Messages in this thread | | | Date | Tue, 4 Jun 2019 18:07:35 +0800 | From | Feng Tang <> | Subject | Re: [LKP] [tcp] 8b27dae5a2: netperf.Throughput_Mbps -25.7% regression |
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On Thu, May 30, 2019 at 11:23:14PM +0800, Feng Tang wrote: > Hi Eric, > > On Thu, May 30, 2019 at 05:21:40AM -0700, Eric Dumazet wrote: > > On Thu, May 30, 2019 at 3:31 AM Feng Tang <feng.tang@intel.com> wrote: > > > > > > On Wed, Apr 03, 2019 at 02:34:36PM +0800, kernel test robot wrote: > > > > Greeting, > > > > > > > > FYI, we noticed a -25.7% regression of netperf.Throughput_Mbps due to commit: > > > > > > > > > > > > commit: 8b27dae5a2e89a61c46c6dbc76c040c0e6d0ed4c ("tcp: add one skb cache for rx") > > > > https://git.kernel.org/cgit/linux/kernel/git/next/linux-next.git master > > > > > > Hi Eric, > > > > > > Could you help to check this? thanks, > > > > > > > Hmmm... patch is old and had some bugs that have been fixed. > > > > What numbers do you have with more recent kernels ? > > > I just run the test with 5.2-rc2, and the regression is still there.
Hi Eric,
Any hint on this?
From the perf data, the spinlock contention has an obvious increase:
9.28 +7.6 16.91 perf-profile.calltrace.cycles-pp.native_queued_spin_lock_slowpath._raw_spin_lock.free_one_page.__free_pages_ok.___pskb_trim 18.55 +8.6 27.14 perf-profile.calltrace.cycles-pp.native_queued_spin_lock_slowpath._raw_spin_lock_irqsave.get_page_from_freelist.__alloc_pages_nodemask.skb_page_frag_refill
And for commit 8b27dae5a2 ("tcp: add one skb cache for rx"), IIUC, it is not a real cache like the "tx skb cache" patch, and kind of a delayed freeing.
Thanks, Feng
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