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Filename Latest commit message Latest commit date
Chris Wilson e886196469 drm/i915: Use HW semaphores for inter-engine synchronisation on gen8+
Having introduced per-context seqno, we now have a means to identity
progress across the system without feel of rollback as befell the
global_seqno. That is we can program a MI_SEMAPHORE_WAIT operation in
advance of submission safe in the knowledge that our target seqno and
address is stable.

However, since we are telling the GPU to busy-spin on the target address
until it matches the signaling seqno, we only want to do so when we are
sure that busy-spin will be completed quickly. To achieve this we only
submit the request to HW once the signaler is itself executing (modulo
preemption causing us to wait longer), and we only do so for default and
above priority requests (so that idle priority tasks never themselves
hog the GPU waiting for others).

As might be reasonably expected, HW semaphores excel in inter-engine
synchronisation microbenchmarks (where the 3x reduced latency / increased
throughput more than offset the power cost of spinning on a second ring)
and have significant improvement (can be up to ~10%, most see no change)
for single clients that utilize multiple engines (typically media players
and transcoders), without regressing multiple clients that can saturate
the system or changing the power envelope dramatically.

v3: Drop the older NEQ branch, now we pin the signaler's HWSP anyway.
v4: Tell the world and include it as part of scheduler caps.

Testcase: igt/gem_exec_whisper
Testcase: igt/benchmarks/gem_wsim
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190301170901.8340-3-chris@chris-wilson.co.uk
2019-03-01 17:45:07 +00:00
arch Merge branch 'efi-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2019-02-17 09:22:01 -08:00
block for-linus-20190215 2019-02-15 09:12:28 -08:00
certs
crypto
Documentation Prep patches + headers for the mei-hdcp/i915 component interfaces 2019-02-20 11:53:48 +02:00
drivers drm/i915: Use HW semaphores for inter-engine synchronisation on gen8+ 2019-03-01 17:45:07 +00:00
firmware
fs Two small fixes, one for crashes using nfs/krb5 with older enctypes, one 2019-02-16 17:38:01 -08:00
include drm/i915: Use HW semaphores for inter-engine synchronisation on gen8+ 2019-03-01 17:45:07 +00:00
init Revert "mm: use early_pfn_to_nid in page_ext_init" 2019-02-12 16:33:18 -08:00
ipc
kernel Merge branch 'perf-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2019-02-17 08:38:13 -08:00
lib Compiler Attributes: Clean the new GCC 9 -Wmissing-attributes warnings 2019-02-16 10:28:05 -08:00
LICENSES
mm arm64, mm, efi: Account for GICv3 LPI tables in static memblock reserve table 2019-02-16 15:02:03 +01:00
net Two small fixes, one for crashes using nfs/krb5 with older enctypes, one 2019-02-16 17:38:01 -08:00
samples
scripts
security
sound Prep patches + headers for the mei-hdcp/i915 component interfaces 2019-02-20 11:53:48 +02:00
tools Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2019-02-15 08:00:11 -08:00
usr
virt KVM/ARM fixes for 5.0: 2019-02-13 19:39:24 +01:00
.clang-format
.cocciconfig
.get_maintainer.ignore
.gitattributes
.gitignore
.mailmap
COPYING
CREDITS
Kbuild
Kconfig
MAINTAINERS Merge https://gitlab.freedesktop.org/drm/msm into drm-next 2019-02-20 12:16:37 +10:00
Makefile Linux 5.0-rc7 2019-02-17 18:46:40 -08:00
README

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.