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Re: [dm-devel] [PATCHES] convert dm-thin to use dm-bufio

> For me the main attraction to switching to bufio is you don't use
> dm-io.c.
> Hopefully Alasdair will allow you to keep the different memory types;
> I was allocating the buffers in bm either via kmalloc, or pages
> depending on size, but he wanted this changing to a kmem_cache in
> order to 'segregate' the memory.
> I'm not clear how you ascertain the correct working set size for your
> cache, or choose when and how many blocks to flush.  Have you got any
> documentation for this?  thinp shouldn't need a big cache and I'm a
> bit worried a 'grab another buffer if there's memory available' policy
> will make it grow too much.

The working set is 2% of memory or 1/4 of vmalloc space (whichever is 
smaller). This can be changed in 

Buffers are freed when they are unused for 60 seconds (can be changed in 

Total size is divided by the number of active clients using dm-bufio. So 
that each client gets a fair share.

Writeback is done on commit. When 3/4 of the cache size is used, 
background writeback is started.


> - Joe

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