <address@hidden>
[...]
-    block->mr->align = hpagesize;
-    if (memory < hpagesize) {
+    if (pagesize == getpagesize()) {
+        fprintf(stderr, "Memory is not allocated from HugeTlbfs.\n");
+    }

It is strange to see this warning every time.

Shouldn't the differentiation be done explicitly in command line? May be 
separate option mem-tlb, or
separate flag tlbfs=on, or for new feature - new option mem-file, or prefixes 
for paths (tlbfs://,
file://).. Or the other way to not mix things but split them.

This is just a reminder to users. Currently Qemu do not stop user to append a 
regular file
for its backend memory, particularly, hugetlbfs is not the only way to use 
HugePage for
the THP-enabled system.

We can implement your idea as a independent patchset in the future.

Isn't the whole point of this patch to make the code not specific to
hugetlbfs anymore? It makes the warning obsolete.


Before this patchset, this warning still can be triggered, for example, we
can specify the @path to /tmp/

I agree this warning could be improved, but let us do it independently.



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