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Message-ID: <Yl1wO/cqNJYf0H7Y@kernel.org>
Date: Mon, 18 Apr 2022 17:05:47 +0300
From: Mike Rapoport <rppt@...nel.org>
To: Donghyeok Kim <dthex5d@...il.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
Mike Kravetz <mike.kravetz@...cle.com>,
Christoph Lameter <cl@...ux.com>,
Pekka Enberg <penberg@...nel.org>,
David Rientjes <rientjes@...gle.com>,
Joonsoo Kim <iamjoonsoo.kim@....com>,
Vlastimil Babka <vbabka@...e.cz>,
Roman Gushchin <roman.gushchin@...ux.dev>,
Ohhoon Kwon <ohkwon1043@...il.com>,
JaeSang Yoo <jsyoo5b@...il.com>,
Wonhyuk Yang <vvghjk1234@...il.com>,
Jiyoup Kim <lakroforce@...il.com>, linux-mm@...ck.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] mm/mmzone: Introduce a new macro
for_each_node_zonelist()
On Sat, Apr 16, 2022 at 10:20:35PM +0900, Donghyeok Kim wrote:
> There are some codes using for_each_zone_zonelist() even when only
> iterating each node is needed. This commit introduces a new macro
> for_each_node_zonelist() which iterates through valid nodes in the
> zonelist.
>
> By using this new macro, code can be written in a much simpler form.
> Also, slab/slub can now skip trying to allocate from the node which was
> previously tried and failed.
>
> Co-developed-by: Ohhoon Kwon <ohkwon1043@...il.com>
> Signed-off-by: Ohhoon Kwon <ohkwon1043@...il.com>
> Signed-off-by: Donghyeok Kim <dthex5d@...il.com>
> ---
> V1 -> V2: Fix a compile error
>
> include/linux/mmzone.h | 36 ++++++++++++++++++++++++++++++++++++
> mm/hugetlb.c | 17 +++++++----------
> mm/mmzone.c | 17 +++++++++++++++++
> mm/slab.c | 7 ++-----
> mm/slub.c | 8 ++++----
> mm/vmscan.c | 16 ++++++----------
> 6 files changed, 72 insertions(+), 29 deletions(-)
Even counting the comments this does not look like a great simplification.
>
...
> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> index daa4bdd6c26c..283f28f1aca8 100644
> --- a/mm/hugetlb.c
> +++ b/mm/hugetlb.c
> @@ -1157,7 +1157,6 @@ static struct page *dequeue_huge_page_nodemask(struct hstate *h, gfp_t gfp_mask,
> {
> unsigned int cpuset_mems_cookie;
> struct zonelist *zonelist;
> - struct zone *zone;
> struct zoneref *z;
> int node = NUMA_NO_NODE;
>
> @@ -1165,18 +1164,16 @@ static struct page *dequeue_huge_page_nodemask(struct hstate *h, gfp_t gfp_mask,
>
> retry_cpuset:
> cpuset_mems_cookie = read_mems_allowed_begin();
> - for_each_zone_zonelist_nodemask(zone, z, zonelist, gfp_zone(gfp_mask), nmask) {
> +
> + /*
> + * no need to ask again on the same node. Pool is node rather than
> + * zone aware
> + */
> + for_each_node_zonelist_nodemask(node, z, zonelist, gfp_zone(gfp_mask), nmask) {
> struct page *page;
>
> - if (!cpuset_zone_allowed(zone, gfp_mask))
> - continue;
> - /*
> - * no need to ask again on the same node. Pool is node rather than
> - * zone aware
> - */
> - if (zone_to_nid(zone) == node)
> + if (!cpuset_node_allowed(node, gfp_mask))
> continue;
> - node = zone_to_nid(zone);
The actual change here seems to be the deletion of the node assignment. I'd
say it's not worth the churn.
>
> page = dequeue_huge_page_node_exact(h, node);
> if (page)
...
