mirror of
https://github.com/raspberrypi/linux.git
synced 2025-12-27 12:32:50 +00:00
1e8e55b670
Add CQE support to the block driver, including:
- optionally using DCMD for flush requests
- "manually" issuing discard requests
- issuing read / write requests to the CQE
- supporting block-layer timeouts
- handling recovery
- supporting re-tuning
CQE offers 25% - 50% better random multi-threaded I/O. There is a slight
(e.g. 2%) drop in sequential read speed but no observable change to sequential
write.
CQE automatically sends the commands to complete requests. However it only
supports reads / writes and so-called "direct commands" (DCMD). Furthermore
DCMD is limited to one command at a time, but discards require 3 commands.
That makes issuing discards through CQE very awkward, but some CQE's don't
support DCMD anyway. So for discards, the existing non-CQE approach is
taken, where the mmc core code issues the 3 commands one at a time i.e.
mmc_erase(). Where DCMD is used, is for issuing flushes.
Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Tested-by: Linus Walleij <linus.walleij@linaro.org>
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. 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.