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padata: make the sequence counter an atomic_t

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Using a spinlock to atomically increase a counter sounds wrong -- we've
atomic_t for this!

Also move 'seq_nr' to a different cache line than 'lock' to reduce cache
line trashing. This has the nice side effect of decreasing the size of
struct parallel_data from 192 to 128 bytes for a x86-64 build, e.g.
occupying only two instead of three cache lines.

Those changes results in a 5% performance increase on an IPsec test run
using pcrypt.

Btw. the seq_lock spinlock was never explicitly initialized -- one more
reason to get rid of it.

Signed-off-by: Mathias Krause <mathias.krause@secunet.com>
Acked-by: Steffen Klassert <steffen.klassert@secunet.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
This commit is contained in:
Mathias Krause 2013-10-25 12:14:15 +02:00 • committed by Herbert Xu
parent cfc6f11b76
commit 0b6b098efc
2 changed files with 5 additions and 7 deletions
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3
include/linux/padata.h
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@ -129,10 +129,9 @@ struct parallel_data {
struct padata_serial_queue __percpu *squeue;
atomic_t reorder_objects;
atomic_t refcnt;
atomic_t seq_nr;
struct padata_cpumask cpumask;
spinlock_t lock ____cacheline_aligned;
spinlock_t seq_lock;
unsigned int seq_nr;
unsigned int processed;
struct timer_list timer;
};