Messages in this thread | | | Date | Wed, 26 Sep 2012 19:15:41 +0200 | From | Borislav Petkov <> | Subject | Re: 20% performance drop on PostgreSQL 9.2 from kernel 3.5.3 to 3.6-rc5 on AMD chipsets - bisected |
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On Tue, Sep 25, 2012 at 07:22:22PM -0700, Linus Torvalds wrote: > So I'm sure there are architecture differences (where HT in particular > probably changes optimal scheduling strategy, although I'd expect > the bulldozer approach to not be *that*different - but I don't know > if BD shows up as "HT siblings" or not, so dissimilar topology > interpretation may make it *look* very different).
Right, those cores sharing an L2 are thread siblings on BD:
$ grep . /sys/devices/system/cpu/cpu0/topology/* /sys/devices/system/cpu/cpu0/topology/core_id:0 /sys/devices/system/cpu/cpu0/topology/core_siblings:ff /sys/devices/system/cpu/cpu0/topology/core_siblings_list:0-7 /sys/devices/system/cpu/cpu0/topology/physical_package_id:0 /sys/devices/system/cpu/cpu0/topology/thread_siblings:03 /sys/devices/system/cpu/cpu0/topology/thread_siblings_list:0-1
much like HT siblings on this single-socket Sandybridge:
$ grep . /sys/devices/system/cpu/cpu0/topology/* /sys/devices/system/cpu/cpu0/topology/core_id:0 /sys/devices/system/cpu/cpu0/topology/core_siblings:ff /sys/devices/system/cpu/cpu0/topology/core_siblings_list:0-7 /sys/devices/system/cpu/cpu0/topology/physical_package_id:0 /sys/devices/system/cpu/cpu0/topology/thread_siblings:11 /sys/devices/system/cpu/cpu0/topology/thread_siblings_list:0,4
Although I don't know whether those thread siblings on this SB box are actual HT siblings, sharing almost all resources, judging by the core ids.
-- Regards/Gruss, Boris.
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