From: Stephen Hemminger <shemminger@xxxxxxxx>
Date: Thu, 9 Jun 2005 15:05:46 -0700
> > I have profile data, here is an example of 5tx/5rx threads, where the
> > throughput was 1236Mb/s total, 936tx, 300rx, on 2.6.12-rc5 with old TSO
> > (the original problem case) we are at 100% cpu and generating 3289 ints/s,
> > with no hardware drops reported prolly due to my replenish patch
> > CPU: P4 / Xeon with 2 hyper-threads, speed 2791.36 MHz (estimated)
> > Counted GLOBAL_POWER_EVENTS events (time during which processor is not
> > stopped) with a unit mask of 0x01 (mandatory) count 100000
> > samples % image name symbol name
> > 533687 8.1472 vmlinux pskb_expand_head
> > 428726 6.5449 vmlinux __copy_user_zeroing_intel
> > 349934 5.3421 vmlinux _read_lock_irqsave
>
> We should kill all reader/writer locks in the fastpath. reader locks are
> more expensive than spinlocks unless they are going to be held for a fairly
> large window.
True, but I see no reason why it should have any influence here.
Let's not get distracted by this in our analysis of the problem.
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