netdev - Re: surprising memory request

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Date:	Fri, 18 Jan 2013 09:54:33 -0800
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Dirk Hohndel <dirk@...ndel.org>
Cc:	Jason Wang <jasowang@...hat.com>, netdev@...r.kernel.org,
	David Woodhouse <dwmw2@...radead.org>
Subject: Re: surprising memory request

On Fri, 2013-01-18 at 09:46 -0800, Eric Dumazet wrote:

> Thats because Jason thought that tun device had to have an insane number
> of queues to get good performance.
> 
> #define MAX_TAP_QUEUES 1024
> 
> Thats crazy if your machine has say 8 cpus.
> 
> And Jason didnt care to adapt the memory allocations done in
> alloc_netdev_mqs(), in order to switch to vmalloc() when kmalloc()
> fails.

I suggest using the more reasonable :

diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index c81680d..ec18fbf 100644
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -113,7 +113,7 @@ struct tap_filter {
  * the order of 100-200 CPUs so this leaves us some breathing space if we want
  * to match a queue per guest CPU.
  */
-#define MAX_TAP_QUEUES 1024
+#define MAX_TAP_QUEUES DEFAULT_MAX_NUM_RSS_QUEUES
 
 #define TUN_FLOW_EXPIRE (3 * HZ)
 


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