> -----Original Message----- > From: Andrew Morton [mailto:a...@linux-foundation.org] > Sent: Thursday, March 19, 2015 6:08 AM > To: Wang, Yalin > Cc: 'David Rientjes'; 'heiko.carst...@de.ibm.com'; 't...@linutronix.de'; > 'linux-kernel@vger.kernel.org' > Subject: Re: [RFC V2] proc: change /proc/stat show > > On Wed, 18 Mar 2015 10:35:39 +0800 "Wang, Yalin" > <yalin.w...@sonymobile.com> wrote: > > > This patch change /proc/stat to show each cpu, > > we show each present cpus instead of eacn online cpu, > > because some cpus are online / offline dynamically, > > we should also show its cputime even it is offline, > > some lib will read this file to detect cpu numbers, > > we should also return the real present cpu numbers, > > not just online cpus. > > /proc/cpuinfo also skips offline CPUs. > > > --- a/fs/proc/stat.c > > +++ b/fs/proc/stat.c > > @@ -130,7 +130,7 @@ static int show_stat(struct seq_file *p, void *v) > > seq_put_decimal_ull(p, ' ', cputime64_to_clock_t(guest_nice)); > > seq_putc(p, '\n'); > > > > - for_each_online_cpu(i) { > > + for_each_present_cpu(i) { > > /* Copy values here to work around gcc-2.95.3, gcc-2.96 */ > > user = kcpustat_cpu(i).cpustat[CPUTIME_USER]; > > nice = kcpustat_cpu(i).cpustat[CPUTIME_NICE]; > > It's a non-back-compatible userspace interface change and I don't know > what might break as a result. For example, anyone who is using > /proc/stat to find out which CPUs are online will get a surprise! > I see, I found on android, sysconf(_SC_NPROCESSORS_ONLN) function is implemented by read /proc/stat file, and return the online processor numbers, it will be non-compatible if I change this.
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