From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id BDE91493632 for ; Wed, 2 Sep 2026 13:16:44 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788355005; cv=none; b=rqWx4zs7fVEkk9euRToI0tAnl+wjeYs+ZXnxDnSMA7S4hISW+0vQA9eVbIjWmk1cSHx1gvfxy+5lpJRc4vvEpYA/h5X+tsFy9VOzD2CYgK/2l5EeV+B0+oTW86+WnuSbFrgJLE/5pLZz61PCuX5xfUI76zhQrm9Lrqx+PTSEvQY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788355005; c=relaxed/simple; bh=PIeNSn6dbPUSzotuL6dJrll2mRcEyuhJ+Z+5qYBburs=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=aLYAnIKaI7wALpnVbbhxctldbs1CBacQliaWYhF7N8y91gUzvdAw6DWPgsIp9Bf3LvmrQ+ByDp3gBH9v9hXMbLuAmUj2qfoDTQA2hHOTNtFBSc335/wApIpyOdxdNRleZLGphs8Wlcg4tJ7wZkpdfLh4hvl1PtfoKmfC/MV8ueA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=C9SE43wk; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="C9SE43wk" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 8E31C1F000E9; Wed, 2 Sep 2026 13:16:40 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1788355004; bh=WHyZ/G63rvwAjwU4vztYef/xCH4xZmisnZYFznJHchw=; h=Date:From:To:Cc:Subject:References:In-Reply-To; b=C9SE43wk6wEfvY7rbwjJlIDhxPYF4V8mY5JBn8DHaeqItWWDBLmp5vfg6hVeFPmJt 0rarlD9cqaUHCpo2jYgIre0ly39rkiyJVv04hOyUlEV8OzUqniAlwi5s03flzFPLeK lcojVVMmP5puGAJCTODq+wkeRSozRKVFNTVtVc2tj0gEMWlQaHFixWF8jtbXPZAYij EsMvyzQiykJq5mP7pf+Prr9jhVQsFoafmFQsKMd95VtikdmAY2TBAKa7M4p3XbJRzC dKoGPdG4g1bRVpAngjdCXe4UZJMLIgdG5GL3qiJZZOyOvPJbYqs7HPKMg2n2dgMfYe ePcvcMLfslAew== Date: Wed, 2 Sep 2026 14:16:37 +0100 From: "Lorenzo Stoakes (ARM)" To: Usama Anjum Cc: Mark Rutland , linux-arm-kernel@lists.infradead.org, vladimir.murzin@arm.com, ryan.roberts@arm.com, peterz@infradead.org, catalin.marinas@arm.com, david.laight.linux@gmail.com, stable@vger.kernel.org, ruanjinjie@huawei.com, james.morse@arm.com, yang@os.amperecomputing.com, cl@gentwo.org, maz@kernel.org, david@kernel.org, will@kernel.org, ardb@kernel.org Subject: Re: [PATCH v2 00/20] arm64: Preemptible this_cpu_*() operations Message-ID: References: <20260804170503.3513916-1-mark.rutland@arm.com> <9789fd67-205a-412f-90d6-42c401d3babe@arm.com> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <9789fd67-205a-412f-90d6-42c401d3babe@arm.com> On Wed, Sep 02, 2026 at 12:55:12PM +0100, Usama Anjum wrote: > tl;dr > Comparing this series with the page-table series [a] gives 8 improvements and 3 > regressions. And the regressions are very small and importantly the improvements that presumably form the basis of doing any of this at all (i.e. munmap, vmalloc) perform _better_ with Mark's series, without requiring egregious core mm changes + complexity. > > Fastpath is a Linux kernel performance benchmarking service. The table > compares the both patched kernels: positive values are faster, negative > values are slower, and (I)/(R) indicate statistically significant > improvements/regressions. Unmarked differences are not significant after > accounting for confidence and noise thresholds. > > +---------------------------------+--------------------+-----------------+-----------------------+ > | Benchmark | percpu-pgtable [2] | gpr-fixup [3] | gpr-fixup [3] | > | | vs baseline [1] | vs baseline [1] | vs percpu-pgtable [2] | > +=================================+====================+=================+=======================+ > | lmbench/lat-mem-rd | -0.26% | (I) 1.24% | (I) 1.50% | > | micromm/fork | (I) 1.10% | (I) 2.46% | (I) 1.35% | > | micromm/munmap | (I) 18.10% | (I) 19.78% | (I) 1.43% | > | micromm/vmalloc | (I) 11.92% | (I) 14.68% | (I) 2.47% | > | mmtests/hackbench | 0.27% | (I) 1.09% | 0.81% | > | mmtests/kernbench | (I) 1.19% | (I) 1.18% | -0.01% | > | mmtests/sysbench-cpu | 0.01% | 0.06% | 0.05% | > | mmtests/sysbench-mutex | -0.85% | -0.14% | 0.72% | > | mmtests/sysbench-thread | (R) -4.49% | (I) 3.02% | (I) 7.86% | > | perf/futex | 0.55% | (R) -2.80% | (R) -3.34% | > | perf/sched | (I) 1.61% | -0.39% | (R) -1.97% | > | perf/syscall | (I) 1.54% | 0.98% | -0.55% | > | pts/memtier-benchmark | (I) 2.37% | (I) 2.51% | 0.14% | > | pts/nginx | 0.42% | 0.96% | 0.54% | > | pts/perl-benchmark | (I) 1.83% | (I) 1.63% | -0.20% | > | pts/pgbench | -0.09% | 0.55% | 0.65% | > | pts/pybench | -0.05% | -0.07% | -0.02% | > | pts/redis | -0.00% | -0.04% | -0.04% | > | pts/sqlite-speedtest | 0.15% | 0.44% | 0.28% | > | repro-collection/mysql-workload | 0.73% | 0.25% | -0.48% | > | schbench/thread-contention | 0.42% | (I) 1.04% | 0.61% | > | sockperf/echo-lat-tcp | (I) 2.88% | (I) 1.69% | (R) -1.16% | > | sockperf/echo-lat-udp | (I) 3.93% | (I) 5.11% | (I) 1.14% | > | sockperf/packet-tp-tcp | -0.41% | (I) 1.37% | (I) 1.79% | > | sockperf/packet-tp-udp | (I) 1.45% | (I) 1.49% | 0.04% | > | specjbb/composite | (I) 1.39% | (I) 1.65% | 0.26% | > | speedometer/v2.0 | (R) -1.04% | (R) -1.04% | 0.00% | > | speedometer/v2.1 | -0.10% | 0.10% | 0.20% | > | syscall/getpid | -0.98% | 0.52% | (I) 1.51% | > | syscall/getppid | -0.43% | 0.14% | 0.57% | > | syscall/invalid | (I) 3.06% | (I) 3.56% | 0.48% | > +---------------------------------+--------------------+-----------------+-----------------------+ Lovely :) Well that settles the debate then! -- Cheers, Lorenzo