On Mon, Oct 31, 2011 at 5:00 PM, Chen Jie <chenj@xxxxxxxxxx> wrote: > Hi all, > > On MIPS, with maxsec=4, clocks_calc_mult_shift() may generate a very > big mult, which may easily cause timekeeper.mult overflow within > timekeeping jobs. Hmmm, why not use clocksource_register_hz()/clocksource_register_khz() instead? it's more convenient. Thanks, Yong > > e.g. when clock freq was 250000500(i.e. mips_hpt_frequency=250000500, > and the CPU Freq will be 250000500*2=500001000), mult will be > 0xffffde72 > > Attachment is a script that calculates mult values for CPU Freq > between 400050000 and 500050000, with 1KHz step. It outputs mult > values greater than 0xf0000000: > CPU Freq:500001000, mult:0xffffde72, shift:30 > CPU Freq:500002000, mult:0xffffbce4, shift:30 > CPU Freq:500003000, mult:0xffff9b56, shift:30 > CPU Freq:500004000, mult:0xffff79c9, shift:30 > ... > > The peak value appears around CPU_freq=500001000. > > To avoid this, it may need: > 1. Supply a bigger maxsec value? > 2. In clocks_calc_mult_shift(), pick next mult/shift pair if mult is > too big? Then maxsec will not be strictly obeyed. > 3. Change timekeeper.mult to u64? > 4. ... > > Any idea? > > > > -- > Regards, > - Chen Jie > -- Only stand for myself
