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From: Leon Romanovsky <>
To: Christoph Hellwig <>,
	Doug Ledford <>,
	Jason Gunthorpe <>
Cc: Leon Romanovsky <>,, Maor Gottlieb <>
Subject: [PATCH rdma-next v2 0/2] scatterlist: add sg_alloc_table_append function
Date: Wed, 16 Sep 2020 17:07:24 +0300
Message-ID: <> (raw)

From: Leon Romanovsky <>

 * Fixed indentations and comments
 * Deleted sg_alloc_next()
 * Squashed lib/scatterlist patches into one
 * Changed _sg_chain to be __sg_chain
 * Added dependency on ARCH_NO_SG_CHAIN
 * Removed struct sg_append

From Maor:

This series adds a new constructor for a scatter gather table. Like
sg_alloc_table_from_pages function, this function merges all contiguous
chunks of the pages a into single scatter gather entry.

In contrast to sg_alloc_table_from_pages, the new API allows 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 first two patches refactor the code of sg_alloc_table_from_pages
in order to have code sharing and add sg_alloc_next function to allow
dynamic allocation of more entries in the SG table.

The third patch introduces the new API.

The last 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


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

 drivers/infiniband/core/umem.c |  90 ++---------
 include/linux/scatterlist.h    |  34 ++--
 lib/scatterlist.c              | 273 ++++++++++++++++++++++++---------
 3 files changed, 234 insertions(+), 163 deletions(-)


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Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-09-16 14:07 Leon Romanovsky [this message]
2020-09-16 14:07 ` [PATCH rdma-next v2 1/2] lib/scatterlist: Add support in dynamic allocation of SG table from pages Leon Romanovsky
2020-09-21  7:57   ` Christoph Hellwig
2020-09-21  9:18     ` Leon Romanovsky
2020-09-22  6:24       ` Christoph Hellwig
2020-09-22  6:32         ` Leon Romanovsky
2020-09-25  8:19   ` [lib/scatterlist] 71606c3597: last_state.is_incomplete_run kernel test robot
2020-09-16 14:07 ` [PATCH rdma-next v2 2/2] RDMA/umem: Move to allocate SG table from pages Leon Romanovsky

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