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David Alan Gilbert" , peterx@redhat.com, Fabiano Rosas Subject: [PATCH v2 03/13] migration/postcopy: Drop all atomic ops in blocktime feature Date: Mon, 9 Jun 2025 15:12:49 -0400 Message-ID: <20250609191259.9053-4-peterx@redhat.com> X-Mailer: git-send-email 2.49.0 In-Reply-To: <20250609191259.9053-1-peterx@redhat.com> References: <20250609191259.9053-1-peterx@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Received-SPF: pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) client-ip=209.51.188.17; envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org; helo=lists.gnu.org; Received-SPF: pass client-ip=170.10.133.124; envelope-from=peterx@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H5=0.001, RCVD_IN_MSPIKE_WL=0.001, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, RCVD_IN_VALIDITY_SAFE_BLOCKED=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: qemu-devel-bounces+importer=patchew.org@nongnu.org X-ZohoMail-DKIM: pass (identity @redhat.com) X-ZM-MESSAGEID: 1749496418704116600 Content-Type: text/plain; charset="utf-8" Now with the mutex protection it's not needed anymore. Reviewed-by: Fabiano Rosas Signed-off-by: Peter Xu --- migration/postcopy-ram.c | 23 ++++++++++------------- 1 file changed, 10 insertions(+), 13 deletions(-) diff --git a/migration/postcopy-ram.c b/migration/postcopy-ram.c index 32fa06dabd..81925532de 100644 --- a/migration/postcopy-ram.c +++ b/migration/postcopy-ram.c @@ -849,12 +849,12 @@ void mark_postcopy_blocktime_begin(uintptr_t addr, ui= nt32_t ptid, =20 low_time_offset =3D get_low_time_offset(dc); if (dc->vcpu_addr[cpu] =3D=3D 0) { - qatomic_inc(&dc->smp_cpus_down); + dc->smp_cpus_down++; } =20 - qatomic_xchg(&dc->last_begin, low_time_offset); - qatomic_xchg(&dc->page_fault_vcpu_time[cpu], low_time_offset); - qatomic_xchg(&dc->vcpu_addr[cpu], addr); + dc->last_begin =3D low_time_offset; + dc->page_fault_vcpu_time[cpu] =3D low_time_offset; + dc->vcpu_addr[cpu] =3D addr; =20 /* * The caller should only inject a blocktime entry when the page is @@ -915,29 +915,26 @@ static void mark_postcopy_blocktime_end(uintptr_t add= r) for (i =3D 0; i < smp_cpus; i++) { uint32_t vcpu_blocktime =3D 0; =20 - read_vcpu_time =3D qatomic_fetch_add(&dc->page_fault_vcpu_time[i],= 0); - if (qatomic_fetch_add(&dc->vcpu_addr[i], 0) !=3D addr || - read_vcpu_time =3D=3D 0) { + read_vcpu_time =3D dc->page_fault_vcpu_time[i]; + if (dc->vcpu_addr[i] !=3D addr || read_vcpu_time =3D=3D 0) { continue; } - qatomic_xchg(&dc->vcpu_addr[i], 0); + dc->vcpu_addr[i] =3D 0; vcpu_blocktime =3D low_time_offset - read_vcpu_time; affected_cpu +=3D 1; /* we need to know is that mark_postcopy_end was due to * faulted page, another possible case it's prefetched * page and in that case we shouldn't be here */ - if (!vcpu_total_blocktime && - qatomic_fetch_add(&dc->smp_cpus_down, 0) =3D=3D smp_cpus) { + if (!vcpu_total_blocktime && dc->smp_cpus_down =3D=3D smp_cpus) { vcpu_total_blocktime =3D true; } /* continue cycle, due to one page could affect several vCPUs */ dc->vcpu_blocktime[i] +=3D vcpu_blocktime; } =20 - qatomic_sub(&dc->smp_cpus_down, affected_cpu); + dc->smp_cpus_down -=3D affected_cpu; if (vcpu_total_blocktime) { - dc->total_blocktime +=3D low_time_offset - qatomic_fetch_add( - &dc->last_begin, 0); + dc->total_blocktime +=3D low_time_offset - dc->last_begin; } trace_mark_postcopy_blocktime_end(addr, dc, dc->total_blocktime, affected_cpu); --=20 2.49.0