From patchwork Fri Jun 2 16:09:14 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Vipin Sharma X-Patchwork-Id: 13265619 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1C494C7EE2A for ; Fri, 2 Jun 2023 16:11:22 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236888AbjFBQLS (ORCPT ); Fri, 2 Jun 2023 12:11:18 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:36190 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236801AbjFBQK6 (ORCPT ); Fri, 2 Jun 2023 12:10:58 -0400 Received: from mail-pf1-x44a.google.com (mail-pf1-x44a.google.com [IPv6:2607:f8b0:4864:20::44a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 0E8951B9 for ; Fri, 2 Jun 2023 09:10:13 -0700 (PDT) Received: by mail-pf1-x44a.google.com with SMTP id d2e1a72fcca58-65320a6e904so380505b3a.0 for ; Fri, 02 Jun 2023 09:10:13 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20221208; t=1685722192; x=1688314192; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=pnaTvciscS5chSJrFdy/XWmGw+v5DL+sKG313yn6vtE=; b=3qM+gPLnKOcFkte53nrFJ4yxYHfRvj6VAQ74elJ+qIzLMj97WYlQnMm+LRqHDvoho4 8AW7RUIjuOvTDqJRc6MGpLfknZTHUVt0ac+jf1e4fznmqTNQB1YeAez2Pbf+vu4gX/wo xA9uw3YiFJ59xCiKuG3PqvgkOpwn1kfOyfDGnV3P6/41gfMjzqB9OHhb0wbZKNfck3ux QuubqPWPIMr2dr+usJ/0oHW/nWAg0PkVCfHTFjYBlz4FbohVSt4JZLXej+/lCcVIkw51 dikq26nIlv8414HoG8qlckcW0gk8fed5eU7B/bJPELllDOCa6K4cYwpu/yZBPdgX/sdW NMYg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1685722192; x=1688314192; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=pnaTvciscS5chSJrFdy/XWmGw+v5DL+sKG313yn6vtE=; b=jxMR3giG8YuG0eU5fWsIjrze72HtzoTTZgYra1OH5A4K4kG0rnJ9QKaAPApjqNDbli NfLUfPAE4I75QDxbmZ8jbsDHgxPeXB91l4qq/A77YxdejWD4yVUdWV2d80TJO62N6ZTh 5awCQxMSqUzd13cI6acseVEJ+3/9icopTqqetayS8ga6oC8HGOskOfQfCyZ1yo3HJiNr QZEUhFVR1frhydK3ELANy6xuquWjall2aB156RffDt/KBiDlltjZ6iX9sXL/c8IYdz+N uX0pvj/672+d9E6U5Atu7HEBPnBCuxDolHaSmZyBgEnIsO33RE9wD41FQjHCizo6r+0Z fzkA== X-Gm-Message-State: AC+VfDznuGjcJ5BSFmNhkUirf4na0CF/uxdhPYVXc1cJc/hdOh8ZyKhI cTKk2Xx+1CJiOA4Ig5A3BTrlzhOk0d3d X-Google-Smtp-Source: ACHHUZ7CrgQcXBBk0scZtBwPutYqwQ0i1jeHWFv03iHedZStcHfAHgjqtsGQJinldbGkFtIY3nwdqwhDBsPu X-Received: from vipin.c.googlers.com ([fda3:e722:ac3:cc00:7f:e700:c0a8:479f]) (user=vipinsh job=sendgmr) by 2002:a05:6a00:2e1a:b0:64f:9e1b:d4a8 with SMTP id fc26-20020a056a002e1a00b0064f9e1bd4a8mr4922796pfb.1.1685722192061; Fri, 02 Jun 2023 09:09:52 -0700 (PDT) Date: Fri, 2 Jun 2023 09:09:14 -0700 In-Reply-To: <20230602160914.4011728-1-vipinsh@google.com> Mime-Version: 1.0 References: <20230602160914.4011728-1-vipinsh@google.com> X-Mailer: git-send-email 2.41.0.rc0.172.g3f132b7071-goog Message-ID: <20230602160914.4011728-17-vipinsh@google.com> Subject: [PATCH v2 16/16] KVM: arm64: Split huge pages during clear-dirty-log under MMU read lock From: Vipin Sharma To: maz@kernel.org, oliver.upton@linux.dev, james.morse@arm.com, suzuki.poulose@arm.com, yuzenghui@huawei.com, catalin.marinas@arm.com, will@kernel.org, chenhuacai@kernel.org, aleksandar.qemu.devel@gmail.com, tsbogend@alpha.franken.de, anup@brainfault.org, atishp@atishpatra.org, paul.walmsley@sifive.com, palmer@dabbelt.com, aou@eecs.berkeley.edu, seanjc@google.com, pbonzini@redhat.com, dmatlack@google.com, ricarkol@google.com Cc: linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev, linux-mips@vger.kernel.org, kvm-riscv@lists.infradead.org, linux-riscv@lists.infradead.org, linux-kselftest@vger.kernel.org, kvm@vger.kernel.org, linux-kernel@vger.kernel.org, Vipin Sharma Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org Split huge pages under MMU read lock instead of write when clearing dirty log. Running huge page split under read lock will unblock vCPUs execution and allow whole clear-dirty-log operation run parallelly to vCPUs. Note that