| Message ID | 1540551662-26458-5-git-send-email-arunks@codeaurora.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | mm: convert totalram_pages, totalhigh_pages and managed pages to atomic | expand |
[for some reason I have dropped the rest of the cc list. Restored] On Tue 06-11-18 15:17:32, Michal Hocko wrote: > On Fri 26-10-18 16:31:02, Arun KS wrote: > > Now totalram_pages and managed_pages are atomic varibles. No need > > of managed_page_count spinlock. > > Yes this is the real improvement. The lock had really a weak consistency > guarantee. It hasn't been used for anything but the update but no reader > actually cares about all the values being updated to be in sync. I > haven't really done an excavation work to see whether it used to be used > in other contexts in the past but it simply doesn't have any meaning > anymore. > > > Signed-off-by: Arun KS <arunks@codeaurora.org> > > Acked-by: Michal Hocko <mhocko@suse.com> > > Thanks for getting through all the hassles to reach to this end point. > > > --- > > include/linux/mmzone.h | 6 ------ > > mm/page_alloc.c | 5 ----- > > 2 files changed, 11 deletions(-) > > > > diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h > > index 597b0c7..aa960f6 100644 > > --- a/include/linux/mmzone.h > > +++ b/include/linux/mmzone.h > > @@ -428,12 +428,6 @@ struct zone { > > * Write access to present_pages at runtime should be protected by > > * mem_hotplug_begin/end(). Any reader who can't tolerant drift of > > * present_pages should get_online_mems() to get a stable value. > > - * > > - * Read access to managed_pages should be safe because it's unsigned > > - * long. Write access to zone->managed_pages and totalram_pages are > > - * protected by managed_page_count_lock at runtime. Idealy only > > - * adjust_managed_page_count() should be used instead of directly > > - * touching zone->managed_pages and totalram_pages. > > */ > > atomic_long_t managed_pages; > > unsigned long spanned_pages; > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > > index af832de..e29e78f 100644 > > --- a/mm/page_alloc.c > > +++ b/mm/page_alloc.c > > @@ -122,9 +122,6 @@ > > }; > > EXPORT_SYMBOL(node_states); > > > > -/* Protect totalram_pages and zone->managed_pages */ > > -static DEFINE_SPINLOCK(managed_page_count_lock); > > - > > atomic_long_t _totalram_pages __read_mostly; > > unsigned long totalreserve_pages __read_mostly; > > unsigned long totalcma_pages __read_mostly; > > @@ -7062,14 +7059,12 @@ static int __init cmdline_parse_movablecore(char *p) > > > > void adjust_managed_page_count(struct page *page, long count) > > { > > - spin_lock(&managed_page_count_lock); > > atomic_long_add(count, &page_zone(page)->managed_pages); > > totalram_pages_add(count); > > #ifdef CONFIG_HIGHMEM > > if (PageHighMem(page)) > > totalhigh_pages_add(count); > > #endif > > - spin_unlock(&managed_page_count_lock); > > } > > EXPORT_SYMBOL(adjust_managed_page_count); > > > > -- > > 1.9.1 > > -- > Michal Hocko > SUSE Labs
On 10/26/18 1:01 PM, Arun KS wrote: > Now totalram_pages and managed_pages are atomic varibles. No need > of managed_page_count spinlock. > > Signed-off-by: Arun KS <arunks@codeaurora.org> Acked-by: Vlastimil Babka <vbabka@suse.cz> > --- > include/linux/mmzone.h | 6 ------ > mm/page_alloc.c | 5 ----- > 2 files changed, 11 deletions(-) > > diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h > index 597b0c7..aa960f6 100644 > --- a/include/linux/mmzone.h > +++ b/include/linux/mmzone.h > @@ -428,12 +428,6 @@ struct zone { > * Write access to present_pages at runtime should be protected by > * mem_hotplug_begin/end(). Any reader who can't tolerant drift of > * present_pages should get_online_mems() to get a stable value. > - * > - * Read access to managed_pages should be safe because it's unsigned > - * long. Write access to zone->managed_pages and totalram_pages are > - * protected by managed_page_count_lock at runtime. Idealy only > - * adjust_managed_page_count() should be used instead of directly > - * touching zone->managed_pages and totalram_pages. > */ > atomic_long_t managed_pages; > unsigned long spanned_pages; > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index af832de..e29e78f 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -122,9 +122,6 @@ > }; > EXPORT_SYMBOL(node_states); > > -/* Protect totalram_pages and zone->managed_pages */ > -static DEFINE_SPINLOCK(managed_page_count_lock); > - > atomic_long_t _totalram_pages __read_mostly; > unsigned long totalreserve_pages __read_mostly; > unsigned long totalcma_pages __read_mostly; > @@ -7062,14 +7059,12 @@ static int __init cmdline_parse_movablecore(char *p) > > void adjust_managed_page_count(struct page *page, long count) > { > - spin_lock(&managed_page_count_lock); > atomic_long_add(count, &page_zone(page)->managed_pages); > totalram_pages_add(count); > #ifdef CONFIG_HIGHMEM > if (PageHighMem(page)) > totalhigh_pages_add(count); > #endif > - spin_unlock(&managed_page_count_lock); > } > EXPORT_SYMBOL(adjust_managed_page_count); > >
diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h index 597b0c7..aa960f6 100644 --- a/include/linux/mmzone.h +++ b/include/linux/mmzone.h @@ -428,12 +428,6 @@ struct zone { * Write access to present_pages at runtime should be protected by * mem_hotplug_begin/end(). Any reader who can't tolerant drift of * present_pages should get_online_mems() to get a stable value. - * - * Read access to managed_pages should be safe because it's unsigned - * long. Write access to zone->managed_pages and totalram_pages are - * protected by managed_page_count_lock at runtime. Idealy only - * adjust_managed_page_count() should be used instead of directly - * touching zone->managed_pages and totalram_pages. */ atomic_long_t managed_pages; unsigned long spanned_pages; diff --git a/mm/page_alloc.c b/mm/page_alloc.c index af832de..e29e78f 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -122,9 +122,6 @@ }; EXPORT_SYMBOL(node_states); -/* Protect totalram_pages and zone->managed_pages */ -static DEFINE_SPINLOCK(managed_page_count_lock); - atomic_long_t _totalram_pages __read_mostly; unsigned long totalreserve_pages __read_mostly; unsigned long totalcma_pages __read_mostly; @@ -7062,14 +7059,12 @@ static int __init cmdline_parse_movablecore(char *p) void adjust_managed_page_count(struct page *page, long count) { - spin_lock(&managed_page_count_lock); atomic_long_add(count, &page_zone(page)->managed_pages); totalram_pages_add(count); #ifdef CONFIG_HIGHMEM if (PageHighMem(page)) totalhigh_pages_add(count); #endif - spin_unlock(&managed_page_count_lock); } EXPORT_SYMBOL(adjust_managed_page_count);
Now totalram_pages and managed_pages are atomic varibles. No need of managed_page_count spinlock. Signed-off-by: Arun KS <arunks@codeaurora.org> --- include/linux/mmzone.h | 6 ------ mm/page_alloc.c | 5 ----- 2 files changed, 11 deletions(-)