Re: [Qemu-devel] [PATCH 5/6] save_block_hdr: we can recalculate the cont parameter here

[Juan Quintela]

"Li, Liang Z"  wrote:
>> -Original Message-
>> From: Juan Quintela [mailto:quint...@redhat.com]
>> Sent: Friday, February 13, 2015 6:03 AM
>> To: qemu-devel@nongnu.org
>> Cc: Li, Liang Z
>> Subject: [PATCH 5/6] save_block_hdr: we can recalculate the cont parameter
>> here
>> 
>> No need to pass it through all the callers.  Once there, update
>> last_sent_block here.
>> 
>> Signed-off-by: Juan Quintela 
>> ---
>>  arch_init.c | 47 ---
>>  1 file changed, 24 insertions(+), 23 deletions(-)
>> 
>> diff --git a/arch_init.c b/arch_init.c
>> index 834f40c..95a61e2 100644
>> --- a/arch_init.c
>> +++ b/arch_init.c
>> @@ -304,34 +304,39 @@ uint64_t xbzrle_mig_pages_overflow(void)
>>  return acct_info.xbzrle_overflows;
>>  }
>> 
>> +/* This is the last block that we have visited serching for dirty pages
>> +*/ static RAMBlock *last_seen_block;
>> +/* This is the last block from where we have sent data */ static
>> +RAMBlock *last_sent_block; static ram_addr_t last_offset; static
>> +unsigned long *migration_bitmap; static uint64_t migration_dirty_pages;
>> +static uint32_t last_version; static bool ram_bulk_stage;
>> +
>>  static size_t save_block_hdr(QEMUFile *f, RAMBlock *block, ram_addr_t
>> offset,
>> - int cont, int flag)
>> + int flag)
>>  {
>>  size_t size;
>> 
>> -qemu_put_be64(f, offset | cont | flag);
>> +if (block == last_sent_block) {
>> +offset |= RAM_SAVE_FLAG_CONTINUE;
>> +}
>> +
>> +qemu_put_be64(f, offset | flag);
>>  size = 8;
>> 
>> -if (!cont) {
>> +if (block != last_sent_block) {
>>  qemu_put_byte(f, strlen(block->idstr));
>>  qemu_put_buffer(f, (uint8_t *)block->idstr,
>>  strlen(block->idstr));
>>  size += 1 + strlen(block->idstr);
>> +last_sent_block = block;
>>  }
>>  return size;
>>  }
>
> If save_block_hdr function is changed to this, then in my patch, it
> can't not be directly reused in
> compression thread. A lock is needed to access last_sent_block. I
> prefer the original implementation.

ah

ok, will redo this then.

Thanks for the feedback.

Later, Juan.

[Qemu-devel] [PATCH 5/6] save_block_hdr: we can recalculate the cont parameter here

[Juan Quintela]

No need to pass it through all the callers.  Once there, update
last_sent_block here.

Signed-off-by: Juan Quintela 
---
 arch_init.c | 47 ---
 1 file changed, 24 insertions(+), 23 deletions(-)

diff --git a/arch_init.c b/arch_init.c
index 834f40c..95a61e2 100644
--- a/arch_init.c
+++ b/arch_init.c
@@ -304,34 +304,39 @@ uint64_t xbzrle_mig_pages_overflow(void)
 return acct_info.xbzrle_overflows;
 }

+/* This is the last block that we have visited serching for dirty pages
+ */
+static RAMBlock *last_seen_block;
+/* This is the last block from where we have sent data */
+static RAMBlock *last_sent_block;
+static ram_addr_t last_offset;
+static unsigned long *migration_bitmap;
+static uint64_t migration_dirty_pages;
+static uint32_t last_version;
+static bool ram_bulk_stage;
+
 static size_t save_block_hdr(QEMUFile *f, RAMBlock *block, ram_addr_t offset,
- int cont, int flag)
+ int flag)
 {
 size_t size;

-qemu_put_be64(f, offset | cont | flag);
+if (block == last_sent_block) {
+offset |= RAM_SAVE_FLAG_CONTINUE;
+}
+
+qemu_put_be64(f, offset | flag);
 size = 8;

