Thanks Michal, Hi, raghavendra, Jens Could you help comment this issue? Thanks in advance. -----Original Message----- From: Michal Hocko [mailto:mhocko@xxxxxxxx] Sent: Monday, October 19, 2020 7:40 PM To: tianxianting (RD) <tian.xianting@xxxxxxx> Cc: axboe@xxxxxxxxx; raghavendra.kt@xxxxxxxxxxxxxxxxxx; linux-block@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx Subject: Re: [PATCH] blk-mq: remove the calling of local_memory_node() On Mon 19-10-20 16:20:47, Xianting Tian wrote: > We don't need to check whether the node is memoryless numa node before > calling allocator interface. SLUB(and SLAB,SLOB) relies on the page > allocator to pick a node. Page allocator should deal with memoryless > nodes just fine. It has zonelists constructed for each possible nodes. > And it will automatically fall back into a node which is closest to > the requested node. As long as __GFP_THISNODE is not enforced of course. > > The code comments of kmem_cache_alloc_node() of SLAB also showed this: > * Fallback to other node is possible if __GFP_THISNODE is not set. > > blk-mq code doesn't set __GFP_THISNODE, so we can remove the calling > of local_memory_node(). yes, this is indeed the case. I cannot really judge the blg-mq code but it seems to be unnecessary. Maybe there are some subtle details not explained by bffed457160ab though. > Fixes: bffed457160ab ("blk-mq: Avoid memoryless numa node encoded in > hctx numa_node") But the existing code is not broken. It just overdoes what needs to be done. So effectively bffed457160ab was not needed. I do not think that Fixes is really necessary. > Signed-off-by: Xianting Tian <tian.xianting@xxxxxxx> > --- > block/blk-mq-cpumap.c | 2 +- > block/blk-mq.c | 2 +- > 2 files changed, 2 insertions(+), 2 deletions(-) > > diff --git a/block/blk-mq-cpumap.c b/block/blk-mq-cpumap.c index > 0157f2b34..3db84d319 100644 > --- a/block/blk-mq-cpumap.c > +++ b/block/blk-mq-cpumap.c > @@ -89,7 +89,7 @@ int blk_mq_hw_queue_to_node(struct blk_mq_queue_map > *qmap, unsigned int index) > > for_each_possible_cpu(i) { > if (index == qmap->mq_map[i]) > - return local_memory_node(cpu_to_node(i)); > + return cpu_to_node(i); > } > > return NUMA_NO_NODE; > diff --git a/block/blk-mq.c b/block/blk-mq.c index > cdced4aca..48f8366b2 100644 > --- a/block/blk-mq.c > +++ b/block/blk-mq.c > @@ -2737,7 +2737,7 @@ static void blk_mq_init_cpu_queues(struct request_queue *q, > for (j = 0; j < set->nr_maps; j++) { > hctx = blk_mq_map_queue_type(q, j, i); > if (nr_hw_queues > 1 && hctx->numa_node == NUMA_NO_NODE) > - hctx->numa_node = local_memory_node(cpu_to_node(i)); > + hctx->numa_node = cpu_to_node(i); > } > } > } > -- > 2.17.1 -- Michal Hocko SUSE Labs
