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Message-ID: <20250320173931.1583800-3-surenb@google.com>
Date: Thu, 20 Mar 2025 10:39:30 -0700
From: Suren Baghdasaryan <surenb@...gle.com>
To: akpm@...ux-foundation.org
Cc: willy@...radead.org, david@...hat.com, vbabka@...e.cz,
lorenzo.stoakes@...cle.com, liam.howlett@...cle.com, alexandru.elisei@....com,
peterx@...hat.com, hannes@...xchg.org, mhocko@...nel.org,
m.szyprowski@...sung.com, iamjoonsoo.kim@....com, mina86@...a86.com,
axboe@...nel.dk, viro@...iv.linux.org.uk, brauner@...nel.org,
hch@...radead.org, jack@...e.cz, hbathini@...ux.ibm.com,
sourabhjain@...ux.ibm.com, ritesh.list@...il.com, aneesh.kumar@...nel.org,
bhelgaas@...gle.com, sj@...nel.org, fvdl@...gle.com, ziy@...dia.com,
yuzhao@...gle.com, minchan@...nel.org, surenb@...gle.com, linux-mm@...ck.org,
linuxppc-dev@...ts.ozlabs.org, linux-block@...r.kernel.org,
linux-fsdevel@...r.kernel.org, iommu@...ts.linux.dev,
linux-kernel@...r.kernel.org, Minchan Kim <minchan@...gle.com>
Subject: [RFC 2/3] mm: introduce GCMA
From: Minchan Kim <minchan@...gle.com>
This patch introduces GCMA (Guaranteed Contiguous Memory Allocator)
cleacache backend which reserves some amount of memory at the boot
and then donates it to store clean file-backed pages in the cleancache.
GCMA aims to guarantee contiguous memory allocation success as well as
low and deterministic allocation latency.
Notes:
Originally, the idea was posted by SeongJae Park and Minchan Kim [1].
Later Minchan reworked it to be used in Android as a reference for
Android vendors to use [2].
[1] https://lwn.net/Articles/619865/
[2] https://android-review.googlesource.com/q/topic:%22gcma_6.12%22
Signed-off-by: Minchan Kim <minchan@...gle.com>
Signed-off-by: Suren Baghdasaryan <surenb@...gle.com>
---
include/linux/gcma.h | 12 ++++
mm/Kconfig | 15 +++++
mm/Makefile | 1 +
mm/gcma.c | 155 +++++++++++++++++++++++++++++++++++++++++++
4 files changed, 183 insertions(+)
create mode 100644 include/linux/gcma.h
create mode 100644 mm/gcma.c
diff --git a/include/linux/gcma.h b/include/linux/gcma.h
new file mode 100644
index 000000000000..2ce40fcc74a5
--- /dev/null
+++ b/include/linux/gcma.h
@@ -0,0 +1,12 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __GCMA_H__
+#define __GCMA_H__
+
+#include <linux/types.h>
+
+int gcma_register_area(const char *name,
+ unsigned long start_pfn, unsigned long count);
+void gcma_alloc_range(unsigned long start_pfn, unsigned long count);
+void gcma_free_range(unsigned long start_pfn, unsigned long count);
+
+#endif /* __GCMA_H__ */
diff --git a/mm/Kconfig b/mm/Kconfig
index d6ebf0fb0432..85268ef901b6 100644
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -1002,6 +1002,21 @@ config CMA_AREAS
If unsure, leave the default value "8" in UMA and "20" in NUMA.
+config GCMA
+ bool "GCMA (Guaranteed Contiguous Memory Allocator)"
+ depends on CLEANCACHE
+ help
+ This enables the Guaranteed Contiguous Memory Allocator to allow
+ low latency guaranteed contiguous memory allocations. Memory
+ reserved by GCMA is donated to cleancache to be used as pagecache
+ extension. Once GCMA allocation is requested, necessary pages are
+ taken back from the cleancache and used to satisfy the request.
+ Cleancache guarantees low latency successful allocation as long
+ as the total size of GCMA allocations does not exceed the size of
+ the memory donated to the cleancache.
+
+ If unsure, say "N".
