LKML Archive on lore.kernel.org
 help / color / Atom feed
* [RFC] avoid indirect calls for DMA direct mappings v2
@ 2018-12-07 19:07 Christoph Hellwig
  2018-12-07 19:07 ` [PATCH 01/15] swiotlb: remove SWIOTLB_MAP_ERROR Christoph Hellwig
                   ` (17 more replies)
  0 siblings, 18 replies; 41+ messages in thread
From: Christoph Hellwig @ 2018-12-07 19:07 UTC (permalink / raw)
  To: iommu, Linus Torvalds, Jesper Dangaard Brouer
  Cc: Tariq Toukan, Ilias Apalodimas, Toke Høiland-Jørgensen,
	Robin Murphy, Konrad Rzeszutek Wilk, Tony Luck, Fenghua Yu,
	Marek Szyprowski, Keith Busch, Jonathan Derrick, linux-pci,
	linux-ia64, x86, linux-kernel

Hi all,

a while ago Jesper reported major performance regressions due to the
spectre v2 mitigations in his XDP forwarding workloads.  A large part
of that is due to the DMA mapping API indirect calls.

It turns out that the most common implementation of the DMA API is the
direct mapping case, and now that we have merged almost all duplicate
implementations of that into a single generic one is easily feasily to
direct calls for this fast path.

This series adds consolidate the DMA mapping code by merging the
swiotlb case into the dma direct case, and then treats NULL dma_ops
as an indicator that that we should directly call the direct mapping
case.  This recovers a large part of the retpoline induces XDP slowdown.

This works is based on the dma-mapping tree, so you probably want to
want this git tree for testing:

    git://git.infradead.org/users/hch/misc.git dma-direct-calls.2

Gitweb:

    http://git.infradead.org/users/hch/misc.git/shortlog/refs/heads/dma-direct-calls.2

Changes since v1:
 - now also includes all the prep patches relative to the dma-mapping
   for-next tree
 - move various slow path functions out of line
 - use a NULL dma ops as the indicate to use the direct mapping path
 - remove dma_direct_ops now that we always call it without the indirection
 - move the dummy dma ops to common code
 - explicitly st the dummy dma ops for devices that are indicates as not
   DMA capable by firmware

^ permalink raw reply	[flat|nested] 41+ messages in thread

end of thread, back to index

Thread overview: 41+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2018-12-07 19:07 [RFC] avoid indirect calls for DMA direct mappings v2 Christoph Hellwig
2018-12-07 19:07 ` [PATCH 01/15] swiotlb: remove SWIOTLB_MAP_ERROR Christoph Hellwig
2018-12-07 19:07 ` [PATCH 02/15] swiotlb: remove dma_mark_clean Christoph Hellwig
2019-01-02 21:53   ` Tony Luck
2019-01-03  7:23     ` Christoph Hellwig
2019-01-03 17:35       ` Tony Luck
2019-01-04  8:09         ` Christoph Hellwig
2018-12-07 19:07 ` [PATCH 03/15] dma-direct: improve addressability error reporting Christoph Hellwig
2018-12-07 19:07 ` [PATCH 04/15] dma-direct: use dma_direct_map_page to implement dma_direct_map_sg Christoph Hellwig
2018-12-07 19:07 ` [PATCH 05/15] dma-direct: merge swiotlb_dma_ops into the dma_direct code Christoph Hellwig
2018-12-07 19:07 ` [PATCH 06/15] dma-mapping: simplify the dma_sync_single_range_for_{cpu,device} implementation Christoph Hellwig
2018-12-07 19:07 ` [PATCH 07/15] dma-mapping: merge dma_unmap_page_attrs and dma_unmap_single_attrs Christoph Hellwig
2018-12-07 19:07 ` [PATCH 08/15] dma-mapping: move dma_get_required_mask to kernel/dma Christoph Hellwig
2018-12-07 19:07 ` [PATCH 09/15] dma-mapping: move various slow path functions out of line Christoph Hellwig
2018-12-07 19:07 ` [PATCH 10/15] dma-mapping: move dma_cache_sync " Christoph Hellwig
2018-12-07 19:07 ` [PATCH 11/15] dma-mapping: always build the direct mapping code Christoph Hellwig
2018-12-07 19:07 ` [PATCH 12/15] dma-mapping: factor out dummy DMA ops Christoph Hellwig
2018-12-07 19:07 ` [PATCH 13/15] ACPI / scan: Refactor _CCA enforcement Christoph Hellwig
2018-12-14 21:15   ` Bjorn Helgaas
2018-12-07 19:07 ` [PATCH 14/15] vmd: use the proper dma_* APIs instead of direct methods calls Christoph Hellwig
2018-12-14 21:17   ` Bjorn Helgaas
2018-12-14 21:34     ` Derrick, Jonathan
2018-12-07 19:07 ` [PATCH 15/15] dma-mapping: bypass indirect calls for dma-direct Christoph Hellwig
2018-12-14 14:11   ` Marek Szyprowski
2018-12-14 14:24     ` Christoph Hellwig
2018-12-14 14:32       ` Marek Szyprowski
2018-12-15 17:46   ` [15/15] " Guenter Roeck
2018-12-16  9:02     ` Christoph Hellwig
2018-12-18 20:34   ` Guillaume Tucker
2018-12-18 20:42     ` Robin Murphy
2018-12-19  6:42       ` Christoph Hellwig
2018-12-20 16:44   ` [PATCH 15/15] " Thierry Reding
2018-12-20 16:46     ` Christoph Hellwig
2018-12-08 16:06 ` [RFC] avoid indirect calls for DMA direct mappings v2 Jesper Dangaard Brouer
2018-12-08 16:50   ` Christoph Hellwig
2018-12-10 21:51 ` Luck, Tony
2018-12-11  6:51   ` Christoph Hellwig
2018-12-11 16:42     ` Luck, Tony
2018-12-11 17:13     ` Luck, Tony
2018-12-11 17:15       ` Christoph Hellwig
2018-12-13 20:08 ` Christoph Hellwig

LKML Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/lkml/0 lkml/git/0.git
	git clone --mirror https://lore.kernel.org/lkml/1 lkml/git/1.git
	git clone --mirror https://lore.kernel.org/lkml/2 lkml/git/2.git
	git clone --mirror https://lore.kernel.org/lkml/3 lkml/git/3.git
	git clone --mirror https://lore.kernel.org/lkml/4 lkml/git/4.git
	git clone --mirror https://lore.kernel.org/lkml/5 lkml/git/5.git
	git clone --mirror https://lore.kernel.org/lkml/6 lkml/git/6.git
	git clone --mirror https://lore.kernel.org/lkml/7 lkml/git/7.git
	git clone --mirror https://lore.kernel.org/lkml/8 lkml/git/8.git
	git clone --mirror https://lore.kernel.org/lkml/9 lkml/git/9.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 lkml lkml/ https://lore.kernel.org/lkml \
		linux-kernel@vger.kernel.org
	public-inbox-index lkml

Example config snippet for mirrors

Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.kernel.vger.linux-kernel


AGPL code for this site: git clone https://public-inbox.org/public-inbox.git