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powerpc: Implement tick broadcast IPI as a fixed IPI message

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For scalability and performance reasons, we want the tick broadcast IPIs
to be handled as efficiently as possible. Fixed IPI messages
are one of the most efficient mechanisms available - they are faster than
the smp_call_function mechanism because the IPI handlers are fixed and hence
they don't involve costly operations such as adding IPI handlers to the target
CPU's function queue, acquiring locks for synchronization etc.

Luckily we have an unused IPI message slot, so use that to implement
tick broadcast IPIs efficiently.

Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
[Functions renamed to tick_broadcast* and Changelog modified by
 Preeti U. Murthy<preeti@linux.vnet.ibm.com>]
Signed-off-by: Preeti U. Murthy <preeti@linux.vnet.ibm.com>
Acked-by: Geoff Levand <geoff@infradead.org> [For the PS3 part]
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
This commit is contained in:
Srivatsa S. Bhat
2014-02-26 05:37:43 +05:30
committed by Benjamin Herrenschmidt
parent 402d9a1e02
commit 1b67bee129
6 changed files with 26 additions and 7 deletions
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2
arch/powerpc/platforms/ps3/smp.c
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@@ -76,7 +76,7 @@ static int __init ps3_smp_probe(void)
BUILD_BUG_ON(PPC_MSG_CALL_FUNCTION != 0);
BUILD_BUG_ON(PPC_MSG_RESCHEDULE != 1);
BUILD_BUG_ON(PPC_MSG_UNUSED != 2);
BUILD_BUG_ON(PPC_MSG_TICK_BROADCAST != 2);
BUILD_BUG_ON(PPC_MSG_DEBUGGER_BREAK != 3);
for (i = 0; i < MSG_COUNT; i++) {