* [PATCH] refperf: work around 64-bit division @ 2020-05-29 20:15 Arnd Bergmann 2020-05-29 21:41 ` Paul E. McKenney ` (2 more replies) 0 siblings, 3 replies; 7+ messages in thread From: Arnd Bergmann @ 2020-05-29 20:15 UTC (permalink / raw) To: Paul E. McKenney, Josh Triplett Cc: Arnd Bergmann, Joel Fernandes (Google), Steven Rostedt, Mathieu Desnoyers, Lai Jiangshan, Stephen Rothwell, rcu, linux-kernel 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 <arnd@arndb.de> --- 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); + sprintf(buf1, "%d\t%llu.%03d\n", exp + 1, avg, rem); strcat(buf, buf1); } -- 2.26.2 ^ permalink raw reply related [flat|nested] 7+ messages in thread
* Re: [PATCH] refperf: work around 64-bit division 2020-05-29 20:15 [PATCH] refperf: work around 64-bit division Arnd Bergmann @ 2020-05-29 21:41 ` Paul E. McKenney 2020-05-29 22:12 ` Randy Dunlap 2020-05-30 3:52 ` Nathan Chancellor 2 siblings, 0 replies; 7+ messages in thread From: Paul E. McKenney @ 2020-05-29 21:41 UTC (permalink / raw) To: Arnd Bergmann Cc: Josh Triplett, Joel Fernandes (Google), Steven Rostedt, Mathieu Desnoyers, Lai Jiangshan, Stephen Rothwell, rcu, linux-kernel 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 <arnd@arndb.de> Many thanks, Arnd! I queued this and reverted my earlier 64-bit-only restriction, pushing the result out on the -rcu tree's "dev" branch. I also added a couple of Reported-by entries. Thanx, Paul > --- > 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); > + sprintf(buf1, "%d\t%llu.%03d\n", exp + 1, avg, rem); > strcat(buf, buf1); > } > > -- > 2.26.2 > ^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH] refperf: work around 64-bit division 2020-05-29 20:15 [PATCH] refperf: work around 64-bit division Arnd Bergmann 2020-05-29 21:41 ` Paul E. McKenney @ 2020-05-29 22:12 ` Randy Dunlap 2020-05-30 3:52 ` Nathan Chancellor 2 siblings, 0 replies; 7+ messages in thread From: Randy Dunlap @ 2020-05-29 22:12 UTC (permalink / raw) To: Arnd Bergmann, Paul E. McKenney, Josh Triplett Cc: Joel Fernandes (Google), Steven Rostedt, Mathieu Desnoyers, Lai Jiangshan, Stephen Rothwell, rcu, linux-kernel On 5/29/20 1:15 PM, 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 <arnd@arndb.de> Acked-by: Randy Dunlap <rdunlap@infradead.org> # build-tested Thanks. > --- > 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); > + sprintf(buf1, "%d\t%llu.%03d\n", exp + 1, avg, rem); > strcat(buf, buf1); > } > > -- ~Randy ^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH] refperf: work around 64-bit division 2020-05-29 20:15 [PATCH] refperf: work around 64-bit division Arnd Bergmann 2020-05-29 21:41 ` Paul E. McKenney 2020-05-29 22:12 ` Randy Dunlap @ 2020-05-30 3:52 ` Nathan Chancellor 2020-05-30 8:01 ` Arnd Bergmann 2 siblings, 1 reply; 7+ messages in thread From: Nathan Chancellor @ 2020-05-30 3:52 UTC (permalink / raw) To: Arnd Bergmann Cc: Paul E. McKenney, Josh Triplett, Joel Fernandes (Google), Steven Rostedt, Mathieu Desnoyers, Lai Jiangshan, Stephen Rothwell, rcu, linux-kernel 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 <arnd@arndb.de> > --- > 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 ^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH] refperf: work around 64-bit division 2020-05-30 3:52 ` Nathan Chancellor @ 2020-05-30 8:01 ` Arnd Bergmann 2020-05-30 12:47 ` Paul E. McKenney 2020-05-31 20:03 ` Paul E. McKenney 0 siblings, 2 replies; 7+ messages in thread From: Arnd Bergmann @ 2020-05-30 8:01 UTC (permalink / raw) To: Nathan Chancellor Cc: Paul E. McKenney, Josh Triplett, Joel Fernandes (Google), Steven Rostedt, Mathieu Desnoyers, Lai Jiangshan, Stephen Rothwell, rcu, linux-kernel On Sat, May 30, 2020 at 5:52 AM Nathan Chancellor <natechancellor@gmail.com> wrote: > On Fri, May 29, 2020 at 10:15:51PM +0200, Arnd Bergmann wrote: > > 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. Yes, you are right. Actually that would be an important optimization since div_u64_rem() optimizes for constant divisors while div_s64_rem uses the slow path. > > + sprintf(buf1, "%d\t%llu.