-if (!cont) {
+if (block != last_sent_block) {
 qemu_put_byte(f, strlen(block->idstr));
 qemu_put_buffer(f, (uint8_t *)block->idstr,
 strlen(block->idstr));
 size += 1 + strlen(block->idstr);
+last_sent_block = block;
 }
 return size;
 }

-/* This is the last block that we have visited serching for dirty pages
- */
-static RAMBlock *last_seen_block;
-/* This is the last block from where we have sent data */
-static RAMBlock *last_sent_block;
-static ram_addr_t last_offset;
-static unsigned long *migration_bitmap;
-static uint64_t migration_dirty_pages;
-static uint32_t last_version;
-static bool ram_bulk_stage;
-
 /* Update the xbzrle cache to reflect a page that's been sent as all 0.
  * The important thing is that a stale (not-yet-0'd) page be replaced
  * by the new data.
@@ -369,7 +374,7 @@ static void xbzrle_cache_zero_page(ram_addr_t current_addr)
  */
 static int save_xbzrle_page(QEMUFile *f, uint8_t **current_data,
 ram_addr_t current_addr, RAMBlock *block,
-ram_addr_t offset, int cont, bool last_stage,
+ram_addr_t offset, bool last_stage,
 uint64_t *bytes_transferred)
 {
 int encoded_len = 0, bytes_xbzrle;
@@ -419,7 +424,7 @@ static int save_xbzrle_page(QEMUFile *f, uint8_t 
**current_data,
 }

 /* Send XBZRLE based compressed page */
-bytes_xbzrle = save_block_hdr(f, block, offset, cont, 
RAM_SAVE_FLAG_XBZRLE);
+bytes_xbzrle = save_block_hdr(f, block, offset, RAM_SAVE_FLAG_XBZRLE);
 qemu_put_byte(f, ENCODING_FLAG_XBZRLE);
 qemu_put_be16(f, encoded_len);
 qemu_put_buffer(f, XBZRLE.encoded_buf, encoded_len);
@@ -604,15 +609,12 @@ static int ram_save_page(QEMUFile *f, RAMBlock* block, 
ram_addr_t offset,
 {
 int pages = -1;
 uint64_t bytes_xmit;
-int cont;
 ram_addr_t current_addr;
 MemoryRegion *mr = block->mr;
 uint8_t *p;
 int ret;
 bool send_async = true;

-cont = (block == last_sent_block) ? RAM_SAVE_FLAG_CONTINUE : 0;
-
 p = memory_region_get_ram_ptr(mr) + offset;

 /* In doubt sent page as normal */
@@ -637,7 +639,7 @@ static int ram_save_page(QEMUFile *f, RAMBlock* block, 
ram_addr_t offset,
 }
 } else if (is_zero_range(p, TARGET_PAGE_SIZE)) {
 acct_info.dup_pages++;
-*bytes_transferred += save_block_hdr(f, block, offset, cont,
+*bytes_transferred += save_block_hdr(f, block, offset,
  RAM_SAVE_FLAG_COMPRESS);
 qemu_put_byte(f, 0);
 *bytes_transferred += 1;
@@ -648,7 +650,7 @@ static int ram_save_page(QEMUFile *f, RAMBlock* block, 
ram_addr_t offset,
 xbzrle_cache_zero_page(current_addr);
 } else if (!ram_bulk_stage && migrate_use_xbzrle()) {
 pages = save_xbzrle_page(f, &p, current_addr, block,
- offset, cont, last_stage, bytes_transferred);
+ offset, last_stage, bytes_transferred);
 if (!last_stage) {
 /* Can't send this cached data async, since the cache page
  * might get updated before it gets to the wire
@@ -659,7 +661,7 @@ static int ram_save_page(QEMUFile *f, RAMBlock* block, 
ram_addr_t offset,

 /* XBZRLE overflow or normal page */
 if (pages == -1) {
-*bytes_transferred += save_block_hdr(f, block, offset, cont,
+*bytes_transferred += save_block_hdr(f, block, offset,
  RAM_SAVE_FLAG_PAGE);
 if (send_async) {
 qemu_put_buffer_async(f, p, TARGET_PAGE_SIZE);
@@ -720,7 +722,6 @@ static int ram_find_and_save_block(QEMUFile *f, bool 
last_stage,