splitting huge pages involves two walkers. First walker calls stage2_split_walker() callback on each huge page. This callback will call another walker which creates an unlinked page table. This commit makes first walker as shared page walker which means, -EAGAIN will be retried. Before this patch, -EAGAIN would have been ignored and walker would go to next huge page. In practice this would not happen as the first walker was holding MMU write lock. Inner walker is unchanged as it is working on unlinked page table so no other thread will have access to it. To improve confidence in correctness tested via dirty_log_test. To measure performance improvement tested via dirty_log_perf_test. Set up: ------- Host: ARM Ampere Altra host (64 CPUs, 256 GB memory and single NUMA node) Test VM: 48 vCPU, 192 GB total memory. Ran dirty_log_perf_test for 400 iterations. ./dirty_log_perf_test -k 192G -v 48 -b 4G -m 2 -i 4000 -s anonymous_hugetlb_2mb -j Observation: ------------ +==================+=============================+===================+ | Clear Chunk size | Clear dirty log time change | vCPUs improvement | +==================+=============================+===================+ | 192GB | 56% | 152% | +------------------+-----------------------------+-------------------+ | 1GB | -81% | 72% | +------------------+-----------------------------+-------------------+ When larger chunks are used, clear dirty log time increases due to lots of cmpxchg() but vCPUs are also able to execute parallelly causing better performance of guest. When chunk size is small, read lock is very fast in clearing dirty logs as it is not waiting for MMU write lock and vCPUs are also able to run parallelly. Signed-off-by: Vipin Sharma --- arch/arm64/kvm/mmu.c | 21 ++++++++++++++------- 1 file changed, 14 insertions(+), 7 deletions(-) diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c index 6dd964e3682c..aa278f5d27a2 100644 --- a/arch/arm64/kvm/mmu.c +++ b/arch/arm64/kvm/mmu.c @@ -126,7 +126,10 @@ static int kvm_mmu_split_huge_pages(struct kvm *kvm, phys_addr_t addr, int ret, cache_capacity; u64 next, chunk_size; - lockdep_assert_held_write(&kvm->mmu_lock); + if (flags & KVM_PGTABLE_WALK_SHARED) + lockdep_assert_held_read(&kvm->mmu_lock); + else + lockdep_assert_held_write(&kvm->mmu_lock); chunk_size = kvm->arch.mmu.split_page_chunk_size; cache_capacity = kvm_mmu_split_nr_page_tables(chunk_size); @@ -138,13 +141,19 @@ static int kvm_mmu_split_huge_pages(struct kvm *kvm, phys_addr_t addr, do { if (need_split_memcache_topup_or_resched(kvm)) { - write_unlock(&kvm->mmu_lock); + if (flags & KVM_PGTABLE_WALK_SHARED) + read_unlock(&kvm->mmu_lock); + else + write_unlock(&kvm->mmu_lock); cond_resched(); /* Eager page splitting is best-effort. */ ret = __kvm_mmu_topup_memory_cache(cache, cache_capacity, cache_capacity); - write_lock(&kvm->mmu_lock); + if (flags & KVM_PGTABLE_WALK_SHARED) + read_lock(&kvm->mmu_lock); + else + write_lock(&kvm->mmu_lock); if (ret) break; } @@ -1139,9 +1148,7 @@ void kvm_arch_mmu_enable_log_dirty_pt_masked(struct kvm *kvm, read_lock(&kvm->mmu_lock); stage2_wp_range(&kvm->arch.mmu, start, end, KVM_PGTABLE_WALK_SHARED); - read_unlock(&kvm->mmu_lock); - write_lock(&kvm->mmu_lock); /* * Eager-splitting is done when manual-protect is set. We * also check for initially-all-set because we can avoid @@ -1151,8 +1158,8 @@ void kvm_arch_mmu_enable_log_dirty_pt_masked(struct kvm *kvm, * again. */ if (kvm_dirty_log_manual_protect_and_init_set(kvm)) - kvm_mmu_split_huge_pages(kvm, start, end, 0); - write_unlock(&kvm->mmu_lock); + kvm_mmu_split_huge_pages(kvm, start, end, KVM_PGTABLE_WALK_SHARED); + read_unlock(&kvm->mmu_lock); } static void kvm_send_hwpoison_signal(unsigned long address, short lsb)