%03d\n", exp + 1, avg, rem); > > Would %03u be the better specifier since rem is u32? Yes, though this makes no difference in practice. Paul, should I send a fixup for these two, or do you prefer to just edit it in place? Arnd ^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH] refperf: work around 64-bit division 2020-05-30 8:01 ` Arnd Bergmann @ 2020-05-30 12:47 ` Paul E. McKenney 2020-05-31 20:03 ` Paul E. McKenney 1 sibling, 0 replies; 7+ messages in thread From: Paul E. McKenney @ 2020-05-30 12:47 UTC (permalink / raw) To: Arnd Bergmann Cc: Nathan Chancellor, Josh Triplett, Joel Fernandes (Google), Steven Rostedt, Mathieu Desnoyers, Lai Jiangshan, Stephen Rothwell, rcu, linux-kernel On Sat, May 30, 2020 at 10:01:36AM +0200, Arnd Bergmann wrote: > On Sat, May 30, 2020 at 5:52 AM Nathan Chancellor > <natechancellor@gmail.com> wrote: > > On Fri, May 29, 2020 at 10:15:51PM +0200, Arnd Bergmann wrote: > > > 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. > > Yes, you are right. Actually that would be an important optimization > since div_u64_rem() optimizes for constant divisors while div_s64_rem > uses the slow path. > > > > + sprintf(buf1, "%d\t%llu.%03d\n", exp + 1, avg, rem); > > > > Would %03u be the better specifier since rem is u32? > > Yes, though this makes no difference in practice. > > Paul, should I send a fixup for these two, or do you prefer to just > edit it in place? I will apply it with Randy's Ack, thank you all! Thanx, Paul ^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH] refperf: work around 64-bit division 2020-05-30 8:01 ` Arnd Bergmann 2020-05-30 12:47 ` Paul E. McKenney @ 2020-05-31 20:03 ` Paul E. McKenney 1 sibling, 0 replies; 7+ messages in thread From: Paul E. McKenney @ 2020-05-31 20:03 UTC (permalink / raw) To: Arnd Bergmann Cc: Nathan Chancellor, Josh Triplett, Joel Fernandes (Google), Steven Rostedt, Mathieu Desnoyers, Lai Jiangshan, Stephen Rothwell, rcu, linux-kernel On Sat, May 30, 2020 at 10:01:36AM +0200, Arnd Bergmann wrote: > On Sat, May 30, 2020 at 5:52 AM Nathan Chancellor > <natechancellor@gmail.com> wrote: > > On Fri, May 29, 2020 at 10:15:51PM +0200, Arnd Bergmann wrote: > > > 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. > > Yes, you are right. Actually that would be an important optimization > since div_u64_rem() optimizes for constant divisors while div_s64_rem > uses the slow path. > > > > + sprintf(buf1, "%d\t%llu.%03d\n", exp + 1, avg, rem); > > > > Would %03u be the better specifier since rem is u32? > > Yes, though this makes no difference in practice. > > Paul, should I send a fixup for these two, or do you prefer to just > edit it in place? And here is the update, thank you all! Thanx, Paul ------------------------------------------------------------------------ commit 0dd4132157c2cf6bec2a0a6e04163067323abdb1 Author: Arnd Bergmann <arnd@arndb.de> Date: Fri May 29 14:36:26 2020 -0700 refperf: Work around 64-bit division 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' Fix this by using div_u64 to mark the expensive operation. [ paulmck: Update primitive and format per Nathan Chancellor. ] Fixes: bd5b16d6c88d ("refperf: Allow decimal nanoseconds") Reported-by: kbuild test robot <lkp@intel.com> Reported-by: Valdis Klētnieks <valdis.kletnieks@vt.edu> Acked-by: Randy Dunlap <rdunlap@infradead.org> # build-tested Signed-off-by: Arnd Bergmann <arnd@arndb.de> Signed-off-by: Paul E. McKenney <paulmck@kernel.org> diff --git a/kernel/rcu/refperf.c b/kernel/rcu/refperf.c index 99434e7..3b72925 100644 --- a/kernel/rcu/refperf.c +++ b/kernel/rcu/refperf.c @@ -478,7 +478,7 @@ 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 @@ -489,9 +489,13 @@ static int main_func(void *arg) strcat(buf, "Runs\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_u64_rem(result_avg[exp], 1000, &rem); + sprintf(buf1, "%d\t%llu.%03u\n", exp + 1, avg, rem); strcat(buf, buf1); } ^ permalink raw reply related [flat|nested] 7+ messages in thread
end of thread, other threads:[~2020-05-31 20:03 UTC | newest] Thread overview: 7+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- 2020-05-29 20:15 [PATCH] refperf: work around 64-bit division Arnd Bergmann 2020-05-29 21:41 ` Paul E. McKenney 2020-05-29 22:12 ` Randy Dunlap 2020-05-30 3:52 ` Nathan Chancellor 2020-05-30 8:01 ` Arnd Bergmann 2020-05-30 12:47 ` Paul E. McKenney 2020-05-31 20:03 ` Paul E. McKenney
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