On 06/19/2013 02:31 PM, Eric Dumazet wrote:
> On Wed, 2013-06-19 at 13:40 +0800, Jason Wang wrote:
>> Currently, we use kcalloc to allocate rx/tx queues for a net device which
>> could
>> be easily lead to a high order memory allocation request when initializing a
>> multiqueue net device. We can simply avoid this by switching to use flex
>> array
>> which always allocate at order zero.
>>
>> Signed-off-by: Jason Wang <jasow...@redhat.com>
>> ---
>> include/linux/netdevice.h | 13 ++++++----
>> net/core/dev.c | 57
>> ++++++++++++++++++++++++++++++++------------
>> net/core/net-sysfs.c | 15 +++++++----
>> 3 files changed, 58 insertions(+), 27 deletions(-)
>>
>> diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
>> index 09b4188..c0b5d04 100644
>> --- a/include/linux/netdevice.h
>> +++ b/include/linux/netdevice.h
>> @@ -32,6 +32,7 @@
>> #include <linux/atomic.h>
>> #include <asm/cache.h>
>> #include <asm/byteorder.h>
>> +#include <linux/flex_array.h>
>>
>> #include <linux/percpu.h>
>> #include <linux/rculist.h>
>> @@ -1230,7 +1231,7 @@ struct net_device {
>>
>>
>> #ifdef CONFIG_RPS
>> - struct netdev_rx_queue *_rx;
>> + struct flex_array *_rx;
>>
>> /* Number of RX queues allocated at register_netdev() time */
>> unsigned int num_rx_queues;
>> @@ -1250,7 +1251,7 @@ struct net_device {
>> /*
>> * Cache lines mostly used on transmit path
>> */
>> - struct netdev_queue *_tx ____cacheline_aligned_in_smp;
>> + struct flex_array *_tx ____cacheline_aligned_in_smp;
>>
> Using flex_array and adding overhead in this super critical part of
> network stack, only to avoid order-1 allocations done in GFP_KERNEL
> context is simply insane.
Yes, and I also miss the fact of GFP_KERNEL allocation.
> We can revisit this in 2050 if we ever need order-4 allocations or so,
> and still use 4K pages.
>
>
Will drop this patch, thanks.
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