The hash_64() function historically does the multiply by the
GOLDEN_RATIO_PRIME_64 number with explicit shifts and adds, because
unlike the 32-bit case, gcc seems unable to turn the constant multiply
into the more appropriate shift and adds when required.
However, that means that we generate those shifts and adds even when the
architecture has a fast multiplier, and could just do it better in
hardware.
Use the now-cleaned-up CONFIG_ARCH_HAS_FAST_MULTIPLIER (together with
"is it a 64-bit architecture") to decide whether to use an integer
multiply or the explicit sequence of shift/add instructions.
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
We introduce a new hashing library that is meant to be used in
the contexts where speed is more important than uniformity of the
hashed values. The hash library leverages architecture specific
implementation to achieve high performance and fall backs to
jhash() for the generic case.
On Intel-based x86 architectures, the library can exploit the crc32l
instruction, part of the Intel SSE4.2 instruction set, if the
instruction is supported by the processor. This implementation
is twice as fast as the jhash() implementation on an i7 processor.
Additional architectures, such as Arm64 provide instructions for
accelerating the computation of CRC, so they could be added as well
in follow-up work.
Signed-off-by: Francesco Fusco <ffusco@redhat.com>
Signed-off-by: Daniel Borkmann <dborkman@redhat.com>
Signed-off-by: Thomas Graf <tgraf@redhat.com>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: David S. Miller <davem@davemloft.net>
Because hash_64() is called from the get_kprobe() inside
int3 handler, kernel causes int3 recursion and crashes if
kprobes user puts a probe on it.
Usually hash_64() is inlined into caller function, but in
some cases, it has instances by gcc's interprocedural
constant propagation.
This patch uses __always_inline instead of inline to
prevent gcc from doing such things.
Reported-by: Timo Juhani Lindfors <timo.lindfors@iki.fi>
Signed-off-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Acked-by: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Cc: Pavel Emelyanov <xemul@parallels.com>
Cc: Jiri Kosina <jkosina@suse.cz>
Cc: Nadia Yvette Chambers <nyc@holomorphy.com>
Cc: yrl.pp-manager.tt@hitachi.com
Cc: David S. Miller <davem@davemloft.net>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: http://lkml.kernel.org/r/20130314115230.19690.39387.stgit@mhiramat-M0-7522
Signed-off-by: Ingo Molnar <mingo@kernel.org>
I've legally changed my name with New York State, the US Social Security
Administration, et al. This patch propagates the name change and change
in initials and login to comments in the kernel source as well.
Signed-off-by: Nadia Yvette Chambers <nyc@holomorphy.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
Eric noticed, that when there will be devices with equal indices, some
hash functions that use them will become less effective as they could.
Fix this in advance by mixing the net_device address into the hash value
instead of the device index.
This is true for arp and ndisc hash fns. The netlabel, can and llc ones
are also ifindex-based, but that three are init_net-only, thus will not
be affected.
Many thanks to David and Eric for the hash32_ptr implementation!
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Followup to 33dd4e0ec9 "mm: make some struct page's const" which missed the
HASHED_PAGE_VIRTUAL case.
Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Michel Lespinasse <walken@google.com>
Cc: Mel Gorman <mel@csn.ul.ie>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
The 32-bit version is more efficient (and apparently gives better hash
results than the 64-bit version), so users who are only hashing a 32-bit
quantity can now opt to use the 32-bit version explicitly, rather than
promoting to a long.
Signed-off-by: Matthew Wilcox <willy@linux.intel.com>
Cc: William Lee Irwin III <wli@holomorphy.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Initial git repository build. I'm not bothering with the full history,
even though we have it. We can create a separate "historical" git
archive of that later if we want to, and in the meantime it's about
3.2GB when imported into git - space that would just make the early
git days unnecessarily complicated, when we don't have a lot of good
infrastructure for it.
Let it rip!
Linus Torvalds