Re: [Qemu-trivial] [PATCH 1/1] virtio-blk: Use a req pool instead of malloc/free

["Li, ZhenHua" <zhen-hual@hp.com>]

I am sorry that seems it was not sent out before I subscribed to the 
list. So I send this patch again.

On 03/26/2014 10:02 AM, Li, Zhen-Hua wrote:
> From: "Li, ZhenHua" <zhen-hual@hp.com>
>
> In virtio-blk module, when there is new request, new req structure
> will be created by malloc.  Use a req pool instead of this, will increase
> performance;
>
> Increacement: about 5% to 10%.
>
> Signed-off-by: Li, ZhenHua <zhen-hual@hp.com>
> ---
>   hw/block/virtio-blk.c |   87 ++++++++++++++++++++++++++++++++++++++++++-------
>   1 file changed, 75 insertions(+), 12 deletions(-)
>
> diff --git a/hw/block/virtio-blk.c b/hw/block/virtio-blk.c
> index 8a568e5..da5b570 100644
> --- a/hw/block/virtio-blk.c
> +++ b/hw/block/virtio-blk.c
> @@ -39,6 +39,70 @@ typedef struct VirtIOBlockReq
>       BlockAcctCookie acct;
>   } VirtIOBlockReq;
>
> +#define POOL_PAGE 512
> +static VirtIOBlockReq * * req_pool;
> +static char * req_pool_used;
> +static unsigned long req_pool_size = 0;
> +
> +static void remalloc_reqs(void){
> +    unsigned long old_size = req_pool_size;
> +    unsigned long int i;
> +    char * old_used = req_pool_used;
> +    VirtIOBlockReq * * old_pool = req_pool;
> +
> +    req_pool_size += POOL_PAGE;
> +    req_pool_used = (char * )malloc(req_pool_size * sizeof(char));
> +    req_pool =  (VirtIOBlockReq * * )malloc(req_pool_size * sizeof(VirtIOBlockReq *));
> +
> +    if(old_size != 0){
> +        memcpy(req_pool_used, old_used, old_size*(sizeof(char)));
> +        memcpy(req_pool, old_pool, old_size*(sizeof(VirtIOBlockReq *)));
> +    }
> +    for(i=old_size; i<req_pool_size; i++){
> +    	req_pool[i] = (VirtIOBlockReq *)malloc(sizeof(VirtIOBlockReq));
> +    	req_pool_used[i] = 0;
> +    }
> +
> +    if(old_size != 0){
> +    	free(old_used);
> +    	free(old_pool);
> +    }
> +}
> +static VirtIOBlockReq * req_pool_get_new(void){
> +    unsigned long int i;
> +    char * used;
> +    VirtIOBlockReq * * req;
> +
> +    if(req_pool_size == 0){
> +        remalloc_reqs();
> +    }
> +    for(i=0, used=req_pool_used, req=req_pool;
> +            i<req_pool_size; i++, used ++, req++){
> +    	if(*used == 0){
> +            *used = 1;
> +            return *req;
> +        }
> +    }
> +    remalloc_reqs();
> +    req_pool_used[req_pool_size-POOL_PAGE] = 1;
> +    *req = req_pool[req_pool_size-POOL_PAGE];
> +    return *req;
> +}
> +
> +static void virtio_blk_free_request(VirtIOBlockReq *req0){
> +    unsigned long int i;
> +    char * used;
> +    VirtIOBlockReq * * req;
> +
> +    for(i=0, used=req_pool_used, req=req_pool;
> +            i<req_pool_size; i++, used ++, req++){
> +    	if(*req == req0){
> +            *used = 0;
> +        }
> +    }
> +}
> +
> +
>   static void virtio_blk_req_complete(VirtIOBlockReq *req, int status)
>   {
>       VirtIOBlock *s = req->dev;
> @@ -63,7 +127,7 @@ static int virtio_blk_handle_rw_error(VirtIOBlockReq *req, int error,
>       } else if (action == BDRV_ACTION_REPORT) {
