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McKenney" , Josh Triplett , "Joel Fernandes (Google)" , Steven Rostedt , Mathieu Desnoyers , Lai Jiangshan , Stephen Rothwell , rcu@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] refperf: work around 64-bit division Message-ID: <20200530035230.GA2019114@ubuntu-s3-xlarge-x86> References: <20200529201600.493808-1-arnd@arndb.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200529201600.493808-1-arnd@arndb.de> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, May 29, 2020 at 10:15:51PM +0200, Arnd Bergmann wrote: > A 64-bit division was introduced in refperf, breaking compilation > on all 32-bit architectures: > > kernel/rcu/refperf.o: in function `main_func': > refperf.c:(.text+0x57c): undefined reference to `__aeabi_uldivmod' > > Work it by using div_u64 to mark the expensive operation. > > Fixes: bd5b16d6c88d ("refperf: Allow decimal nanoseconds") > Signed-off-by: Arnd Bergmann > --- > kernel/rcu/refperf.c | 9 +++++++-- > 1 file changed, 7 insertions(+), 2 deletions(-) > > diff --git a/kernel/rcu/refperf.c b/kernel/rcu/refperf.c > index 47df72c492b3..c2366648981d 100644 > --- a/kernel/rcu/refperf.c > +++ b/kernel/rcu/refperf.c > @@ -386,7 +386,7 @@ static int main_func(void *arg) > if (torture_must_stop()) > goto end; > > - result_avg[exp] = 1000 * process_durations(nreaders) / (nreaders * loops); > + result_avg[exp] = div_u64(1000 * process_durations(nreaders), nreaders * loops); > } > > // Print the average of all experiments > @@ -397,9 +397,14 @@ static int main_func(void *arg) > strcat(buf, "Threads\tTime(ns)\n"); > > for (exp = 0; exp < nruns; exp++) { > + u64 avg; > + u32 rem; > + > if (errexit) > break; > - sprintf(buf1, "%d\t%llu.%03d\n", exp + 1, result_avg[exp] / 1000, (int)(result_avg[exp] % 1000)); > + > + avg = div_s64_rem(result_avg[exp], 1000, &rem); Shouldn't this be div_u64_rem? result_avg is u64. > + sprintf(buf1, "%d\t%llu.%03d\n", exp + 1, avg, rem); Would %03u be the better specifier since rem is u32? > strcat(buf, buf1); > } > > -- > 2.26.2 > Cheers, Nathan