> 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 "/sys/module/dm_bufio/parameters/dm_bufio_cache_size". Buffers are freed when they are unused for 60 seconds (can be changed in "/sys/module/dm_bufio/parameters/dm_bufio_max_age"). 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. Mikulas > - Joe > -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
