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mm: reference totalram_pages and managed_pages once per function

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Patch series "mm: convert totalram_pages, totalhigh_pages and managed
pages to atomic", v5.

This series converts totalram_pages, totalhigh_pages and
zone->managed_pages to atomic variables.

totalram_pages, zone->managed_pages and totalhigh_pages updates are
protected by managed_page_count_lock, but readers never care about it.
Convert these variables to atomic to avoid readers potentially seeing a
store tear.

Main motivation was that managed_page_count_lock handling was complicating
things.  It was discussed in length here,
https://lore.kernel.org/patchwork/patch/995739/#1181785 It seemes better
to remove the lock and convert variables to atomic.  With the change,
preventing poteintial store-to-read tearing comes as a bonus.

This patch (of 4):

This 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.

Link: http://lkml.kernel.org/r/1542090790-21750-2-git-send-email-arunks@codeaurora.org
Signed-off-by: Arun KS <arunks@codeaurora.org>
Reviewed-by: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
Reviewed-by: David Hildenbrand <david@redhat.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Reviewed-by: Pavel Tatashin <pasha.tatashin@soleen.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Arun KS 2018-12-28 00:34:20 -08:00 committed by Linus Torvalds
parent fecd4a50ba
commit 3d6357de8a
12 changed files with 44 additions and 33 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
arch/um/kernel/mem.c
View File

@ -52,7 +52,7 @@ 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;
mem_init_print_info(NULL);
kmalloc_ok = 1;
}

5
arch/x86/kernel/cpu/microcode/core.c
View File

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

19
drivers/hv/hv_balloon.c
View File

@ -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 nr_pages = 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 (nr_pages < MB2PAGES(128))
min_pages = MB2PAGES(8) + (nr_pages >> 1);
else if (nr_pages < MB2PAGES(512))
min_pages = MB2PAGES(40) + (nr_pages >> 2);
else if (nr_pages < MB2PAGES(2048))
min_pages = MB2PAGES(104) + (nr_pages >> 3);
else if (nr_pages < MB2PAGES(8192))
min_pages = MB2PAGES(232) + (nr_pages >> 4);
else
min_pages = MB2PAGES(488) + (totalram_pages >> 5);
min_pages = MB2PAGES(488) + (nr_pages >> 5);
#undef MB2PAGES
return min_pages;
}

7
fs/file_table.c
View File

@ -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 nr_pages = totalram_pages;
unsigned long memreserve = (nr_pages - nr_free_pages()) * 3/2;
memreserve = min(memreserve, totalram_pages - 1);
n = ((totalram_pages - memreserve) * (PAGE_SIZE / 1024)) / 10;
memreserve = min(memreserve, nr_pages - 1);
n = ((nr_pages - memreserve) * (PAGE_SIZE / 1024)) / 10;
files_stat.max_files = max_t(unsigned long, n, NR_FILE);
}

5
kernel/fork.c
View File

@ -744,15 +744,16 @@ void __init __weak arch_task_cache_init(void) { }
static void set_max_threads(unsigned int max_threads_suggested)
{
u64 threads;
unsigned long nr_pages = 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(nr_pages) + fls64(PAGE_SIZE) > 64)
threads = MAX_THREADS;
else
threads = div64_u64((u64) totalram_pages * (u64) PAGE_SIZE,
threads = div64_u64((u64) nr_pages * (u64) PAGE_SIZE,
(u64) THREAD_SIZE * 8UL);
if (threads > max_threads_suggested)

5
kernel/kexec_core.c
View File

@ -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 nr_pages = 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) > nr_pages / 2)
return -EINVAL;
total_pages += PAGE_COUNT(image->segment[i].memsz);
}
if (total_pages > totalram_pages / 2)
if (total_pages > nr_pages / 2)
return -EINVAL;
/*

5
mm/page_alloc.c
View File

@ -7257,6 +7257,7 @@ 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++) {
@ -7267,8 +7268,8 @@ 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;

3
mm/shmem.c
View File

@ -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 nr_pages = totalram_pages;
return min(nr_pages - totalhigh_pages, nr_pages / 2);
}
#endif

7
net/dccp/proto.c
View File

@ -1131,6 +1131,7 @@ EXPORT_SYMBOL_GPL(dccp_debug);
static int __init dccp_init(void)
{
unsigned long goal;
unsigned long nr_pages = totalram_pages;
int ehash_order, bhash_order, i;
int rc;
@ -1157,10 +1158,10 @@ 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 (nr_pages >= (128 * 1024))
goal = nr_pages >> (21 - PAGE_SHIFT);
else
goal = totalram_pages >> (23 - PAGE_SHIFT);
goal = nr_pages >> (23 - PAGE_SHIFT);
if (thash_entries)
goal = (thash_entries *

7
net/netfilter/nf_conntrack_core.c
View File

@ -2248,6 +2248,7 @@ static __always_inline unsigned int total_extension_size(void)
int nf_conntrack_init_start(void)
{
unsigned long nr_pages = totalram_pages;
int max_factor = 8;
int ret = -ENOMEM;
int i;
@ -2267,11 +2268,11 @@ int nf_conntrack_init_start(void)
* >= 4GB machines have 65536 buckets.
*/
nf_conntrack_htable_size
= (((totalram_pages << PAGE_SHIFT) / 16384)
= (((nr_pages << PAGE_SHIFT) / 16384)
/ sizeof(struct hlist_head));
if (totalram_pages > (4 * (1024 * 1024 * 1024 / PAGE_SIZE)))
if (nr_pages > (4 * (1024 * 1024 * 1024 / PAGE_SIZE)))
nf_conntrack_htable_size = 65536;
else if (totalram_pages > (1024 * 1024 * 1024 / PAGE_SIZE))
else if (nr_pages > (1024 * 1024 * 1024 / PAGE_SIZE))
nf_conntrack_htable_size = 16384;
if (nf_conntrack_htable_size < 32)
nf_conntrack_htable_size = 32;

5
net/netfilter/xt_hashlimit.c
View File

@ -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 nr_pages = totalram_pages;
int ret;
if (cfg->size) {
size = cfg->size;
} else {
size = (totalram_pages << PAGE_SHIFT) / 16384 /
size = (nr_pages << PAGE_SHIFT) / 16384 /
sizeof(struct hlist_head);
if (totalram_pages > 1024 * 1024 * 1024 / PAGE_SIZE)
if (nr_pages > 1024 * 1024 * 1024 / PAGE_SIZE)
size = 8192;
if (size < 16)
size = 16;

7
net/sctp/protocol.c
View File

@ -1368,6 +1368,7 @@ static __init int sctp_init(void)
int status = -EINVAL;
unsigned long goal;
unsigned long limit;
unsigned long nr_pages = 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 (nr_pages >= (128 * 1024))
goal = nr_pages >> (22 - PAGE_SHIFT);
else
goal = totalram_pages >> (24 - PAGE_SHIFT);
goal = nr_pages >> (24 - PAGE_SHIFT);
/* Then compute the page order for said goal */
order = get_order(goal);