From mboxrd@z Thu Jan  1 00:00:00 1970
From: Christian Borntraeger <borntraeger@de.ibm.com>
Subject: Re: [RFC]Two ideas to optimize updating irq routing table
Date: Wed, 26 Mar 2014 12:14:34 +0100
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References: <33183CC9F5247A488A2544077AF19020815DA9BD@SZXEMA503-MBS.china.huawei.com> <53317892.2050506@redhat.com> <33183CC9F5247A488A2544077AF19020815DAEBA@SZXEMA503-MBS.china.huawei.com>
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Cc: "gleb@redhat.com" <gleb@redhat.com>,
	"mst@redhat.com" <mst@redhat.com>,
	"avi.kivity@gmail.com" <avi.kivity@gmail.com>,
	"Herongguang (Stephen)" <herongguang.he@huawei.com>,
	"Huangweidong (C)" <weidong.huang@huawei.com>
To: "Gonglei (Arei)" <arei.gonglei@huawei.com>,
	Paolo Bonzini <pbonzini@redhat.com>,
	"qemu-devel@nongnu.org" <qemu-devel@nongnu.org>,
	"kvm@vger.kernel.org" <kvm@vger.kernel.org>
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On 26/03/14 09:22, Gonglei (Arei) wrote:

> Without patches, ping time can jump from 0.3ms to 2ms-30ms. With synchronize_srcu 
> patch, ping time is worse. With synchronize_srcu_expedited patch, ping time is 
> overall good, though sometimes ping time jump to 1ms-3ms.

Just to understand whats going on, does something like

diff --git a/kernel/rcu/srcu.c b/kernel/rcu/srcu.c
index 3318d82..432c2a2 100644
--- a/kernel/rcu/srcu.c
+++ b/kernel/rcu/srcu.c
@@ -331,7 +331,7 @@ EXPORT_SYMBOL_GPL(__srcu_read_unlock);
  */
 #define SRCU_RETRY_CHECK_DELAY         5
 #define SYNCHRONIZE_SRCU_TRYCOUNT      2
-#define SYNCHRONIZE_SRCU_EXP_TRYCOUNT  12
+#define SYNCHRONIZE_SRCU_EXP_TRYCOUNT  50
 
 /*
  * @@@ Wait until all pre-existing readers complete.  Such readers

make the problem go away?