On 04/18/2012 05:34 PM, Juan Quintela wrote:
> Orit Wasserman <owass...@redhat.com> wrote:
>> Add LRU page cache mechanism.
>> The page are accessed by their address.
>>
>> +
>> +typedef struct CacheItem {
>> + ram_addr_t it_addr;
>> + unsigned long it_age;
>> + uint8_t *it_data;
>> +} CacheItem;
>> +
>> +typedef struct CacheBucket {
>> + CacheItem bkt_item[CACHE_N_WAY];
>> +} CacheBucket;
>> +
>> +static CacheBucket *page_cache;
>> +static int64_t cache_num_buckets;
>> +static uint64_t cache_max_item_age;
>> +static int64_t cache_num_items;
>
> I will put this 3 variables inside CacheBucket, just to make clear that
> they are related.
OK.
>
>> +
>> +static void cache_init(int64_t num_buckets);
>> +static void cache_fini(void);
>> +static int cache_is_cached(ram_addr_t addr);
>> +static int cache_get_oldest(CacheBucket *buck);
>> +static int cache_get_newest(CacheBucket *buck, ram_addr_t addr);
>> +static void cache_insert(ram_addr_t id, uint8_t *pdata, int use_buffer);
>> +static unsigned long cache_get_cache_pos(ram_addr_t address);
>> +static CacheItem *cache_item_get(unsigned long pos, int item);
>> +static void cache_resize(int64_t new_size);
>
> None of this are needed. Notice that cache_resize is not marked static later.
>
>
>> +
>> +/***********************************************************/
>
> We normally don't use this to split code O:-)
Will be removed ...
>
>> +static void cache_init(int64_t num_bytes)
>> +{
>> + int i;
>> +
>> + cache_num_items = 0;
>> + cache_max_item_age = 0;
>> + cache_num_buckets = num_bytes / (TARGET_PAGE_SIZE * CACHE_N_WAY);
>
> Do we check that num_bytes is not negative? I can't see.
I will add a check .
>
>> + assert(cache_num_buckets);
>> + DPRINTF("Setting cache buckets to %lu\n", cache_num_buckets);
>> +
>> + assert(!page_cache);
>
> Only user of this function make page_cache = NULL before calling.
> Returning an error looks more sensible, but haven't yet looked at the
> next patechs to see if we have a way to do anything good with the error.
I guess we can fail the migration in case of an error.
>
>> + page_cache = (CacheBucket *)g_malloc((cache_num_buckets) *
>> + sizeof(CacheBucket));
>
> g_malloc() returns void * (well gpointer, but that is void*). We don't
> need to cast its return.
Will be fixed
>
>> +static int cache_is_cached(ram_addr_t addr)
>> +{
>> + unsigned long pos = cache_get_cache_pos(addr);
>> +
>> + assert(page_cache);
>> + CacheBucket *bucket = &page_cache[pos];
>> + return cache_get_newest(bucket, addr);
>> +}
>
> Can we make this function return a bool? Basically we put that anything
> != -1 means cached, -1 means non-cached.
>
sure
>> +
>> +static void cache_insert(unsigned long addr, uint8_t *pdata, int
>> use_buffer)
>
> Change use_buffer to a bool?
>
> or even better, just remove the parameter altogether and change inteface
> to:
>
> cache_insert(addr, foo, 1) -> cache_insert(addr, foo)
> cache_insert(addr, foo, 0) -> cache_insert(addr,
> g_memdup(foo,TARGET_PAGE_SIZE))
>
> and remove all the use_buffer() code?
>
>> +{
>> + unsigned long pos;
>> + int slot = -1;
>> + CacheBucket *bucket;
>> +
>> + pos = cache_get_cache_pos(addr);
>> + assert(page_cache);
>
> Function call in previous line already use page_cache, switch lines or just
> remove
> the assert?
The assert should be first .
>
>
>> +void cache_resize(int64_t new_size)
>> +{
>> + int64_t new_num_buckets = new_size/(TARGET_PAGE_SIZE * CACHE_N_WAY);
>> + CacheBucket *old_page_cache = page_cache;
>> + int i;
>> + int64_t old_num_buckets = cache_num_buckets;
>> +
>> + /* same size */
>> + if (new_num_buckets == cache_num_buckets) {
>> + return;
>> + }
>
> Shouldn't we check that new_num_buckets makes sense?
The checks are done in the calling function (patch 9) . Do you think I should
move them here ?
Orit
>
>> + /* cache was not inited */
>> + if (page_cache == NULL) {
>> + return;
>> + }
>> +
>> + /* create a new cache */
>> + page_cache = NULL;
>> + cache_init(new_size);
>
> Later, Juan.
