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fd1d882c4c
There can be a significant gap in memset/memcpy performance depending
on the size of the region being operated on.
With chunk-size=4kb:
$ echo madvise > /sys/kernel/mm/transparent_hugepage/enabled
$ perf bench mem memset -p 4kb -k 4kb -s 4gb -l 10 -f x86-64-stosq
# Running 'mem/memset' benchmark:
# function 'x86-64-stosq' (movsq-based memset() in arch/x86/lib/memset_64.S)
# Copying 4gb bytes ...
13.011655 GB/sec
With chunk-size=1gb:
$ echo madvise > /sys/kernel/mm/transparent_hugepage/enabled
$ perf bench mem memset -p 4kb -k 1gb -s 4gb -l 10 -f x86-64-stosq
# Running 'mem/memset' benchmark:
# function 'x86-64-stosq' (movsq-based memset() in arch/x86/lib/memset_64.S)
# Copying 4gb bytes ...
21.936355 GB/sec
So, allow the user to specify the chunk-size.
The default value is identical to the total size of the region, which
preserves current behaviour.
Reviewed-by: Namhyung Kim <namhyung@kernel.org>
Signed-off-by: Ankur Arora <ankur.a.arora@oracle.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: Mateusz Guzik <mjguzik@gmail.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Raghavendra K T <raghavendra.kt@amd.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
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 reStructuredText 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.