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Shutemov" To: Peter Zijlstra Cc: Dave Hansen , Andy Lutomirski , x86@kernel.org, Kostya Serebryany , Andrey Ryabinin , Andrey Konovalov , Alexander Potapenko , Taras Madan , Dmitry Vyukov , "H . J . Lu" , Andi Kleen , Rick Edgecombe , Bharata B Rao , Jacob Pan , Ashok Raj , Linus Torvalds , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCHv14 08/17] x86/mm: Reduce untagged_addr() overhead until the first LAM user Message-ID: <20230117135703.voaumisreld7crfb@box> References: <20230111123736.20025-1-kirill.shutemov@linux.intel.com> <20230111123736.20025-9-kirill.shutemov@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Stat-Signature: xje6nruf1igm7hx61paj11hxocdg5gh1 X-Rspam-User: X-Rspamd-Queue-Id: 15DAE100016 X-Rspamd-Server: rspam06 X-HE-Tag: 1673963838-143841 X-HE-Meta: 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 4ZA== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Tue, Jan 17, 2023 at 02:05:22PM +0100, Peter Zijlstra wrote: > On Wed, Jan 11, 2023 at 03:37:27PM +0300, Kirill A. Shutemov wrote: > > > #define __untagged_addr(untag_mask, addr) > > u64 __addr = (__force u64)(addr); \ > > - s64 sign = (s64)__addr >> 63; \ > > - __addr &= untag_mask | sign; \ > > + if (static_branch_likely(&tagged_addr_key)) { \ > > + s64 sign = (s64)__addr >> 63; \ > > + __addr &= untag_mask | sign; \ > > + } \ > > (__force __typeof__(addr))__addr; \ > > }) > > > > #define untagged_addr(addr) __untagged_addr(current_untag_mask(), addr) > > Is the compiler clever enough to put the memop inside the branch? Hm. You mean current_untag_mask() inside static_branch_likely()? But it is preprocessor who does this, not compiler. So, yes, the memop is inside the branch. Or I didn't understand your question. -- Kiryl Shutsemau / Kirill A. Shutemov