> diff --git a/mm/slab.c b/mm/slab.c
> index a301f266efd1..b374fb88f80e 100644
> --- a/mm/slab.c
> +++ b/mm/slab.c
> @@ -3077,7 +3077,6 @@ static void *fallback_alloc(struct kmem_cache *cache, gfp_t flags)
> {
> struct zonelist *zonelist;
> struct zoneref *z;
> - struct zone *zone;
> enum zone_type highest_zoneidx = gfp_zone(flags);
> void *obj = NULL;
> struct slab *slab;
> @@ -3096,10 +3095,8 @@ static void *fallback_alloc(struct kmem_cache *cache, gfp_t flags)
> * Look through allowed nodes for objects available
> * from existing per node queues.
> */
> - for_each_zone_zonelist(zone, z, zonelist, highest_zoneidx) {
> - nid = zone_to_nid(zone);
> -
> - if (cpuset_zone_allowed(zone, flags) &&
> + for_each_node_zonelist(nid, z, zonelist, highest_zoneidx) {
> + if (cpuset_node_allowed(nid, flags) &&
Same here.
> get_node(cache, nid) &&
> get_node(cache, nid)->free_objects) {
> obj = ____cache_alloc_node(cache,
> diff --git a/mm/slub.c b/mm/slub.c
> index 6dc703488d30..3e8b4aa98b84 100644
> --- a/mm/slub.c
> +++ b/mm/slub.c
> @@ -2192,7 +2192,7 @@ static void *get_any_partial(struct kmem_cache *s, gfp_t flags,
> #ifdef CONFIG_NUMA
> struct zonelist *zonelist;
> struct zoneref *z;
> - struct zone *zone;
> + int nid;
> enum zone_type highest_zoneidx = gfp_zone(flags);
> void *object;
> unsigned int cpuset_mems_cookie;
> @@ -2222,12 +2222,12 @@ static void *get_any_partial(struct kmem_cache *s, gfp_t flags,
> do {
> cpuset_mems_cookie = read_mems_allowed_begin();
> zonelist = node_zonelist(mempolicy_slab_node(), flags);
> - for_each_zone_zonelist(zone, z, zonelist, highest_zoneidx) {
> + for_each_node_zonelist(nid, z, zonelist, highest_zoneidx) {
> struct kmem_cache_node *n;
>
> - n = get_node(s, zone_to_nid(zone));
> + n = get_node(s, nid);
>
> - if (n && cpuset_zone_allowed(zone, flags) &&
> + if (n && cpuset_node_allowed(nid, flags) &&
> n->nr_partial > s->min_partial) {
And the changes here look rather like using different iterator variable.
> object = get_partial_node(s, n, ret_slab, flags);
> if (object) {
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index d4a7d2bd276d..342874d54c45 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -6176,9 +6176,9 @@ static unsigned long do_try_to_free_pages(struct zonelist *zonelist,
> struct scan_control *sc)
> {
> int initial_priority = sc->priority;
> - pg_data_t *last_pgdat;
> + pg_data_t *pgdat;
> struct zoneref *z;
> - struct zone *zone;
> + int nid;
> retry:
> delayacct_freepages_start();
>
> @@ -6205,20 +6205,16 @@ static unsigned long do_try_to_free_pages(struct zonelist *zonelist,
> sc->may_writepage = 1;
> } while (--sc->priority >= 0);
>
> - last_pgdat = NULL;
> - for_each_zone_zonelist_nodemask(zone, z, zonelist, sc->reclaim_idx,
> + for_each_node_zonelist_nodemask(nid, z, zonelist, sc->reclaim_idx,
> sc->nodemask) {
> - if (zone->zone_pgdat == last_pgdat)
> - continue;
> - last_pgdat = zone->zone_pgdat;
> + pgdat = NODE_DATA(nid);
I don't think this simplification is compelling enough to justify all the
changes.
>
> - snapshot_refaults(sc->target_mem_cgroup, zone->zone_pgdat);
> + snapshot_refaults(sc->target_mem_cgroup, pgdat);
>
> if (cgroup_reclaim(sc)) {
> struct lruvec *lruvec;
>
> - lruvec = mem_cgroup_lruvec(sc->target_mem_cgroup,
> - zone->zone_pgdat);
> + lruvec = mem_cgroup_lruvec(sc->target_mem_cgroup, pgdat);
> clear_bit(LRUVEC_CONGESTED, &lruvec->flags);
> }
> }
> --
> 2.17.1
>
>
--
Sincerely yours,
Mike.
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