[PATCH v4 1/4] mm: reference totalram_pages and managed_pages once per function

From: Arun KS
Date: Mon Nov 12 2018 - 01:08:26 EST

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This patch is in preparation to a later patch which converts totalram_pages
and zone->managed_pages to atomic variables. Please note that re-reading
the value might lead to a different value and as such it could lead to
unexpected behavior. There are no known bugs as a result of the current code
but it is better to prevent from them in principle.

Signed-off-by: Arun KS <arunks@xxxxxxxxxxxxxx>
Reviewed-by: Konstantin Khlebnikov <khlebnikov@xxxxxxxxxxxxxx>
Acked-by: Michal Hocko <mhocko@xxxxxxxx>
Acked-by: Vlastimil Babka <vbabka@xxxxxxx>
---
arch/um/kernel/mem.c | 3 +--
arch/x86/kernel/cpu/microcode/core.c | 5 +++--
drivers/hv/hv_balloon.c | 19 ++++++++++---------
fs/file_table.c | 7 ++++---
kernel/fork.c | 5 +++--
kernel/kexec_core.c | 5 +++--
mm/page_alloc.c | 5 +++--
mm/shmem.c | 3 ++-
net/dccp/proto.c | 7 ++++---
net/netfilter/nf_conntrack_core.c | 7 ++++---
net/netfilter/xt_hashlimit.c | 5 +++--
net/sctp/protocol.c | 7 ++++---
12 files changed, 44 insertions(+), 34 deletions(-)

diff --git a/arch/um/kernel/mem.c b/arch/um/kernel/mem.c
index 1067469..134d3fd 100644
--- a/arch/um/kernel/mem.c
+++ b/arch/um/kernel/mem.c
@@ -51,8 +51,7 @@ void __init mem_init(void)

/* this will put all low memory onto the freelists */
memblock_free_all();
- max_low_pfn = totalram_pages;
- max_pfn = totalram_pages;
+ max_pfn = max_low_pfn = totalram_pages;
mem_init_print_info(NULL);
kmalloc_ok = 1;
}
diff --git a/arch/x86/kernel/cpu/microcode/core.c b/arch/x86/kernel/cpu/microcode/core.c
index 2637ff0..99c67ca 100644
--- a/arch/x86/kernel/cpu/microcode/core.c
+++ b/arch/x86/kernel/cpu/microcode/core.c
@@ -434,9 +434,10 @@ static ssize_t microcode_write(struct file *file, const char __user *buf,
size_t len, loff_t *ppos)
{
ssize_t ret = -EINVAL;
+ unsigned long totalram_pgs = totalram_pages;

- if ((len >> PAGE_SHIFT) > totalram_pages) {
- pr_err("too much data (max %ld pages)\n", totalram_pages);
+ if ((len >> PAGE_SHIFT) > totalram_pgs) {
+ pr_err("too much data (max %ld pages)\n", totalram_pgs);
return ret;
}

diff --git a/drivers/hv/hv_balloon.c b/drivers/hv/hv_balloon.c
index 4163151..cac4945 100644
--- a/drivers/hv/hv_balloon.c
+++ b/drivers/hv/hv_balloon.c
@@ -1090,6 +1090,7 @@ static void process_info(struct hv_dynmem_device *dm, struct dm_info_msg *msg)
static unsigned long compute_balloon_floor(void)
{
unsigned long min_pages;
+ unsigned long totalram_pgs = totalram_pages;
#define MB2PAGES(mb) ((mb) << (20 - PAGE_SHIFT))
/* Simple continuous piecewiese linear function:
* max MiB -> min MiB gradient
@@ -1102,16 +1103,16 @@ static unsigned long compute_balloon_floor(void)
* 8192 744 (1/16)
* 32768 1512 (1/32)
*/
- if (totalram_pages < MB2PAGES(128))
- min_pages = MB2PAGES(8) + (totalram_pages >> 1);
- else if (totalram_pages < MB2PAGES(512))
- min_pages = MB2PAGES(40) + (totalram_pages >> 2);
- else if (totalram_pages < MB2PAGES(2048))
- min_pages = MB2PAGES(104) + (totalram_pages >> 3);
- else if (totalram_pages < MB2PAGES(8192))
- min_pages = MB2PAGES(232) + (totalram_pages >> 4);
+ if (totalram_pgs < MB2PAGES(128))
+ min_pages = MB2PAGES(8) + (totalram_pgs >> 1);
+ else if (totalram_pgs < MB2PAGES(512))
+ min_pages = MB2PAGES(40) + (totalram_pgs >> 2);
+ else if (totalram_pgs < MB2PAGES(2048))
+ min_pages = MB2PAGES(104) + (totalram_pgs >> 3);
+ else if (totalram_pgs < MB2PAGES(8192))
+ min_pages = MB2PAGES(232) + (totalram_pgs >> 4);
else
- min_pages = MB2PAGES(488) + (totalram_pages >> 5);
+ min_pages = MB2PAGES(488) + (totalram_pgs >> 5);
#undef MB2PAGES
return min_pages;
}
diff --git a/fs/file_table.c b/fs/file_table.c
index e49af4c..6e3c088 100644
--- a/fs/file_table.c
+++ b/fs/file_table.c
@@ -380,10 +380,11 @@ void __init files_init(void)
void __init files_maxfiles_init(void)
{
unsigned long n;
- unsigned long memreserve = (totalram_pages - nr_free_pages()) * 3/2;
+ unsigned long totalram_pgs = totalram_pages;
+ unsigned long memreserve = (totalram_pgs - nr_free_pages()) * 3/2;

