Re: hackbench regression due to commit 9dfc6e68bfe6e
From: Zhang, Yanmin
Date: Fri Apr 02 2010 - 04:05:23 EST
On Thu, 2010-04-01 at 10:53 -0500, Christoph Lameter wrote:
> On Thu, 1 Apr 2010, Zhang, Yanmin wrote:
> > I suspect the moving of place of cpu_slab in kmem_cache causes the new cache
> > miss. But when I move it to the tail of the structure, kernel always panic when
> > booting. Perhaps there is another potential bug?
> Why would that cause an additional cache miss?
> The node array is following at the end of the structure. If you want to
> move it down then it needs to be placed before the node field
Thanks. The moving cpu_slab to tail doesn't improve it.
I used perf to collect statistics. Only data cache miss has a little difference.
My testing command on my 2 socket machine:
#hackbench 100 process 20000
With 2.6.33, it takes for about 96 seconds while 2.6.34-rc2 (or the latest tip tree)
takes for about 101 seconds.
perf shows some functions around SLUB have more cpu utilization, while some other
SLUB functions have less cpu utilization.
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/