[Spice-devel] Questions about image cache (in server/red_worker.c)

[Yaniv Kaul]

On 05/19/2011 09:18 AM, Yonit Halperin wrote:
> Hi,
> you are not looking at the right cache. THe right cache is 
> red_client_shared_cache.h  (shared among multiple monitors; doesn't 
> store images, only ids).
> The cached you looked at is the cache of the canvas.
>
> Cheers,
> Yonit.

That still doesn't make any sense to me:
- I'm looking at some kind of cache (the relevant function names are 
image_cache_put and image_cache_get). If it's not an image cache then 
someone made a poor choice of names for them.
- Per the current code, the cache has a 1024 slots hash table, yet only 
2 items max. can fit into it. If it is caching for the canvas, does it 
really need to cache only two items, and if that's so, is that the right 
way to do it?! (btw, enlarging the 2 items limit higher makes more items 
go there right away, so perhaps there is some sense in having more 
there? Donno).
- When using XP, I do see entries get into it, when using F15 I don't. 
Not sure if canvas is something you'd see in X as well.

I'll take a look at red_client_shared_cache.h . Already spotted a typo 
there.
Y.

>
> On 05/18/2011 10:54 AM, Yaniv Kaul wrote:
>> I suspect the image caching in the server is not the greatest:
>> 1. Using latest Fedora 15 and QXL driver, I don't see any image being
>> cached - at all.
>> 2. Using XP with latest QXL driver, I do see some caching activity, but
>> I suspect:
>> - the cache is limited to 2(!) items only (as IMAGE_CACHE_MAX_ITEMS 
>> is 2)
>> - even if we fix the above (so IMAGE_CACHE_MAX_ITEMS is
>> 2*IMAGE_CACHE_HASH_SIZE for example) there will be, many times, slot
>> collisions. May or may not be such a big deal, depends how much we
>> really think we'll be caching.
>> - we are not caching that many images anyway. I expected with the above
>> change to have a lot more images cached. I suspect the driver does not
>> send many images for caching to the server for some reason.
>>
>>
>> All that I've done to gather the above is sprinkle some red_printf()'s
>> after reading the code:
>>
>