From: Ravikiran G Thirumalai <kiran@scalex86.org>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: linux-kernel@vger.kernel.org
Subject: [patch] Pad irq_desc to internode cacheline size
Date: Mon, 9 Apr 2007 12:56:27 -0700 [thread overview]
Message-ID: <20070409195356.GA5275@localhost.localdomain> (raw)
We noticed a drop in n/w performance due to the irq_desc being cacheline
aligned rather than internode aligned. We see 50% of expected performance
when two e1000 nics local to two different nodes have consecutive irq
descriptors allocated, due to false sharing.
Note that this patch does away with cacheline padding for the UP case, as it
does not seem useful for UP configurations.
Signed-off-by: Ravikiran Thirumalai <kiran@scalex86.org>
Signed-off-by: Shai Fultheim <shai@scalex86.org>
Index: linux-2.6.21-rc5/include/linux/irq.h
===================================================================
--- linux-2.6.21-rc5.orig/include/linux/irq.h 2007-04-09 10:16:23.560848473 -0700
+++ linux-2.6.21-rc5/include/linux/irq.h 2007-04-09 10:16:45.401177929 -0700
@@ -175,7 +175,7 @@ struct irq_desc {
struct proc_dir_entry *dir;
#endif
const char *name;
-} ____cacheline_aligned;
+} ____cacheline_internodealigned_in_smp;
extern struct irq_desc irq_desc[NR_IRQS];
Index: linux-2.6.21-rc5/kernel/irq/handle.c
===================================================================
--- linux-2.6.21-rc5.orig/kernel/irq/handle.c 2007-02-04 10:44:54.000000000 -0800
+++ linux-2.6.21-rc5/kernel/irq/handle.c 2007-04-09 12:26:40.473326023 -0700
@@ -48,7 +48,7 @@ handle_bad_irq(unsigned int irq, struct
*
* Controller mappings for all interrupt sources:
*/
-struct irq_desc irq_desc[NR_IRQS] __cacheline_aligned = {
+struct irq_desc irq_desc[NR_IRQS] __cacheline_aligned_in_smp = {
[0 ... NR_IRQS-1] = {
.status = IRQ_DISABLED,
.chip = &no_irq_chip,
next reply other threads:[~2007-04-09 20:39 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-04-09 19:56 Ravikiran G Thirumalai [this message]
2007-04-09 20:57 ` [patch] Pad irq_desc to internode cacheline size Andrew Morton
2007-04-09 21:47 ` Eric W. Biederman
2007-04-09 22:09 ` Ravikiran G Thirumalai
2007-04-09 22:33 ` Eric W. Biederman
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