netdev - Re: [PATCH v2 net-next] af_unix: reduce high order page allocations

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Date:	Tue, 03 Apr 2012 16:43:52 -0400 (EDT)
From:	David Miller <davem@...emloft.net>
To:	eric.dumazet@...il.com
Cc:	netdev@...r.kernel.org
Subject: Re: [PATCH v2 net-next] af_unix: reduce high order page allocations

From: Eric Dumazet <eric.dumazet@...il.com>
Date: Tue, 03 Apr 2012 17:28:28 +0200

> unix_dgram_sendmsg() currently builds linear skbs, and this can stress
> page allocator with high order page allocations. When memory gets
> fragmented, this can eventually fail.
> 
> We can try to use order-2 allocations for skb head (SKB_MAX_ALLOC) plus
> up to 16 page fragments to lower pressure on buddy allocator.
> 
> This patch has no effect on messages of less than 16064 bytes.
> (on 64bit arches with PAGE_SIZE=4096)
> 
> For bigger messages (from 16065 to 81600 bytes), this patch brings
> reliability at the expense of performance penalty because of extra pages
> allocations.
> 
> netperf -t DG_STREAM -T 0,2 -- -m 16064 -s 200000
> ->4086040 Messages / 10s
> 
> netperf -t DG_STREAM -T 0,2 -- -m 16068 -s 200000
> ->3901747 Messages / 10s
> 
> Signed-off-by: Eric Dumazet <eric.dumazet@...il.com>
> ---
> v2: use SKB_MAX_ALLOC instead of SKB_MAX_ORDER(0, 0) to not slow down
>     applications using up to 16000 bytes messages.

Looks good, applied to net-next, thanks Eric!
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