Messages in this thread | | | Date | Thu, 09 Jan 2014 15:00:51 -0500 | From | Rik van Riel <> | Subject | Re: [PATCH 5/5] mm: x86: Revisit tlb_flushall_shift tuning for page flushes except on IvyBridge |
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On 01/09/2014 09:34 AM, Mel Gorman wrote: > There was a large ebizzy performance regression that was bisected to commit > 611ae8e3 (x86/tlb: enable tlb flush range support for x86). The problem > was related to the tlb_flushall_shift tuning for IvyBridge which was > altered. The problem is that it is not clear if the tuning values for each > CPU family is correct as the methodology used to tune the values is unclear. > > This patch uses a conservative tlb_flushall_shift value for all CPU families > except IvyBridge so the decision can be revisited if any regression is found > as a result of this change. IvyBridge is an exception as testing with one > methodology determined that the value of 2 is acceptable. Details are in the > changelog for the patch "x86: mm: Change tlb_flushall_shift for IvyBridge". > > One important aspect of this to watch out for is Xen. The original commit > log mentioned large performance gains on Xen. It's possible Xen is more > sensitive to this value if it flushes small ranges of pages more frequently > than workloads on bare metal typically do. > > Signed-off-by: Mel Gorman <mgorman@suse.de>
Reviewed-by: Rik van Riel <riel@redhat.com>
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