[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <9060a32d-b2d7-48c0-8626-1db535653c54@gmail.com>
Date: Wed, 21 Aug 2024 15:53:21 -0400
From: Usama Arif <usamaarif642@...il.com>
To: akpm@...ux-foundation.org
Cc: hannes@...xchg.org, riel@...riel.com, zhaoyang.huang@...soc.com,
yuzhao@...gle.com, david@...hat.com, leitao@...ian.org,
huangzhaoyang@...il.com, bharata@....com, willy@...radead.org,
vbabka@...e.cz, linux-kernel@...r.kernel.org, kernel-team@...a.com
Subject: Re: [PATCH] Revert "mm: skip CMA pages when they are not available"
On 21/08/2024 15:35, Usama Arif wrote:
> This reverts commit 5da226dbfce3a2f44978c2c7cf88166e69a6788b.
>
> lruvec->lru_lock is highly contended and is held when calling
> isolate_lru_folios. If the lru has a large number of CMA folios
> consecutively, while the allocation type requested is not
> MIGRATE_MOVABLE, isolate_lru_folios can hold the lock for a very long
> time while it skips those. For FIO workload, ~150million order=0
> folios were skipped to isolate a few ZONE_DMA folios [1].
> This can cause lockups [1] and high memory pressure for extended periods
> of time [2].
>
> [1] https://lore.kernel.org/all/CAOUHufbkhMZYz20aM_3rHZ3OcK4m2puji2FGpUpn_-DevGk3Kg@mail.gmail.com/
> [2] https://lore.kernel.org/all/ZrssOrcJIDy8hacI@gmail.com/
>
> Signed-off-by: Usama Arif <usamaarif642@...il.com>
> ---
> mm/vmscan.c | 3 +--
> 1 file changed, 1 insertion(+), 2 deletions(-)
>
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index 5dc96a843466..78ad4a141409 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -1690,8 +1690,7 @@ static unsigned long isolate_lru_folios(unsigned long nr_to_scan,
> nr_pages = folio_nr_pages(folio);
> total_scan += nr_pages;
>
> - if (folio_zonenum(folio) > sc->reclaim_idx ||
> - skip_cma(folio, sc)) {
> + if (folio_zonenum(folio) > sc->reclaim_idx) {
> nr_skipped[folio_zonenum(folio)] += nr_pages;
> move_to = &folios_skipped;
> goto move;
Actually, I didn't build test this with other config options before sending this patch.
skip_cma is only neeeded with MGLRU after this patch, we need to move the definition of
the function to be guarded under CONFIG_LRU_GEN, so that we don't get
‘skip_cma’ defined but not used error. Below patch should be good:
>From 1aae7f04a5cb203ea2c3ede7973dd9eddbbd7a8b Mon Sep 17 00:00:00 2001
From: Usama Arif <usamaarif642@...il.com>
Date: Wed, 21 Aug 2024 20:26:07 +0100
Subject: [PATCH] Revert "mm: skip CMA pages when they are not available"
This reverts commit 5da226dbfce3a2f44978c2c7cf88166e69a6788b.
lruvec->lru_lock is highly contended and is held when calling
isolate_lru_folios. If the lru has a large number of CMA folios
consecutively, while the allocation type requested is not
MIGRATE_MOVABLE, isolate_lru_folios can hold the lock for a very long
time while it skips those. For FIO workload, ~150million order=0
folios were skipped to isolate a few ZONE_DMA folios [1].
This can cause lockups [1] and high memory pressure for extended periods
of time [2].
[1] https://lore.kernel.org/all/CAOUHufbkhMZYz20aM_3rHZ3OcK4m2puji2FGpUpn_-DevGk3Kg@mail.gmail.com/
[2] https://lore.kernel.org/all/ZrssOrcJIDy8hacI@gmail.com/
Signed-off-by: Usama Arif <usamaarif642@...il.com>
---
mm/vmscan.c | 41 ++++++++++++++++++++---------------------
1 file changed, 20 insertions(+), 21 deletions(-)
diff --git a/mm/vmscan.c b/mm/vmscan.c
index 5dc96a843466..53372f726a1b 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -1625,25 +1625,6 @@ static __always_inline void update_lru_sizes(struct lruvec *lruvec,
}
-#ifdef CONFIG_CMA
-/*
- * It is waste of effort to scan and reclaim CMA pages if it is not available
- * for current allocation context. Kswapd can not be enrolled as it can not
- * distinguish this scenario by using sc->gfp_mask = GFP_KERNEL
- */
-static bool skip_cma(struct folio *folio, struct scan_control *sc)
-{
- return !current_is_kswapd() &&
- gfp_migratetype(sc->gfp_mask) != MIGRATE_MOVABLE &&
- folio_migratetype(folio) == MIGRATE_CMA;
-}
-#else
-static bool skip_cma(struct folio *folio, struct scan_control *sc)
-{
- return false;
-}
-#endif
-
/*
* Isolating page from the lruvec to fill in @dst list by nr_to_scan times.
*
@@ -1690,8 +1671,7 @@ static unsigned long isolate_lru_folios(unsigned long nr_to_scan,
nr_pages = folio_nr_pages(folio);
total_scan += nr_pages;
- if (folio_zonenum(folio) > sc->reclaim_idx ||
- skip_cma(folio, sc)) {
+ if (folio_zonenum(folio) > sc->reclaim_idx) {
nr_skipped[folio_zonenum(folio)] += nr_pages;
move_to = &folios_skipped;
goto move;
@@ -4297,6 +4277,25 @@ void lru_gen_soft_reclaim(struct mem_cgroup *memcg, int nid)
#endif /* CONFIG_MEMCG */
+#ifdef CONFIG_CMA
+/*
+ * It is waste of effort to scan and reclaim CMA pages if it is not available
+ * for current allocation context. Kswapd can not be enrolled as it can not
+ * distinguish this scenario by using sc->gfp_mask = GFP_KERNEL
+ */
+static bool skip_cma(struct folio *folio, struct scan_control *sc)
+{
+ return !current_is_kswapd() &&
+ gfp_migratetype(sc->gfp_mask) != MIGRATE_MOVABLE &&
+ folio_migratetype(folio) == MIGRATE_CMA;
+}
+#else
+static bool skip_cma(struct folio *folio, struct scan_control *sc)
+{
+ return false;
+}
+#endif
+
/******************************************************************************
* the eviction
******************************************************************************/
--
2.43.5
Powered by blists - more mailing lists