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[ Upstream commit1beaef29c3] For memcpy, the source pages are memset to zero only when --cycles is used. This leads to wildly different results with or without --cycles, since all sources pages are likely to be mapped to the same zero page without explicit writes. Before this fix: $ export cmd="./perf stat -e LLC-loads -- ./perf bench \ mem memcpy -s 1024MB -l 100 -f default" $ $cmd 2,935,826 LLC-loads 3.821677452 seconds time elapsed $ $cmd --cycles 217,533,436 LLC-loads 8.616725985 seconds time elapsed After this fix: $ $cmd 214,459,686 LLC-loads 8.674301124 seconds time elapsed $ $cmd --cycles 214,758,651 LLC-loads 8.644480006 seconds time elapsed Fixes:47b5757bac("perf bench mem: Move boilerplate memory allocation to the infrastructure") Signed-off-by: Vincent Whitchurch <vincent.whitchurch@axis.com> Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com> Cc: Jiri Olsa <jolsa@redhat.com> Cc: Mark Rutland <mark.rutland@arm.com> Cc: Namhyung Kim <namhyung@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: kernel@axis.com Link: http://lore.kernel.org/lkml/20200810133404.30829-1-vincent.whitchurch@axis.com Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com> Signed-off-by: Sasha Levin <sashal@kernel.org>
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.
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.