From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pg0-x243.google.com (mail-pg0-x243.google.com [IPv6:2607:f8b0:400e:c05::243]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 3yRq8w0pWrzDr4H for ; Thu, 2 Nov 2017 00:40:15 +1100 (AEDT) Received: by mail-pg0-x243.google.com with SMTP id g6so2146588pgn.6 for ; Wed, 01 Nov 2017 06:40:15 -0700 (PDT) Date: Thu, 2 Nov 2017 00:39:56 +1100 From: Nicholas Piggin To: Anshuman Khandual Cc: linuxppc-dev@lists.ozlabs.org, "Aneesh Kumar K . V" Subject: Re: [RFC PATCH 0/7] powerpc/64s/radix TLB flush performance improvements Message-ID: <20171102003956.6cbeded3@roar.ozlabs.ibm.com> In-Reply-To: References: <20171031064504.25245-1-npiggin@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Wed, 1 Nov 2017 17:35:51 +0530 Anshuman Khandual wrote: > On 10/31/2017 12:14 PM, Nicholas Piggin wrote: > > Here's a random mix of performance improvements for radix TLB flushing > > code. The main aims are to reduce the amount of translation that gets > > invalidated, and to reduce global flushes where we can do local. > > > > To that end, a parallel kernel compile benchmark using powerpc:tlbie > > tracepoint shows a reduction in tlbie instructions from about 290,000 > > to 80,000, and a reduction in tlbiel instructions from 49,500,000 to > > 15,000,000. Looks great, but unfortunately does not translate to a > > statistically significant performance improvement! The needle on TLB > > misses does not move much, I suspect because a lot of the flushing is > > done a startup and shutdown, and because a significant cost of TLB > > flushing itself is in the barriers. > > Does memory barrier initiate a single global invalidation with tlbie ? > I'm not quite sure what you're asking, and I don't know the details of how the hardware handles it, but from the measurements in patch 1 of the series we can see there is a benefit for both tlbie and tlbiel of batching them up between barriers. Thanks, Nick