On 9/8/20 8:29 PM, David Hildenbrand wrote: > On 07.09.20 18:36, Vlastimil Babka wrote: >> As per the discussions [1] [2] this is an attempt to implement David's >> suggestion that page isolation should disable pcplists to avoid races. This is >> done without extra checks in fast paths, as I mentioned should be possible in >> the discussion, and explained in patch 5. Patches 1-4 are preparatory cleanups. >> >> Note this is untested RFC for now. Based on v5.9-rc4 plus Pavel's patch [2] >> (slated as a quick fix for mainline+stable). >> >> [1] https://lore.kernel.org/linux-mm/20200901124615.137200-1-pasha.tatashin@xxxxxxxxxx/ >> [2] https://lore.kernel.org/linux-mm/20200903140032.380431-1-pasha.tatashin@xxxxxxxxxx/ >> >> Vlastimil Babka (5): >> mm, page_alloc: clean up pageset high and batch update >> mm, page_alloc: calculate pageset high and batch once per zone >> mm, page_alloc(): remove setup_pageset() >> mm, page_alloc: cache pageset high and batch in struct zone >> mm, page_alloc: disable pcplists during page isolation >> >> include/linux/gfp.h | 1 + >> include/linux/mmzone.h | 2 + >> mm/internal.h | 4 ++ >> mm/memory_hotplug.c | 24 +++---- >> mm/page_alloc.c | 138 ++++++++++++++++++++++------------------- >> mm/page_isolation.c | 45 +++++++++++--- >> 6 files changed, 127 insertions(+), 87 deletions(-) >> > > Thanks for looking into this! Just a heads-up that -mm and -next contain > some changes to memory hotplug code, whereby new pageblocks start out in > MIGRATE_ISOLATE when onlining, until we're done with the heavy lifting. > Might require some tweaks, similar to when isolating pageblocks. Thanks for the heads-up. I've posted updated patch 5/5 for the -next as a reply to the first one. It was a bit tricky to order everything correctly in online_pages(), hopefully I avoided any deadlock. > Will dive into this in the following days. What's you're general > perception of performance aspects? Thanks! I expect no performance change while no isolation is in progress, as there are no new tests added in alloc/free paths. During page isolation there's a single drain instead of once-per-pageblock, which is a benefit. But the pcplists are effectively disabled for the whole of online_pages(), offline_pages() or alloc_contig_range(), which will affect parallel page allocator users. It depends on how long these operations take and how heavy the parallel usage is, so I have no good answers. Might be similar to the current periodic drain.
