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SubjectRe: [PATCH v3 2/2] virtio-ring: Allocate indirect buffers from cache when possible
On 08/31/2012 12:56 PM, Michael S. Tsirkin wrote:
> On Fri, Aug 31, 2012 at 11:36:07AM +0200, Sasha Levin wrote:
>> On 08/30/2012 03:38 PM, Michael S. Tsirkin wrote:
>> >> +static unsigned int indirect_alloc_thresh = 16;
>> > Why 16? Please make is MAX_SG + 1 this makes some sense.
>>
>> Wouldn't MAX_SG mean we always allocate from the cache? Isn't the memory waste
>> too big in this case?
>
> Sorry. I really meant MAX_SKB_FRAGS + 1. MAX_SKB_FRAGS is 17 so gets us
> threshold of 18. It is less than the size of an skb+shinfo itself so -
> does it look too big to you? Also why do you think 16 is not too big but
> 18 is? If there's a reason then I am fine with 16 too but then please
> put it in code comment near where the value is set.
>
> Yes this means virtio net always allocates from cache
> but this is a good thing, isn't it? Gets us more consistent
> performance.

kmalloc() also goes to a cache. Is there a measurable difference?

Ugh, there's an ugly loop in __find_general_cachep(), which really wants
to be replaced with fls().

--
error compiling committee.c: too many arguments to function


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