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Re: [Qemu-block] [PATCH] migration/block: optimize the performance by co
From: |
858585 jemmy |
Subject: |
Re: [Qemu-block] [PATCH] migration/block: optimize the performance by coalescing the same write type |
Date: |
Mon, 8 May 2017 14:18:18 +0800 |
Hi Stefan&Fam:
Could you help me review this patch?
Thanks a lot.
On Mon, Apr 24, 2017 at 10:03 PM, 858585 jemmy <address@hidden> wrote:
> the reason of MIN_CLUSTER_SIZE is 8192 is base on the performance
> test result. the performance is only reduce obviously when cluster_size is
> less than 8192.
>
> I write this code, run in guest os. to create the worst condition.
>
> #include <stdio.h>
> #include <stdlib.h>
> #include <string.h>
>
> int main()
> {
> char *zero;
> char *nonzero;
> FILE* fp = fopen("./test.dat", "ab");
>
> zero = malloc(sizeof(char)*512*8);
> nonzero = malloc(sizeof(char)*512*8);
>
> memset(zero, 0, sizeof(char)*512*8);
> memset(nonzero, 1, sizeof(char)*512*8);
>
> while (1) {
> fwrite(zero, sizeof(char)*512*8, 1, fp);
> fwrite(nonzero, sizeof(char)*512*8, 1, fp);
> }
> fclose(fp);
> }
>
>
> On Mon, Apr 24, 2017 at 9:55 PM, <address@hidden> wrote:
>> From: Lidong Chen <address@hidden>
>>
>> This patch optimizes the performance by coalescing the same write type.
>> When the zero/non-zero state changes, perform the write for the accumulated
>> cluster count.
>>
>> Signed-off-by: Lidong Chen <address@hidden>
>> ---
>> Thanks Fam Zheng and Stefan's advice.
>> ---
>> migration/block.c | 66
>> +++++++++++++++++++++++++++++++++++++++++--------------
>> 1 file changed, 49 insertions(+), 17 deletions(-)
>>
>> diff --git a/migration/block.c b/migration/block.c
>> index 060087f..e9c5e21 100644
>> --- a/migration/block.c
>> +++ b/migration/block.c
>> @@ -40,6 +40,8 @@
>>
>> #define MAX_INFLIGHT_IO 512
>>
>> +#define MIN_CLUSTER_SIZE 8192
>> +
>> //#define DEBUG_BLK_MIGRATION
>>
>> #ifdef DEBUG_BLK_MIGRATION
>> @@ -923,10 +925,11 @@ static int block_load(QEMUFile *f, void *opaque, int
>> version_id)
>> }
>>
>> ret = bdrv_get_info(blk_bs(blk), &bdi);
>> - if (ret == 0 && bdi.cluster_size > 0 &&
>> - bdi.cluster_size <= BLOCK_SIZE &&
>> - BLOCK_SIZE % bdi.cluster_size == 0) {
>> + if (ret == 0 && bdi.cluster_size > 0) {
>> cluster_size = bdi.cluster_size;
>> + while (cluster_size < MIN_CLUSTER_SIZE) {
>> + cluster_size *= 2;
>> + }
>> } else {
>> cluster_size = BLOCK_SIZE;
>> }
>> @@ -943,29 +946,58 @@ static int block_load(QEMUFile *f, void *opaque, int
>> version_id)
>> nr_sectors * BDRV_SECTOR_SIZE,
>> BDRV_REQ_MAY_UNMAP);
>> } else {
>> - int i;
>> - int64_t cur_addr;
>> - uint8_t *cur_buf;
>> + int64_t cur_addr = addr * BDRV_SECTOR_SIZE;
>> + uint8_t *cur_buf = NULL;
>> + int64_t last_addr = addr * BDRV_SECTOR_SIZE;
>> + uint8_t *last_buf = NULL;
>> + int64_t end_addr = addr * BDRV_SECTOR_SIZE + BLOCK_SIZE;
>>
>> buf = g_malloc(BLOCK_SIZE);
>> qemu_get_buffer(f, buf, BLOCK_SIZE);
>> - for (i = 0; i < BLOCK_SIZE / cluster_size; i++) {
>> - cur_addr = addr * BDRV_SECTOR_SIZE + i * cluster_size;
>> - cur_buf = buf + i * cluster_size;
>> -
>> - if ((!block_mig_state.zero_blocks ||
>> - cluster_size < BLOCK_SIZE) &&
>> - buffer_is_zero(cur_buf, cluster_size)) {
>> - ret = blk_pwrite_zeroes(blk, cur_addr,
>> - cluster_size,
>> + cur_buf = buf;
>> + last_buf = buf;
>> +
>> + while (last_addr < end_addr) {
>> + int is_zero = 0;
>> + int buf_size = MIN(end_addr - cur_addr, cluster_size);
>> +
>> + /* If the "zero blocks" migration capability is enabled
>> + * and the buf_size == BLOCK_SIZE, then the source QEMU
>> + * process has already scanned for zeroes. CPU is wasted
>> + * scanning for zeroes in the destination QEMU process.
>> + */
>> + if (block_mig_state.zero_blocks &&
>> + buf_size == BLOCK_SIZE) {
>> + is_zero = 0;
>> + } else {
>> + is_zero = buffer_is_zero(cur_buf, buf_size);
>> + }
>> +
>> + cur_addr += buf_size;
>> + cur_buf += buf_size;
>> + while (cur_addr < end_addr) {
>> + buf_size = MIN(end_addr - cur_addr, cluster_size);
>> + if (is_zero != buffer_is_zero(cur_buf, buf_size)) {
>> + break;
>> + }
>> + cur_addr += buf_size;
>> + cur_buf += buf_size;
>> + }
>> +
>> + if (is_zero) {
>> + ret = blk_pwrite_zeroes(blk, last_addr,
>> + cur_addr - last_addr,
>> BDRV_REQ_MAY_UNMAP);
>> } else {
>> - ret = blk_pwrite(blk, cur_addr, cur_buf,
>> - cluster_size, 0);
>> + ret = blk_pwrite(blk, last_addr, last_buf,
>> + cur_addr - last_addr, 0);
>> }
>> if (ret < 0) {
>> break;
>> }
>> +
>> + last_addr = cur_addr;
>> + last_buf = cur_buf;
>> }
>> g_free(buf);
>> }
>> --
>> 1.8.3.1
>>
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