forked from luck/tmp_suning_uos_patched
365e9c87a9
update_mem_hiwater has attracted various criticisms, in particular from those concerned with mm scalability. Originally it was called whenever rss or total_vm got raised. Then many of those callsites were replaced by a timer tick call from account_system_time. Now Frank van Maarseveen reports that to be found inadequate. How about this? Works for Frank. Replace update_mem_hiwater, a poor combination of two unrelated ops, by macros update_hiwater_rss and update_hiwater_vm. Don't attempt to keep mm->hiwater_rss up to date at timer tick, nor every time we raise rss (usually by 1): those are hot paths. Do the opposite, update only when about to lower rss (usually by many), or just before final accounting in do_exit. Handle mm->hiwater_vm in the same way, though it's much less of an issue. Demand that whoever collects these hiwater statistics do the work of taking the maximum with rss or total_vm. And there has been no collector of these hiwater statistics in the tree. The new convention needs an example, so match Frank's usage by adding a VmPeak line above VmSize to /proc/<pid>/status, and also a VmHWM line above VmRSS (High-Water-Mark or High-Water-Memory). There was a particular anomaly during mremap move, that hiwater_vm might be captured too high. A fleeting such anomaly remains, but it's quickly corrected now, whereas before it would stick. What locking? None: if the app is racy then these statistics will be racy, it's not worth any overhead to make them exact. But whenever it suits, hiwater_vm is updated under exclusive mmap_sem, and hiwater_rss under page_table_lock (for now) or with preemption disabled (later on): without going to any trouble, minimize the time between reading current values and updating, to minimize those occasions when a racing thread bumps a count up and back down in between. Signed-off-by: Hugh Dickins <hugh@veritas.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org> |
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.. | ||
irq | ||
power | ||
acct.c | ||
audit.c | ||
auditsc.c | ||
capability.c | ||
compat.c | ||
configs.c | ||
cpu.c | ||
cpuset.c | ||
crash_dump.c | ||
dma.c | ||
exec_domain.c | ||
exit.c | ||
extable.c | ||
fork.c | ||
futex.c | ||
intermodule.c | ||
itimer.c | ||
kallsyms.c | ||
Kconfig.hz | ||
Kconfig.preempt | ||
kexec.c | ||
kfifo.c | ||
kmod.c | ||
kprobes.c | ||
ksysfs.c | ||
kthread.c | ||
Makefile | ||
module.c | ||
panic.c | ||
params.c | ||
pid.c | ||
posix-cpu-timers.c | ||
posix-timers.c | ||
printk.c | ||
profile.c | ||
ptrace.c | ||
rcupdate.c | ||
resource.c | ||
sched.c | ||
seccomp.c | ||
signal.c | ||
softirq.c | ||
softlockup.c | ||
spinlock.c | ||
stop_machine.c | ||
sys_ni.c | ||
sys.c | ||
sysctl.c | ||
time.c | ||
timer.c | ||
uid16.c | ||
user.c | ||
wait.c | ||
workqueue.c |