Migration pull patches (3rd try)

[PULL 15/30] migration/postcopy: reduce memset when it is zero page and matches_target_page_size

Juan Quintela posted 30 patches 6 years ago

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Maintainers: David Gibson <david@gibson.dropbear.id.au>, Marcel Apfelbaum <marcel.apfelbaum@gmail.com>, Laurent Vivier <lvivier@redhat.com>, Juan Quintela <quintela@redhat.com>, Peter Maydell <peter.maydell@linaro.org>, Eduardo Habkost <ehabkost@redhat.com>, Richard Henderson <rth@twiddle.net>, Paolo Bonzini <pbonzini@redhat.com>, Stefan Weil <sw@weilnetz.de>, "Michael S. Tsirkin" <mst@redhat.com>, Thomas Huth <thuth@redhat.com>, "Dr. David Alan Gilbert" <dgilbert@redhat.com>, "Marc-André Lureau" <marcandre.lureau@redhat.com>, Stefan Berger <stefanb@linux.ibm.com>, Corey Minyard <cminyard@mvista.com>, Andrzej Zaborowski <balrogg@gmail.com>, "Daniel P. Berrangé" <berrange@redhat.com>, Jason Wang <jasowang@redhat.com>

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[PULL 15/30] migration/postcopy: reduce memset when it is zero page and matches_target_page_size

Posted by Juan Quintela 6 years ago

From: Wei Yang <richardw.yang@linux.intel.com>

In this case, page_buffer content would not be used.

Skip this to save some time.

Signed-off-by: Wei Yang <richardw.yang@linux.intel.com>
Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Reviewed-by: Juan Quintela <quintela@redhat.com>
Signed-off-by: Juan Quintela <quintela@redhat.com>
---
 migration/ram.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/migration/ram.c b/migration/ram.c
index 5cd066467c..bdb0316892 100644
--- a/migration/ram.c
+++ b/migration/ram.c
@@ -4126,7 +4126,13 @@ static int ram_load_postcopy(QEMUFile *f)
         switch (flags & ~RAM_SAVE_FLAG_CONTINUE) {
         case RAM_SAVE_FLAG_ZERO:
             ch = qemu_get_byte(f);
-            memset(page_buffer, ch, TARGET_PAGE_SIZE);
+            /*
+             * Can skip to set page_buffer when
+             * this is a zero page and (block->page_size == TARGET_PAGE_SIZE).
+             */
+            if (ch || !matches_target_page_size) {
+                memset(page_buffer, ch, TARGET_PAGE_SIZE);
+            }
             if (ch) {
                 all_zero = false;
             }
-- 
2.24.1