From 704503d836042d4a4c7685b7036e7de0418fbc0f Mon Sep 17 00:00:00 2001 From: Alexey Dobriyan Date: Tue, 31 Mar 2009 15:23:18 -0700 Subject: [PATCH] mm: fix proc_dointvec_userhz_jiffies "breakage" Addresses http://bugzilla.kernel.org/show_bug.cgi?id=9838 On i386, HZ=1000, jiffies_to_clock_t() converts time in a somewhat strange way from the user's point of view: # echo 500 >/proc/sys/vm/dirty_writeback_centisecs # cat /proc/sys/vm/dirty_writeback_centisecs 499 So, we have 5000 jiffies converted to only 499 clock ticks and reported back. TICK_NSEC = 999848 ACTHZ = 256039 Keeping in-kernel variable in units passed from userspace will fix issue of course, but this probably won't be right for every sysctl. [akpm@linux-foundation.org: coding-style fixes] Signed-off-by: Alexey Dobriyan Cc: Peter Zijlstra Cc: Nick Piggin Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/writeback.h | 4 ++-- kernel/sysctl.c | 2 +- mm/page-writeback.c | 20 +++++++++++--------- 3 files changed, 14 insertions(+), 12 deletions(-) diff --git a/include/linux/writeback.h b/include/linux/writeback.h index 7300ecdc480..93445477f86 100644 --- a/include/linux/writeback.h +++ b/include/linux/writeback.h @@ -109,8 +109,8 @@ extern int dirty_background_ratio; extern unsigned long dirty_background_bytes; extern int vm_dirty_ratio; extern unsigned long vm_dirty_bytes; -extern int dirty_writeback_interval; -extern int dirty_expire_interval; +extern unsigned int dirty_writeback_interval; +extern unsigned int dirty_expire_interval; extern int vm_highmem_is_dirtyable; extern int block_dump; extern int laptop_mode; diff --git a/kernel/sysctl.c b/kernel/sysctl.c index c5ef44ff850..2e490a389dd 100644 --- a/kernel/sysctl.c +++ b/kernel/sysctl.c @@ -1010,7 +1010,7 @@ static struct ctl_table vm_table[] = { .data = &dirty_expire_interval, .maxlen = sizeof(dirty_expire_interval), .mode = 0644, - .proc_handler = &proc_dointvec_userhz_jiffies, + .proc_handler = &proc_dointvec, }, { .ctl_name = VM_NR_PDFLUSH_THREADS, diff --git a/mm/page-writeback.c b/mm/page-writeback.c index 6aa92b03c74..30351f0063a 100644 --- a/mm/page-writeback.c +++ b/mm/page-writeback.c @@ -92,14 +92,14 @@ int vm_dirty_ratio = 20; unsigned long vm_dirty_bytes; /* - * The interval between `kupdate'-style writebacks, in jiffies + * The interval between `kupdate'-style writebacks */ -int dirty_writeback_interval = 5 * HZ; +unsigned int dirty_writeback_interval = 5 * 100; /* sentiseconds */ /* - * The longest number of jiffies for which data is allowed to remain dirty + * The longest time for which data is allowed to remain dirty */ -int dirty_expire_interval = 30 * HZ; +unsigned int dirty_expire_interval = 30 * 100; /* sentiseconds */ /* * Flag that makes the machine dump writes/reads and block dirtyings. @@ -770,9 +770,9 @@ static void wb_kupdate(unsigned long arg) sync_supers(); - oldest_jif = jiffies - dirty_expire_interval; + oldest_jif = jiffies - msecs_to_jiffies(dirty_expire_interval); start_jif = jiffies; - next_jif = start_jif + dirty_writeback_interval; + next_jif = start_jif + msecs_to_jiffies(dirty_writeback_interval * 10); nr_to_write = global_page_state(NR_FILE_DIRTY) + global_page_state(NR_UNSTABLE_NFS) + (inodes_stat.nr_inodes - inodes_stat.nr_unused); @@ -801,9 +801,10 @@ static void wb_kupdate(unsigned long arg) int dirty_writeback_centisecs_handler(ctl_table *table, int write, struct file *file, void __user *buffer, size_t *length, loff_t *ppos) { - proc_dointvec_userhz_jiffies(table, write, file, buffer, length, ppos); + proc_dointvec(table, write, file, buffer, length, ppos); if (dirty_writeback_interval) - mod_timer(&wb_timer, jiffies + dirty_writeback_interval); + mod_timer(&wb_timer, jiffies + + msecs_to_jiffies(dirty_writeback_interval * 10)); else del_timer(&wb_timer); return 0; @@ -905,7 +906,8 @@ void __init page_writeback_init(void) { int shift; - mod_timer(&wb_timer, jiffies + dirty_writeback_interval); + mod_timer(&wb_timer, + jiffies + msecs_to_jiffies(dirty_writeback_interval * 10)); writeback_set_ratelimit(); register_cpu_notifier(&ratelimit_nb);