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From: Juan Quintela <quintela@redhat.com>
To: qemu-devel@nongnu.org
Cc: "Dr. David Alan Gilbert" <dgilbert@redhat.com>,
	"Juan Quintela" <quintela@redhat.com>,
	"Eduardo Habkost" <eduardo@habkost.net>,
	"Eric Blake" <eblake@redhat.com>,
	"Marcel Apfelbaum" <marcel.apfelbaum@gmail.com>,
	"Yanan Wang" <wangyanan55@huawei.com>,
	"Markus Armbruster" <armbru@redhat.com>,
	"Philippe Mathieu-Daudé" <philmd@linaro.org>
Subject: [PATCH 07/11] multifd: Prepare to send a packet without the mutex held
Date: Mon, 28 Nov 2022 11:04:18 +0100	[thread overview]
Message-ID: <20221128100422.13522-8-quintela@redhat.com> (raw)
In-Reply-To: <20221128100422.13522-1-quintela@redhat.com>

We do the send_prepare() and the fill of the head packet without the
mutex held.  It will help a lot for compression and later in the
series for zero pages.

Notice that we can use p->pages without holding p->mutex because
p->pending_job == 1.

Signed-off-by: Juan Quintela <quintela@redhat.com>
---
 migration/multifd.h |  2 ++
 migration/multifd.c | 12 ++++++------
 2 files changed, 8 insertions(+), 6 deletions(-)

diff --git a/migration/multifd.h b/migration/multifd.h
index a67cefc0a2..cd389d18d2 100644
--- a/migration/multifd.h
+++ b/migration/multifd.h
@@ -109,7 +109,9 @@ typedef struct {
     /* array of pages to sent.
      * The owner of 'pages' depends of 'pending_job' value:
      * pending_job == 0 -> migration_thread can use it.
+     *                     No need for mutex lock.
      * pending_job != 0 -> multifd_channel can use it.
+     *                     No need for mutex lock.
      */
     MultiFDPages_t *pages;
 
diff --git a/migration/multifd.c b/migration/multifd.c
index 77196a55b4..7ebaca6e55 100644
--- a/migration/multifd.c
+++ b/migration/multifd.c
@@ -672,6 +672,8 @@ static void *multifd_send_thread(void *opaque)
                 p->flags |= MULTIFD_FLAG_SYNC;
                 p->sync_needed = false;
             }
+            qemu_mutex_unlock(&p->mutex);
+
             p->normal_num = 0;
 
             if (use_zero_copy_send) {
@@ -688,16 +690,10 @@ static void *multifd_send_thread(void *opaque)
             if (p->normal_num) {
                 ret = multifd_send_state->ops->send_prepare(p, &local_err);
                 if (ret != 0) {
-                    qemu_mutex_unlock(&p->mutex);
                     break;
                 }
             }
             multifd_send_fill_packet(p);
-            p->num_packets++;
-            p->total_normal_pages += p->normal_num;
-            p->pages->num = 0;
-            p->pages->block = NULL;
-            qemu_mutex_unlock(&p->mutex);
 
             trace_multifd_send(p->id, packet_num, p->normal_num, p->flags,
                                p->next_packet_size);
@@ -722,6 +718,10 @@ static void *multifd_send_thread(void *opaque)
             }
 
             qemu_mutex_lock(&p->mutex);
+            p->num_packets++;
+            p->total_normal_pages += p->normal_num;
+            p->pages->num = 0;
+            p->pages->block = NULL;
             p->sent_bytes += p->packet_len;
             p->sent_bytes += p->next_packet_size;
             p->pending_job--;
-- 
2.38.1



  parent reply	other threads:[~2022-11-28 10:05 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-11-28 10:04 [PATCH 00/11] Multifd zero page support Juan Quintela
2022-11-28 10:04 ` [PATCH 01/11] migration: Update atomic stats out of the mutex Juan Quintela
2022-11-28 10:04 ` [PATCH 02/11] migration: Make multifd_bytes atomic Juan Quintela
2022-11-28 10:04 ` [PATCH 03/11] multifd: We already account for this packet on the multifd thread Juan Quintela
2022-11-28 10:04 ` [PATCH 04/11] multifd: Count the number of bytes sent correctly Juan Quintela
2022-11-28 10:04 ` [PATCH 05/11] migration: Make ram_save_target_page() a pointer Juan Quintela
2022-11-28 10:04 ` [PATCH 06/11] multifd: Make flags field thread local Juan Quintela
2022-11-28 10:04 ` Juan Quintela [this message]
2022-11-28 10:04 ` [PATCH 08/11] multifd: Add capability to enable/disable zero_page Juan Quintela
2022-11-28 10:04 ` [PATCH 09/11] multifd: Support for zero pages transmission Juan Quintela
2022-11-28 10:04 ` [PATCH 10/11] multifd: Zero " Juan Quintela
2022-11-28 10:04 ` [PATCH 11/11] So we use multifd to transmit zero pages Juan Quintela

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