Re: [PATCH rdma-next 1/4] lib/scatterlist: Refactor sg_alloc_table_from_pages

[Maor Gottlieb]

On 9/7/2020 10:29 AM, Christoph Hellwig wrote:
> On Thu, Sep 03, 2020 at 06:54:34PM +0300, Leon Romanovsky wrote:
> > From: Maor Gottlieb <maorg@xxxxxxxxxx>
> >
> > Currently, sg_alloc_table_from_pages doesn't support dynamic chaining of
> > SG entries. Therefore it requires from user to allocate all the pages in
> > advance and hold them in a large buffer. Such a buffer consumes a lot of
> > temporary memory in HPC systems which do a very large memory registration.
> >
> > The next patches introduce API for dynamically allocation from pages and
> > it requires us to do the following:
> >   * Extract the code to alloc_from_pages_common.
> >   * Change the build of the table to iterate on the chunks and not on the
> >     SGEs. It will allow dynamic allocation of more SGEs.
> >
> > Since sg_alloc_table_from_pages allocate exactly the number of chunks,
> > therefore chunks are equal to the number of SG entries.
> Given how few users __sg_alloc_table_from_pages has, what about just
> switching it to your desired calling conventions without another helper?

I tried it now. It didn't save a lot.  Please give me your decision and 
if needed I will update accordingly.