>           virtio_blk_req_complete(req, VIRTIO_BLK_S_IOERR);
>           bdrv_acct_done(s->bs, &req->acct);
> -        g_free(req);
> +        virtio_blk_free_request(req);
>       }
>
>       bdrv_error_action(s->bs, action, is_read, error);
> @@ -84,7 +148,7 @@ static void virtio_blk_rw_complete(void *opaque, int ret)
>
>       virtio_blk_req_complete(req, VIRTIO_BLK_S_OK);
>       bdrv_acct_done(req->dev->bs, &req->acct);
> -    g_free(req);
> +    virtio_blk_free_request(req);
>   }
>
>   static void virtio_blk_flush_complete(void *opaque, int ret)
> @@ -99,25 +163,24 @@ static void virtio_blk_flush_complete(void *opaque, int ret)
>
>       virtio_blk_req_complete(req, VIRTIO_BLK_S_OK);
>       bdrv_acct_done(req->dev->bs, &req->acct);
> -    g_free(req);
> +    virtio_blk_free_request(req);
>   }
> -
>   static VirtIOBlockReq *virtio_blk_alloc_request(VirtIOBlock *s)
>   {
> -    VirtIOBlockReq *req = g_malloc(sizeof(*req));
> +    VirtIOBlockReq *req ;
> +    req = req_pool_get_new();
>       req->dev = s;
>       req->qiov.size = 0;
>       req->next = NULL;
>       return req;
>   }
> -
>   static VirtIOBlockReq *virtio_blk_get_request(VirtIOBlock *s)
>   {
>       VirtIOBlockReq *req = virtio_blk_alloc_request(s);
>
>       if (req != NULL) {
>           if (!virtqueue_pop(s->vq, &req->elem)) {
> -            g_free(req);
> +            virtio_blk_free_request(req);
>               return NULL;
>           }
>       }
> @@ -142,7 +205,7 @@ static void virtio_blk_handle_scsi(VirtIOBlockReq *req)
>        */
>       if (req->elem.out_num < 2 || req->elem.in_num < 3) {
>           virtio_blk_req_complete(req, VIRTIO_BLK_S_IOERR);
> -        g_free(req);
> +        virtio_blk_free_request(req);
>           return;
>       }
>
> @@ -232,7 +295,7 @@ static void virtio_blk_handle_scsi(VirtIOBlockReq *req)
>       stl_p(&req->scsi->data_len, hdr.dxfer_len);
>
>       virtio_blk_req_complete(req, status);
> -    g_free(req);
> +    virtio_blk_free_request(req);
>       return;
>   #else
>       abort();
> @@ -242,7 +305,7 @@ fail:
>       /* Just put anything nonzero so that the ioctl fails in the guest.  */
>       stl_p(&req->scsi->errors, 255);
>       virtio_blk_req_complete(req, status);
> -    g_free(req);
> +    virtio_blk_free_request(req);
>   }
>
>   typedef struct MultiReqBuffer {
> @@ -375,7 +438,7 @@ static void virtio_blk_handle_request(VirtIOBlockReq *req,
>                   s->blk.serial ? s->blk.serial : "",
>                   MIN(req->elem.in_sg[0].iov_len, VIRTIO_BLK_ID_BYTES));
>           virtio_blk_req_complete(req, VIRTIO_BLK_S_OK);
> -        g_free(req);
> +        virtio_blk_free_request(req);
>       } else if (type & VIRTIO_BLK_T_OUT) {
>           qemu_iovec_init_external(&req->qiov, &req->elem.out_sg[1],
>                                    req->elem.out_num - 1);
> @@ -387,7 +450,7 @@ static void virtio_blk_handle_request(VirtIOBlockReq *req,
>           virtio_blk_handle_read(req);
>       } else {
>           virtio_blk_req_complete(req, VIRTIO_BLK_S_UNSUPP);
> -        g_free(req);
> +        virtio_blk_free_request(req);
>       }
>   }
>
>