- memreserve = min(memreserve, totalram_pages - 1);
- n = ((totalram_pages - memreserve) * (PAGE_SIZE / 1024)) / 10;
+ memreserve = min(memreserve, totalram_pgs - 1);
+ n = ((totalram_pgs - memreserve) * (PAGE_SIZE / 1024)) / 10;

files_stat.max_files = max_t(unsigned long, n, NR_FILE);
}
diff --git a/kernel/fork.c b/kernel/fork.c
index 07cddff..7823f31 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -739,15 +739,16 @@ void __init __weak arch_task_cache_init(void) { }
static void set_max_threads(unsigned int max_threads_suggested)
{
u64 threads;
+ unsigned long totalram_pgs = totalram_pages;

/*
* The number of threads shall be limited such that the thread
* structures may only consume a small part of the available memory.
*/
- if (fls64(totalram_pages) + fls64(PAGE_SIZE) > 64)
+ if (fls64(totalram_pgs) + fls64(PAGE_SIZE) > 64)
threads = MAX_THREADS;
else
- threads = div64_u64((u64) totalram_pages * (u64) PAGE_SIZE,
+ threads = div64_u64((u64) totalram_pgs * (u64) PAGE_SIZE,
(u64) THREAD_SIZE * 8UL);

if (threads > max_threads_suggested)
diff --git a/kernel/kexec_core.c b/kernel/kexec_core.c
index 86ef06d..dff217c 100644
--- a/kernel/kexec_core.c
+++ b/kernel/kexec_core.c
@@ -152,6 +152,7 @@ int sanity_check_segment_list(struct kimage *image)
int i;
unsigned long nr_segments = image->nr_segments;
unsigned long total_pages = 0;
+ unsigned long totalram_pgs = totalram_pages;

/*
* Verify we have good destination addresses. The caller is
@@ -217,13 +218,13 @@ int sanity_check_segment_list(struct kimage *image)
* wasted allocating pages, which can cause a soft lockup.
*/
for (i = 0; i < nr_segments; i++) {
- if (PAGE_COUNT(image->segment[i].memsz) > totalram_pages / 2)
+ if (PAGE_COUNT(image->segment[i].memsz) > totalram_pgs / 2)
return -EINVAL;

total_pages += PAGE_COUNT(image->segment[i].memsz);
}

- if (total_pages > totalram_pages / 2)
+ if (total_pages > totalram_pgs / 2)
return -EINVAL;

/*
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index a919ba5..173312b 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -7245,6 +7245,7 @@ static void calculate_totalreserve_pages(void)
for (i = 0; i < MAX_NR_ZONES; i++) {
struct zone *zone = pgdat->node_zones + i;
long max = 0;
+ unsigned long managed_pages = zone->managed_pages;

/* Find valid and maximum lowmem_reserve in the zone */
for (j = i; j < MAX_NR_ZONES; j++) {
@@ -7255,8 +7256,8 @@ static void calculate_totalreserve_pages(void)
/* we treat the high watermark as reserved pages. */
max += high_wmark_pages(zone);

- if (max > zone->managed_pages)
- max = zone->managed_pages;
+ if (max > managed_pages)
+ max = managed_pages;

pgdat->totalreserve_pages += max;

diff --git a/mm/shmem.c b/mm/shmem.c
index ea26d7a..6b91eab 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -114,7 +114,8 @@ static unsigned long shmem_default_max_blocks(void)

static unsigned long shmem_default_max_inodes(void)
{
- return min(totalram_pages - totalhigh_pages, totalram_pages / 2);
+ unsigned long totalram_pgs = totalram_pages;
+ return min(totalram_pgs - totalhigh_pages, totalram_pgs / 2);
}
#endif

diff --git a/net/dccp/proto.c b/net/dccp/proto.c
index 43733ac..f27daa1 100644
--- a/net/dccp/proto.c
+++ b/net/dccp/proto.c
@@ -1131,6 +1131,7 @@ static inline void dccp_mib_exit(void)
static int __init dccp_init(void)
{
unsigned long goal;
+ unsigned long totalram_pgs = totalram_pages;
int ehash_order, bhash_order, i;
int rc;

