On Fri, 8 Dec 2017 12:42:17 +0100 Lucas Stach <l.stach@xxxxxxxxxxxxxx> wrote: > Since 9cca35d42eb6 (mm, page_alloc: enable/disable IRQs once when freeing > a list of pages) we see excessive IRQ disabled times of up to 25ms on an > embedded ARM system (tracing overhead included). > > This is due to graphics buffers being freed back to the system via > release_pages(). Graphics buffers can be huge, so it's not hard to hit > cases where the list of pages to free has 2048 entries. Disabling IRQs > while freeing all those pages is clearly not a good idea. > > Introduce a batch limit, which allows IRQ servicing once every few pages. > The batch count is the same as used in other parts of the MM subsystem > when dealing with IRQ disabled regions. > > Signed-off-by: Lucas Stach <l.stach@xxxxxxxxxxxxxx> > Suggested-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> > --- > v2: Try to keep the working set of pages used in the second loop cache > hot by going through both loops in swathes of SWAP_CLUSTER_MAX > entries, as suggested by Andrew Morton. > > To avoid the need to replicate the batch counting in both loops > I introduced a local batched_free_list where pages to be freed > in the critical section are collected. IMO this makes the code > easier to follow. Thanks. Is anyone motivated enough to determine whether this is worthwhile? -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>
