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Date: Tue, 26 May 2020 12:14:08 -0700
From: "Paul E. McKenney" <paulmck@...nel.org>
To: Ingo Molnar <mingo@...nel.org>
Cc: linux-kernel@...r.kernel.org, linux-tip-commits@...r.kernel.org,
"Joel Fernandes (Google)" <joel@...lfernandes.org>,
x86 <x86@...nel.org>
Subject: Re: [PATCH] rcu/performance: Fix kfree_perf_init() build warning on
32-bit kernels
On Tue, May 26, 2020 at 08:27:44PM +0200, Ingo Molnar wrote:
>
> * tip-bot2 for Joel Fernandes (Google) <tip-bot2@...utronix.de> wrote:
>
> > The following commit has been merged into the core/rcu branch of tip:
> >
> > Commit-ID: f87dc808009ac86c790031627698ef1a34c31e25
> > Gitweb: https://git.kernel.org/tip/f87dc808009ac86c790031627698ef1a34c31e25
> > Author: Joel Fernandes (Google) <joel@...lfernandes.org>
> > AuthorDate: Mon, 16 Mar 2020 12:32:26 -04:00
> > Committer: Paul E. McKenney <paulmck@...nel.org>
> > CommitterDate: Mon, 27 Apr 2020 11:02:50 -07:00
> >
> > rcuperf: Add ability to increase object allocation size
> >
> > This allows us to increase memory pressure dynamically using a new
> > rcuperf boot command line parameter called 'rcumult'.
> >
> > Signed-off-by: Joel Fernandes (Google) <joel@...lfernandes.org>
> > Signed-off-by: Paul E. McKenney <paulmck@...nel.org>
> > ---
> > kernel/rcu/rcuperf.c | 5 ++++-
> > 1 file changed, 4 insertions(+), 1 deletion(-)
> >
> > diff --git a/kernel/rcu/rcuperf.c b/kernel/rcu/rcuperf.c
> > index a4a8d09..16dd1e6 100644
> > --- a/kernel/rcu/rcuperf.c
> > +++ b/kernel/rcu/rcuperf.c
> > @@ -88,6 +88,7 @@ torture_param(bool, shutdown, RCUPERF_SHUTDOWN,
> > torture_param(int, verbose, 1, "Enable verbose debugging printk()s");
> > torture_param(int, writer_holdoff, 0, "Holdoff (us) between GPs, zero to disable");
> > torture_param(int, kfree_rcu_test, 0, "Do we run a kfree_rcu() perf test?");
> > +torture_param(int, kfree_mult, 1, "Multiple of kfree_obj size to allocate.");
> >
> > static char *perf_type = "rcu";
> > module_param(perf_type, charp, 0444);
> > @@ -635,7 +636,7 @@ kfree_perf_thread(void *arg)
> > }
> >
> > for (i = 0; i < kfree_alloc_num; i++) {
> > - alloc_ptr = kmalloc(sizeof(struct kfree_obj), GFP_KERNEL);
> > + alloc_ptr = kmalloc(kfree_mult * sizeof(struct kfree_obj), GFP_KERNEL);
> > if (!alloc_ptr)
> > return -ENOMEM;
> >
> > @@ -722,6 +723,8 @@ kfree_perf_init(void)
> > schedule_timeout_uninterruptible(1);
> > }
> >
> > + pr_alert("kfree object size=%lu\n", kfree_mult * sizeof(struct kfree_obj));
>
> There's a new build warning on certain 32-bit kernel builds due to
> this commit:
>
> In file included from ./include/linux/printk.h:7,
> from ./include/linux/kernel.h:15,
> from kernel/rcu/rcuperf.c:13:
> kernel/rcu/rcuperf.c: In function ‘kfree_perf_init’:
> ./include/linux/kern_levels.h:5:18: warning: format ‘%lu’ expects argument of type ‘long unsigned int’, but argument 2 has type ‘unsigned int’ [-Wformat=]
> 5 | #define KERN_SOH "\001" /* ASCII Start Of Header */
> | ^~~~~~
> ./include/linux/kern_levels.h:9:20: note: in expansion of macro ‘KERN_SOH’
> 9 | #define KERN_ALERT KERN_SOH "1" /* action must be taken immediately */
> | ^~~~~~~~
> ./include/linux/printk.h:295:9: note: in expansion of macro ‘KERN_ALERT’
> 295 | printk(KERN_ALERT pr_fmt(fmt), ##__VA_ARGS__)
> | ^~~~~~~~~~
> kernel/rcu/rcuperf.c:726:2: note: in expansion of macro ‘pr_alert’
> 726 | pr_alert("kfree object size=%lu\n", kfree_mult * sizeof(struct kfree_obj));
> | ^~~~~~~~
> kernel/rcu/rcuperf.c:726:32: note: format string is defined here
> 726 | pr_alert("kfree object size=%lu\n", kfree_mult * sizeof(struct kfree_obj));
> | ~~^
> | |
> | long unsigned int
> | %u
>
>
> The reason for the warning is that both kfree_mult and sizeof() are
> 'int' types on 32-bit kernels, while the format string expects a long.
>
> Instead of casting the type to long or tweaking the format string, the
> most straightforward solution is to upgrade kfree_mult to a long.
> Since this depends on CONFIG_RCU_PERF_TEST
Makes sense, and I have queued the patch below, which I am assuming
that you want in the upcoming merge window. If you don't tell me
otherwise, I will send you an urgent pull request later today.
Or, if you just put it directly into -tip yourself:
Reviewed-by: Paul E. McKenney <paulmck@...nel.org>
Either way, please let me know.
> BTW., could we please also rename this code from 'PERF_TEST'/'perf test'
> to 'PERFORMANCE_TEST'/'performance test'? At first glance I always
> mistakenly believe that it's somehow related to perf, while it isn't. =B-)
Fair enough, especially given that perf was there first and is also way
more heavily used. ;-)
But I am guessing that this one is OK for the v5.9 merge window.
Either way, I will update as you say.
Thanx, Paul
------------------------------------------------------------------------
commit 2fbc7d67a2ed108e3ac63296670fecb3a42fddd0
Author: Ingo Molnar <mingo@...nel.org>
Date: Tue May 26 12:10:01 2020 -0700
rcuperf: Fix kfree_mult to match printk() format
This commit changes the type of kfree_mult from int to long in order
to match the printk() format on 32-bit systems.
Reported-by: kbuild test robot <lkp@...el.com>
Signed-off-by: Ingo Molnar <mingo@...nel.org>
Signed-off-by: Paul E. McKenney <paulmck@...nel.org>
diff --git a/kernel/rcu/rcuperf.c b/kernel/rcu/rcuperf.c
index d906ca9..fb3a1f0 100644
--- a/kernel/rcu/rcuperf.c
+++ b/kernel/rcu/rcuperf.c
@@ -93,7 +93,7 @@ torture_param(bool, shutdown, RCUPERF_SHUTDOWN,
torture_param(int, verbose, 1, "Enable verbose debugging printk()s");
torture_param(int, writer_holdoff, 0, "Holdoff (us) between GPs, zero to disable");
torture_param(int, kfree_rcu_test, 0, "Do we run a kfree_rcu() perf test?");
-torture_param(int, kfree_mult, 1, "Multiple of kfree_obj size to allocate.");
+torture_param(long, kfree_mult, 1, "Multiple of kfree_obj size to allocate.");
static char *perf_type = "rcu";
module_param(perf_type, charp, 0444);
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