[PATCH rdma-next v3 0/2] Dynamicaly allocate SG table from the pages

[Leon Romanovsky]

From: Leon Romanovsky <leonro@xxxxxxxxxx>

Changelog:
v3:
 * Squashed Christopher's suggestion to avoid introduced new API, but extend existing one.
v2: https://lore.kernel.org/linux-rdma/20200916140726.839377-1-leon@xxxxxxxxxx
 * Fixed indentations and comments
 * Deleted sg_alloc_next()
 * Squashed lib/scatterlist patches into one
v1: https://lore.kernel.org/lkml/20200910134259.1304543-1-leon@xxxxxxxxxx
 * Changed _sg_chain to be __sg_chain
 * Added dependency on ARCH_NO_SG_CHAIN
 * Removed struct sg_append
v0:
 * https://lore.kernel.org/lkml/20200903121853.1145976-1-leon@xxxxxxxxxx

--------------------------------------------------------------------------
>From Maor:

This series extends __sg_alloc_table_from_pages to allow chaining of
new pages to already initialized SG table.

This allows drivers to utilize the optimization of merging contiguous
pages without a need to pre allocate all the pages and hold them in
a very large temporary buffer prior to the call to SG table initialization.

The second patch changes the Infiniband driver to use the new API. It
removes duplicate functionality from the code and benefits the
optimization of allocating dynamic SG table from pages.

In huge pages system of 2MB page size, without this change, the SG table
would contain x512 SG entries.
E.g. for 100GB memory registration:

             Number of entries      Size
    Before        26214400          600.0MB
    After            51200            1.2MB

Thanks

Maor Gottlieb (2):
  lib/scatterlist: Add support in dynamic allocation of SG table from
    pages
  RDMA/umem: Move to allocate SG table from pages

 drivers/gpu/drm/i915/gem/i915_gem_userptr.c |  12 +-
 drivers/gpu/drm/vmwgfx/vmwgfx_ttm_buffer.c  |  15 +-
 drivers/infiniband/core/umem.c              |  92 ++----------
 include/linux/scatterlist.h                 |  43 +++---
 lib/scatterlist.c                           | 158 +++++++++++++++-----
 lib/sg_pool.c                               |   3 +-
 tools/testing/scatterlist/main.c            |   9 +-
 7 files changed, 175 insertions(+), 157 deletions(-)

--
2.26.2