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From: Andi Kleen <ak@suse.de>
To: "Bryan O'Sullivan" <bos@pathscale.com>, Andi Kleen <ak@suse.de>,
	Roland Dreier <rolandd@cisco.com>,
	patches@x86-64.org, linux-kernel@vger.kernel.org
Subject: [PATCH 2.6.21 review I] [22/25] x86_64: use memcpy_uncached_read() in RDMA interrupt handler to reduce packet loss
Date: Sat, 10 Feb 2007 12:50:35 +0100 (CET)	[thread overview]
Message-ID: <20070210115035.7683213DCE@wotan.suse.de> (raw)
In-Reply-To: <200702101250.142420000@suse.de>


From: "Bryan O'Sullivan" <bos@pathscale.com>

In cases where a large incoming RDMA is being received, we have to copy data
inside the interrupt handler before we can ACK each packet.  The source is
DMAed to by the hardware, which means that the CPU won't have it cached.  We
only read the source this one time; using normal load instructions pollutes
the dcache with useless data, reducing performance to the point where we can
lose a significant number of packets.

We use memcpy_uncached_read to try to not fill the dcache with useless data. 
Avoiding the cache refill penalty lets us keep up better with the sender,
resulting in many fewer dropped packets.

Signed-off-by: Bryan O'Sullivan <bryan.osullivan@qlogic.com>
Signed-off-by: Andi Kleen <ak@suse.de>
Cc: Andi Kleen <ak@suse.de>
Cc: Roland Dreier <rolandd@cisco.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
---

 drivers/infiniband/hw/ipath/ipath_verbs.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Index: linux/drivers/infiniband/hw/ipath/ipath_verbs.c
===================================================================
--- linux.orig/drivers/infiniband/hw/ipath/ipath_verbs.c
+++ linux/drivers/infiniband/hw/ipath/ipath_verbs.c
@@ -167,7 +167,7 @@ void ipath_copy_sge(struct ipath_sge_sta
 		BUG_ON(len == 0);
 		if (len > length)
 			len = length;
-		memcpy(sge->vaddr, data, len);
+		memcpy_uncached_read(sge->vaddr, data, len);
 		sge->vaddr += len;
 		sge->length -= len;
 		sge->sge_length -= len;

  parent reply	other threads:[~2007-02-10 12:01 UTC|newest]

Thread overview: 38+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2007-02-10 11:50 [PATCH 2.6.21 review I] [1/25] x86_64: Add __copy_from_user_nocache Andi Kleen
2007-02-10 11:50 ` [PATCH 2.6.21 review I] [2/25] x86_64: Make the NUMA hash function nodemap allocation Andi Kleen
2007-02-10 11:50 ` [PATCH 2.6.21 review I] [3/25] i386: Convert i386 PDA code to use %fs Andi Kleen
2007-02-10 11:50 ` [PATCH 2.6.21 review I] [4/25] x86: kernel-mode faults pollute current->thead Andi Kleen
2007-02-12  9:32   ` [patches] " Jan Beulich
2007-02-12 16:42     ` Jeff Dike
2007-02-12 17:01       ` Jan Beulich
2007-02-10 11:50 ` [PATCH 2.6.21 review I] [5/25] i386: revert i386-fix-the-verify_quirk_intel_irqbalance Andi Kleen
2007-02-10 11:50 ` [PATCH 2.6.21 review I] [6/25] x86_64: revert x86_64-mm-add-genapic_force Andi Kleen
2007-02-10 11:50 ` [PATCH 2.6.21 review I] [7/25] x86: revert x86_64-mm-fix-the-irqbalance-quirk-for-e7320-e7520-e7525 Andi Kleen
2007-02-10 11:50 ` [PATCH 2.6.21 review I] [8/25] x86_64: optimize & fix APIC mode setup Andi Kleen
2007-02-10 11:50 ` [PATCH 2.6.21 review I] [9/25] x86_64: always use physical delivery mode on > 8 CPUs Andi Kleen
2007-02-10 11:50 ` [PATCH 2.6.21 review I] [10/25] x86_64: remove clustered APIC mode Andi Kleen
2007-02-10 11:50 ` [PATCH 2.6.21 review I] [11/25] x86: default to physical mode on hotplug CPU kernels Andi Kleen
2007-02-11 11:13   ` Eric W. Biederman
2007-02-12 22:36     ` Andi Kleen
2007-02-12 23:10       ` Eric W. Biederman
2007-02-12 23:51         ` Siddha, Suresh B
2007-02-12 23:43       ` Siddha, Suresh B
2007-02-10 11:50 ` [PATCH 2.6.21 review I] [12/25] x86_64: x86_64-make-the-numa-hash-function-nodemap-allocation fix fix Andi Kleen
2007-02-10 11:50 ` [PATCH 2.6.21 review I] [13/25] i386: Fix a typo in an IRQ handler name Andi Kleen
2007-02-10 11:50 ` [PATCH 2.6.21 review I] [14/25] x86: Share what's shareable Andi Kleen
2007-02-10 11:50 ` [PATCH 2.6.21 review I] [15/25] i386: Only call unreachable_devices() when type 1 is available Andi Kleen
2007-02-10 11:50 ` [PATCH 2.6.21 review I] [16/25] i386: Detect and support the E7520 and the 945G/GZ/P/PL Andi Kleen
2007-02-10 11:50 ` [PATCH 2.6.21 review I] [17/25] i386: Reserve resources but only when we're sure about them Andi Kleen
2007-02-10 11:50 ` [PATCH 2.6.21 review I] [18/25] x86_64: Fix x86_64 ioremap base_address Andi Kleen
2007-02-10 11:58   ` Arjan van de Ven
2007-02-10 12:07     ` Andi Kleen
2007-02-10 11:50 ` [PATCH 2.6.21 review I] [19/25] x86: Reject a broken MCFG tables on Asus etc Andi Kleen
2007-02-10 11:50 ` [PATCH 2.6.21 review I] [20/25] x86_64: get rid of ARCH_HAVE_XTIME_LOCK Andi Kleen
2007-02-10 11:50 ` [PATCH 2.6.21 review I] [21/25] x86_64: a memcpy that tries to reduce cache pressure Andi Kleen
2007-02-12  9:57   ` [patches] " Jan Beulich
2007-02-12 10:25     ` Andi Kleen
2007-02-13 11:27   ` Eric Dumazet
2007-02-10 11:50 ` Andi Kleen [this message]
2007-02-10 11:50 ` [PATCH 2.6.21 review I] [23/25] x86_64: improved iommu documentation Andi Kleen
2007-02-10 11:50 ` [PATCH 2.6.21 review I] [24/25] x86_64: do not always end the stack trace with ULONG_MAX Andi Kleen
2007-02-10 11:50 ` [PATCH 2.6.21 review I] [25/25] i386: arch/i386/kernel/e820.c should #include <asm/setup.h Andi Kleen

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