Messages in this thread | | | From | "Luis R. Rodriguez" <> | Date | Fri, 13 Jun 2014 15:05:59 -0700 | Subject | Re: [PATCH v3] printk: allow increasing the ring buffer depending on the number of CPUs |
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On Fri, Jun 13, 2014 at 2:41 PM, Davidlohr Bueso <davidlohr@hp.com> wrote: > On Fri, 2014-06-13 at 11:28 -0700, Luis R. Rodriguez wrote: >> + /* >> + * If you set log_buf_len=n kernel parameter LOG_CPU_MIN_BUF_SHIFT will >> + * be ignored. LOG_CPU_MIN_BUF_SHIFT is a proactive measure for large >> + * systems. With a LOG_BUF_SHIFT of 18 and LOG_CPU_MIN_BUF_SHIFT 12 at >> + * we'd require more than 64 CPUs to trigger an increase from the >> + * default. >> + */ >> + if (!new_log_buf_len && (cpu_extra > __LOG_BUF_LEN / 2)) > ^ that ! looks wrong.
That check is there so that we ignore the cpu_extra stuff if the kernel parameter was passed, given that in that case new_log_buf_len would be set.
> We should be checking for log_buf_len set instead.
When log_buf_len=n is set as a kernel parameter log_buf_len_setup() will set new_log_buf_len to something, the sanity test to not update the ring buffer unless the value passed is greater than the default value is checked by log_buf_len_setup().
>> + new_log_buf_len = __LOG_BUF_LEN + cpu_extra; > > You could also move the whole thing below the return statement, that way > we can avoid double checking new_log_buf_len. Otherwise looks kinda > weird.
If we did we'd be forcing the kernel parameter to be used to enable this functionality, but we don't want that.
Luis
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