Phil, My apologies for missing this. This thread is getting long. Regardless, the max stripe_cache_size will not use more than 256MB of RAM (32K x 8K) for a single device, and the memory usage will be static. Doug On Fri, Aug 26, 2016 at 2:57 PM, Phil Turmel <philip@xxxxxxxxxx> wrote: > On 08/26/2016 04:04 PM, Doug Dumitru wrote: >> I took a simple array from stripe_cache_size 256 => 32K and the system >> allocated 265 MB of RAM (crude number via free), so this implies that >> the stripe cache is 8K per entry. The stripe cache struct appears to >> have a bio plus a bunch of other control items in the struct. I am >> not sure if it has a statically allocated page, but at 8K it looks >> like it does. So I think the minimum/static memory allocated by the >> stripe cache is 8K per entry. This "might" also be the maximum, or >> the cache size might grow to handle longer requests. > > This was answered three days ago. Allow me to quote myself: > >> This is not correct. Parity operations in MD raid4/5/6 operate on 4k >> blocks. The stripe cache for an array is a collection of 4k elements >> per member device. Chunk size doesn't factor into the cache itself. > > Phil > -- Doug Dumitru EasyCo LLC -- To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
