Re: [Qemu-devel] [PATCH v5 09/11] curl: add cache quota.

[Stefan Hajnoczi]

On Thu, May 23, 2013 at 11:38:07AM +0800, Fam Zheng wrote:
> Introduce a cache quota: BDRVCURLState.cache_quota.
> When adding new CURLDataCache to BDRVCURLState, if number of existing
> CURLDataCache is larger than CURL_CACHE_QUOTA, try to release some first
> to limit the in memory cache size.
> 
> A least used entry is selected for releasing.
> 
> Signed-off-by: Fam Zheng <address@hidden>
> ---
>  block/curl.c | 27 +++++++++++++++++++++++++++
>  1 file changed, 27 insertions(+)
> 
> diff --git a/block/curl.c b/block/curl.c
> index 3ea2552..5adbc84 100644
> --- a/block/curl.c
> +++ b/block/curl.c
> @@ -40,6 +40,7 @@
>  
>  #define SECTOR_SIZE     512
>  #define READ_AHEAD_SIZE (256 * 1024)
> +#define CURL_CACHE_QUOTA 10
>  
>  struct BDRVCURLState;
>  
> @@ -90,6 +91,8 @@ typedef struct BDRVCURLState {
>      QEMUTimer *timer;
>      /* List of data cache ordered by access, freed from tail */
>      QLIST_HEAD(, CURLDataCache) cache;
> +    /* Threshold to release unused cache when cache list is longer than it */
> +    int cache_quota;
>      /* Whether http server accept range in header */
>      bool accept_range;
>  } BDRVCURLState;
> @@ -526,6 +529,8 @@ static int curl_open(BlockDriverState *bs, QDict 
> *options, int flags)
>      curl_multi_socket_action(s->multi, CURL_SOCKET_TIMEOUT, 0, &running);
>  
>      qemu_opts_del(opts);
> +    s->cache_quota = CURL_CACHE_QUOTA;
> +
>      return 0;
>  
>  out:
> @@ -595,6 +600,27 @@ static void curl_readv_bh_cb(void *p)
>      cache->data_len = aio_bytes + s->readahead_size;
>      cache->write_pos = 0;
>      cache->data = g_malloc(cache->data_len);
> +    /* Try to release some cache */
> +    while (0 && s->cache_quota <= 0) {

while (0) :(