+
config MEM_SOFT_DIRTY
bool "Track memory changes"
depends on CHECKPOINT_RESTORE && HAVE_ARCH_SOFT_DIRTY && PROC_FS
diff --git a/mm/Makefile b/mm/Makefile
index 084dbe9edbc4..2173d395d371 100644
--- a/mm/Makefile
+++ b/mm/Makefile
@@ -149,3 +149,4 @@ obj-$(CONFIG_EXECMEM) += execmem.o
obj-$(CONFIG_TMPFS_QUOTA) += shmem_quota.o
obj-$(CONFIG_PT_RECLAIM) += pt_reclaim.o
obj-$(CONFIG_CLEANCACHE) += cleancache.o
+obj-$(CONFIG_GCMA) += gcma.o
diff --git a/mm/gcma.c b/mm/gcma.c
new file mode 100644
index 000000000000..263e63da0c89
--- /dev/null
+++ b/mm/gcma.c
@@ -0,0 +1,155 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * GCMA (Guaranteed Contiguous Memory Allocator)
+ *
+ */
+
+#define pr_fmt(fmt) "gcma: " fmt
+
+#include <linux/cleancache.h>
+#include <linux/gcma.h>
+#include <linux/hashtable.h>
+#include <linux/highmem.h>
+#include <linux/idr.h>
+#include <linux/slab.h>
+#include <linux/xarray.h>
+
+#define MAX_GCMA_AREAS 64
+#define GCMA_AREA_NAME_MAX_LEN 32
+
+struct gcma_area {
+ int area_id;
+ unsigned long start_pfn;
+ unsigned long end_pfn;
+ char name[GCMA_AREA_NAME_MAX_LEN];
+};
+
+static struct gcma_area areas[MAX_GCMA_AREAS];
+static atomic_t nr_gcma_area = ATOMIC_INIT(0);
+static DEFINE_SPINLOCK(gcma_area_lock);
+
+static void alloc_page_range(struct gcma_area *area,
+ unsigned long start_pfn, unsigned long end_pfn)
+{
+ unsigned long scanned = 0;
+ unsigned long pfn;
+ struct page *page;
+ int err;
+
+ for (pfn = start_pfn; pfn < end_pfn; pfn++) {
+ if (!(++scanned % XA_CHECK_SCHED))
+ cond_resched();
+
+ page = pfn_to_page(pfn);
+ err = cleancache_backend_get_folio(area->area_id, page_folio(page));
+ VM_BUG_ON(err);
+ }
+}
+
+static void free_page_range(struct gcma_area *area,
+ unsigned long start_pfn, unsigned long end_pfn)
+{
+ unsigned long scanned = 0;
+ unsigned long pfn;
+ struct page *page;
+ int err;
+
+ for (pfn = start_pfn; pfn < end_pfn; pfn++) {
+ if (!(++scanned % XA_CHECK_SCHED))
+ cond_resched();
+
+ page = pfn_to_page(pfn);
+ err = cleancache_backend_put_folio(area->area_id,
+ page_folio(page));
+ VM_BUG_ON(err);
+ }
+}
+
+int gcma_register_area(const char *name,
+ unsigned long start_pfn, unsigned long count)
+{
+ LIST_HEAD(folios);
+ int i, area_id;
+ int nr_area;
+ int ret = 0;
+
+ for (i = 0; i < count; i++) {
+ struct folio *folio;
+
+ folio = page_folio(pfn_to_page(start_pfn + i));
+ list_add(&folio->lru, &folios);
+ }
+
+ area_id = cleancache_register_backend(name, &folios);
+ if (area_id < 0)
+ return area_id;
+
+ spin_lock(&gcma_area_lock);
+
+ nr_area = atomic_read(&nr_gcma_area);
+ if (nr_area < MAX_GCMA_AREAS) {
+ struct gcma_area *area = &areas[nr_area];
+
+ area->area_id = area_id;
+ area->start_pfn = start_pfn;
+ area->end_pfn = start_pfn + count;
+ strscpy(area->name, name);
+ /* Ensure above stores complete before we increase the count */
+ atomic_set_release(&nr_gcma_area, nr_area + 1);
+ } else {
+ ret = -ENOMEM;
+ }
+
+ spin_unlock(&gcma_area_lock);
+
+ return ret;
+}
+EXPORT_SYMBOL_GPL(gcma_register_area);
+
+void gcma_alloc_range(unsigned long start_pfn, unsigned long count)
+{
+ int nr_area = atomic_read_acquire(&nr_gcma_area);
+ unsigned long end_pfn = start_pfn + count;
+ struct gcma_area *area;
+ int i;
+
+ for (i = 0; i < nr_area; i++) {
+ unsigned long s_pfn, e_pfn;
+
+ area = &areas[i];
+ if (area->end_pfn <= start_pfn)
+ continue;
+
+ if (area->start_pfn > end_pfn)
+ continue;
+
+ s_pfn = max(start_pfn, area->start_pfn);
+ e_pfn = min(end_pfn, area->end_pfn);
+ alloc_page_range(area, s_pfn, e_pfn);
+ }
+}
+EXPORT_SYMBOL_GPL(gcma_alloc_range);
+
+void gcma_free_range(unsigned long start_pfn, unsigned long count)
+{
+ int nr_area = atomic_read_acquire(&nr_gcma_area);
+ unsigned long end_pfn = start_pfn + count;
+ struct gcma_area *area;
+ int i;
+
+ for (i = 0; i < nr_area; i++) {
+ unsigned long s_pfn, e_pfn;
+
+ area = &areas[i];
+ if (area->end_pfn <= start_pfn)
+ continue;
+
+ if (area->start_pfn > end_pfn)
+ continue;
+
+ s_pfn = max(start_pfn, area->start_pfn);
+ e_pfn = min(end_pfn, area->end_pfn);
+ free_page_range(area, s_pfn, e_pfn);
+ }
+}
+EXPORT_SYMBOL_GPL(gcma_free_range);
--
2.49.0.rc1.451.g8f38331e32-goog
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