@@ -1154,10 +1155,10 @@ static int __init dccp_init(void)
*
* The methodology is similar to that of the buffer cache.
*/
- if (totalram_pages >= (128 * 1024))
- goal = totalram_pages >> (21 - PAGE_SHIFT);
+ if (totalram_pgs >= (128 * 1024))
+ goal = totalram_pgs >> (21 - PAGE_SHIFT);
else
- goal = totalram_pages >> (23 - PAGE_SHIFT);
+ goal = totalram_pgs >> (23 - PAGE_SHIFT);

if (thash_entries)
goal = (thash_entries *
diff --git a/net/netfilter/nf_conntrack_core.c b/net/netfilter/nf_conntrack_core.c
index e92e749..cd233f6 100644
--- a/net/netfilter/nf_conntrack_core.c
+++ b/net/netfilter/nf_conntrack_core.c
@@ -2251,6 +2251,7 @@ static __always_inline unsigned int total_extension_size(void)

int nf_conntrack_init_start(void)
{
+ unsigned long totalram_pgs = totalram_pages;
int max_factor = 8;
int ret = -ENOMEM;
int i;
@@ -2270,11 +2271,11 @@ int nf_conntrack_init_start(void)
* >= 4GB machines have 65536 buckets.
*/
nf_conntrack_htable_size
- = (((totalram_pages << PAGE_SHIFT) / 16384)
+ = (((totalram_pgs << PAGE_SHIFT) / 16384)
/ sizeof(struct hlist_head));
- if (totalram_pages > (4 * (1024 * 1024 * 1024 / PAGE_SIZE)))
+ if (totalram_pgs > (4 * (1024 * 1024 * 1024 / PAGE_SIZE)))
nf_conntrack_htable_size = 65536;
- else if (totalram_pages > (1024 * 1024 * 1024 / PAGE_SIZE))
+ else if (totalram_pgs > (1024 * 1024 * 1024 / PAGE_SIZE))
nf_conntrack_htable_size = 16384;
if (nf_conntrack_htable_size < 32)
nf_conntrack_htable_size = 32;
diff --git a/net/netfilter/xt_hashlimit.c b/net/netfilter/xt_hashlimit.c
index 3e7d259..6cb9a74 100644
--- a/net/netfilter/xt_hashlimit.c
+++ b/net/netfilter/xt_hashlimit.c
@@ -274,14 +274,15 @@ static int htable_create(struct net *net, struct hashlimit_cfg3 *cfg,
struct xt_hashlimit_htable *hinfo;
const struct seq_operations *ops;
unsigned int size, i;
+ unsigned long totalram_pgs = totalram_pages;
int ret;

if (cfg->size) {
size = cfg->size;
} else {
- size = (totalram_pages << PAGE_SHIFT) / 16384 /
+ size = (totalram_pgs << PAGE_SHIFT) / 16384 /
sizeof(struct hlist_head);
- if (totalram_pages > 1024 * 1024 * 1024 / PAGE_SIZE)
+ if (totalram_pgs > 1024 * 1024 * 1024 / PAGE_SIZE)
size = 8192;
if (size < 16)
size = 16;
diff --git a/net/sctp/protocol.c b/net/sctp/protocol.c
index 9b277bd..aacae17 100644
--- a/net/sctp/protocol.c
+++ b/net/sctp/protocol.c
@@ -1368,6 +1368,7 @@ static __init int sctp_init(void)
int status = -EINVAL;
unsigned long goal;
unsigned long limit;
+ unsigned long totalram_pgs = totalram_pages;
int max_share;
int order;
int num_entries;
@@ -1426,10 +1427,10 @@ static __init int sctp_init(void)
* The methodology is similar to that of the tcp hash tables.
* Though not identical. Start by getting a goal size
*/
- if (totalram_pages >= (128 * 1024))
- goal = totalram_pages >> (22 - PAGE_SHIFT);
+ if (totalram_pgs >= (128 * 1024))
+ goal = totalram_pgs >> (22 - PAGE_SHIFT);
else
- goal = totalram_pages >> (24 - PAGE_SHIFT);
+ goal = totalram_pgs >> (24 - PAGE_SHIFT);

/* Then compute the page order for said goal */
order = get_order(goal);
--
1.9.1

Next message: Corentin Labbe: "Re: [GIT PULL] ARM: SoC fixes"
Previous message: Arun KS: "[PATCH v4 3/4] mm: convert totalram_pages and totalhigh_pages variables to atomic"
In reply to: Arun KS: "[PATCH v4 3/4] mm: convert totalram_pages and totalhigh_pages variables to atomic"
Next in thread: Matthew Wilcox: "Re: [PATCH v4 1/4] mm: reference totalram_pages and managed_pages once per function"
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