lkml.org 
[lkml]   [2017]   [May]   [7]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
SubjectRE: [virtio-dev] Re: [PATCH v9 2/5] virtio-balloon: VIRTIO_BALLOON_F_BALLOON_CHUNKS
Date
On 05/06/2017 06:26 AM, Michael S. Tsirkin wrote:
> On Thu, Apr 27, 2017 at 02:31:49PM +0800, Wei Wang wrote:
> > On 04/27/2017 07:20 AM, Michael S. Tsirkin wrote:
> > > On Wed, Apr 26, 2017 at 11:03:34AM +0000, Wang, Wei W wrote:
> > > > Hi Michael, could you please give some feedback?
> > > I'm sorry, I'm not sure feedback on what you are requesting.
> > Oh, just some trivial things (e.g. use a field in the header,
> > hdr->chunks to indicate the number of chunks in the payload) that
> > wasn't confirmed.
> >
> > I will prepare the new version with fixing the agreed issues, and we
> > can continue to discuss those parts if you still find them improper.
> >
> >
> > >
> > > The interface looks reasonable now, even though there's a way to
> > > make it even simpler if we can limit chunk size to 2G (in fact 4G -
> > > 1). Do you think we can live with this limitation?
> > Yes, I think we can. So, is it good to change to use the previous
> > 64-bit chunk format (52-bit base + 12-bit size)?
>
> This isn't what I meant. virtio ring has descriptors with a 64 bit address and 32 bit
> size.
>
> If size < 4g is not a significant limitation, why not just use that to pass
> address/size in a standard s/g list, possibly using INDIRECT?

OK, I see your point, thanks. Post the two options here for an analysis:
Option1 (what we have now):
struct virtio_balloon_page_chunk {
__le64 chunk_num;
struct virtio_balloon_page_chunk_entry entry[];
};
Option2:
struct virtio_balloon_page_chunk {
__le64 chunk_num;
struct scatterlist entry[];
};

I don't have an issue to change it to Option2, but I would prefer Option1,
because I think there is no be obvious difference between the two options,
while Option1 appears to have little advantages here:
1) "struct virtio_balloon_page_chunk_entry" has smaller size than
"struct scatterlist", so the same size of allocated page chunk buffer
can hold more entry[] using Option1;
2) INDIRECT needs on demand kmalloc();
3) no 4G size limit;

What do you think?

Best,
Wei



\
 
 \ /
  Last update: 2017-05-07 23:42    [W:0.452 / U:0.136 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site