Greg Kurz wrote on Thu, Jul 12, 2018:
> This is true when all tags have been used at least once. But the current code
> lazily allocates the wait_queue_head_t, ie, only when a tag is used for the
> first time. Your patch causes a full row of wait_quest_head_t to be
> ie, P9_ROW_MAXTAG * 24 = 255 * 24 = 6120
> instead of (P9_ROW_MAXTAG * 8) + 24 = 255 * 8 + 24 = 2064
> This is nearly a page of allocated memory that might be never used.
> Not sure if this is a problem though...
I thought the exact same, but the next patch in the serie removes that
array and allocates even more lazily with a slab, so this was a