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[198.145.64.163]) by smtp.gmail.com with ESMTPSA id a23sm3234684pfo.80.2019.08.28.10.36.24 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 28 Aug 2019 10:36:29 -0700 (PDT) Date: Tue, 27 Aug 2019 10:51:59 -0700 From: Kees Cook To: Will Deacon Cc: linux-kernel@vger.kernel.org, Ingo Molnar , Elena Reshetova , Peter Zijlstra , Ard Biesheuvel , Hanjun Guo , Jan Glauber Subject: Re: [PATCH v2 0/6] Rework REFCOUNT_FULL using atomic_fetch_* operations Message-ID: <201908271051.5B9C9F25@keescook> References: <20190827163204.29903-1-will@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190827163204.29903-1-will@kernel.org> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Aug 27, 2019 at 05:31:58PM +0100, Will Deacon wrote: > Hi all, > > This is version two of the patches I previously posted here: > > https://lkml.kernel.org/r/20190802101000.12958-1-will@kernel.org > > Changes since v1 include: > > * Avoid duplicate WARNs when incrementing from zero > * Some crude lktdm perf results to motivate the change: > > # perf stat -r 3 -B -- echo {ATOMIC,REFCOUNT}_TIMING >/sys/kernel/debug/provoke-crash/DIRECT > > # arm64 > ATOMIC_TIMING: 46.50451 +- 0.00134 seconds time elapsed ( +- 0.00% ) > REFCOUNT_TIMING (REFCOUNT_FULL, mainline): 77.57522 +- 0.00982 seconds time elapsed ( +- 0.01% ) > REFCOUNT_TIMING (REFCOUNT_FULL, this series): 48.7181 +- 0.0256 seconds time elapsed ( +- 0.05% ) > > # x86 > ATOMIC_TIMING: 31.6225 +- 0.0776 seconds time elapsed ( +- 0.25% ) > REFCOUNT_TIMING (!REFCOUNT_FULL, mainline/x86 asm): 31.6689 +- 0.0901 seconds time elapsed ( +- 0.28% ) > REFCOUNT_TIMING (REFCOUNT_FULL, mainline): 53.203 +- 0.138 seconds time elapsed ( +- 0.26% ) > REFCOUNT_TIMING (REFCOUNT_FULL, this series): 31.7408 +- 0.0486 seconds time elapsed ( +- 0.15% ) Nice improvements! :) Please consider the series: Reviewed-by: Kees Cook -Kees > > Cheers, > > Will > > Cc: Kees Cook > Cc: Ingo Molnar > Cc: Elena Reshetova > Cc: Peter Zijlstra > Cc: Ard Biesheuvel > Cc: Hanjun Guo > Cc: Jan Glauber > > --->8 > > Will Deacon (6): > lib/refcount: Define constants for saturation and max refcount values > lib/refcount: Ensure integer operands are treated as signed > lib/refcount: Remove unused refcount_*_checked() variants > lib/refcount: Move bulk of REFCOUNT_FULL implementation into header > lib/refcount: Improve performance of generic REFCOUNT_FULL code > lib/refcount: Consolidate REFCOUNT_{MAX,SATURATED} definitions > > drivers/misc/lkdtm/refcount.c | 8 -- > include/linux/refcount.h | 236 +++++++++++++++++++++++++++++++++++++---- > lib/refcount.c | 237 +----------------------------------------- > 3 files changed, 218 insertions(+), 263 deletions(-) > > -- > 2.11.0 > -- Kees Cook