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[59.102.83.192]) by smtp.gmail.com with ESMTPSA id r23-v6sm20392894pfj.5.2018.08.26.22.00.10 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Sun, 26 Aug 2018 22:00:16 -0700 (PDT) Date: Mon, 27 Aug 2018 15:00:08 +1000 From: Nicholas Piggin To: Peter Zijlstra Cc: Will Deacon , Linus Torvalds , Benjamin Herrenschmidt , Andrew Lutomirski , the arch/x86 maintainers , Borislav Petkov , Rik van Riel , Jann Horn , Adin Scannell , Dave Hansen , Linux Kernel Mailing List , linux-mm , David Miller , Martin Schwidefsky , Michael Ellerman Subject: Re: [PATCH 3/4] mm/tlb, x86/mm: Support invalidating TLB caches for RCU_TABLE_FREE Message-ID: <20180827150008.13bce08f@roar.ozlabs.ibm.com> In-Reply-To: <20180824113953.GL24142@hirez.programming.kicks-ass.net> References: <20180822153012.173508681@infradead.org> <20180822154046.823850812@infradead.org> <20180822155527.GF24124@hirez.programming.kicks-ass.net> <20180823134525.5f12b0d3@roar.ozlabs.ibm.com> <776104d4c8e4fc680004d69e3a4c2594b638b6d1.camel@au1.ibm.com> <20180823133958.GA1496@brain-police> <20180824084717.GK24124@hirez.programming.kicks-ass.net> <20180824113214.GK24142@hirez.programming.kicks-ass.net> <20180824113953.GL24142@hirez.programming.kicks-ass.net> X-Mailer: Claws Mail 3.17.0 (GTK+ 2.24.32; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 24 Aug 2018 13:39:53 +0200 Peter Zijlstra wrote: > On Fri, Aug 24, 2018 at 01:32:14PM +0200, Peter Zijlstra wrote: > > On Fri, Aug 24, 2018 at 10:47:17AM +0200, Peter Zijlstra wrote: > > > On Thu, Aug 23, 2018 at 02:39:59PM +0100, Will Deacon wrote: > > > > The only problem with this approach is that we've lost track of the granule > > > > size by the point we get to the tlb_flush(), so we can't adjust the stride of > > > > the TLB invalidations for huge mappings, which actually works nicely in the > > > > synchronous case (e.g. we perform a single invalidation for a 2MB mapping, > > > > rather than iterating over it at a 4k granule). > > > > > > > > One thing we could do is switch to synchronous mode if we detect a change in > > > > granule (i.e. treat it like a batch failure). > > > > > > We could use tlb_start_vma() to track that, I think. Shouldn't be too > > > hard. > > > > Hurm.. look at commit: > > > > e77b0852b551 ("mm/mmu_gather: track page size with mmu gather and force flush if page size change") > > Ah, good, it seems that already got cleaned up a lot. But it all moved > into the power code.. blergh. I lost track of what the problem is here? For powerpc, tlb_start_vma is not the right API to use for this because it wants to deal with different page sizes within a vma. Thanks, Nick