linux-kernel - Re: [PATCH v4 3/3] genirq: Adaptive Global Software Interrupt Moderation (GSIM).

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Message-ID: <202601160433.z2rdE9lE-lkp@intel.com>
Date: Fri, 16 Jan 2026 05:14:54 +0800
From: kernel test robot <lkp@...el.com>
To: Luigi Rizzo <lrizzo@...gle.com>, Thomas Gleixner <tglx@...utronix.de>,
	Marc Zyngier <maz@...nel.org>, Luigi Rizzo <rizzo.unipi@...il.com>,
	Paolo Abeni <pabeni@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Sean Christopherson <seanjc@...gle.com>,
	Jacob Pan <jacob.jun.pan@...ux.intel.com>
Cc: oe-kbuild-all@...ts.linux.dev,
	Linux Memory Management List <linux-mm@...ck.org>,
	linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org,
	Bjorn Helgaas <helgaas@...nel.org>,
	Willem de Bruijn <willemb@...gle.com>
Subject: Re: [PATCH v4 3/3] genirq: Adaptive Global Software Interrupt
 Moderation (GSIM).

Hi Luigi,

kernel test robot noticed the following build warnings:

[auto build test WARNING on linus/master]
[also build test WARNING on v6.19-rc5]
[cannot apply to tip/irq/core next-20260115]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Luigi-Rizzo/genirq-Add-flags-for-software-interrupt-moderation/20260116-000808
base:   linus/master
patch link:    https://lore.kernel.org/r/20260115155942.482137-4-lrizzo%40google.com
patch subject: [PATCH v4 3/3] genirq: Adaptive Global Software Interrupt Moderation (GSIM).
config: mips-randconfig-r051-20260116 (https://download.01.org/0day-ci/archive/20260116/202601160433.z2rdE9lE-lkp@intel.com/config)
compiler: clang version 22.0.0git (https://github.com/llvm/llvm-project 9b8addffa70cee5b2acc5454712d9cf78ce45710)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20260116/202601160433.z2rdE9lE-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@...el.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202601160433.z2rdE9lE-lkp@intel.com/

All warnings (new ones prefixed by >>):

>> kernel/irq/irq_moderation.c:432:40: warning: overflow in expression; result is 1'410'065'408 with type 'long' [-Winteger-overflow]
     432 |                 recent = (now - epoch_start_ns) < 10 * NSEC_PER_SEC;
         |                                                   ~~~^~~~~~~~~~~~~~
   1 warning generated.


vim +432 kernel/irq/irq_moderation.c

   410	
   411	/* Print statistics */
   412	static void rd_stats(struct seq_file *p)
   413	{
   414		ulong global_intr_rate = 0, global_irq_high = 0;
   415		ulong local_irq_high = 0, hardirq_high = 0;
   416		uint delay_us = irq_mod_info.delay_us;
   417		u64 now = ktime_get_ns();
   418		int cpu, active_cpus = 0;
   419	
   420		seq_printf(p, HEAD_FMT,
   421			   "# CPU", "irq/s", "loc_irq/s", "cpus", "delay_ns",
   422			   "irq_hi", "loc_irq_hi", "hardirq_hi", "timer_set",
   423			   "enqueue", "stray_irq");
   424	
   425		for_each_possible_cpu(cpu) {
   426			struct irq_mod_state cur, *m = per_cpu_ptr(&irq_mod_state, cpu);
   427			u64 epoch_start_ns;
   428			bool recent;
   429	
   430			/* Accumulate and print only recent samples */
   431			epoch_start_ns = atomic64_read(&m->epoch_start_ns);
 > 432			recent = (now - epoch_start_ns) < 10 * NSEC_PER_SEC;
   433	
   434			/* Copy statistics, will only use some 32bit values, races ok. */
   435			data_race(cur = *per_cpu_ptr(&irq_mod_state, cpu));
   436			if (recent) {
   437				active_cpus++;
   438				global_intr_rate += cur.global_intr_rate;
   439			}
   440	
   441			global_irq_high += cur.global_irq_high;
   442			local_irq_high += cur.local_irq_high;
   443			hardirq_high += cur.hardirq_high;
   444	
   445			seq_printf(p, BODY_FMT,
   446				   cpu,
   447				   recent * cur.global_intr_rate,
   448				   recent * cur.local_intr_rate,
   449				   recent * (cur.scaled_cpu_count + 128) / 256,
   450				   recent * cur.mod_ns,
   451				   cur.global_irq_high,
   452				   cur.local_irq_high,
   453				   cur.hardirq_high,
   454				   cur.timer_set,
   455				   cur.enqueue,
   456				   cur.stray_irq);
   457		}
   458	
   459		seq_printf(p, "\n"
   460			   "enabled              %s\n"
   461			   "delay_us             %u\n"
   462			   "target_intr_rate     %u\n"
   463			   "hardirq_percent      %u\n"
   464			   "update_ms            %u\n"
   465			   "scale_cpus           %u\n",
   466			   str_yes_no(delay_us > 0),
   467			   delay_us,
   468			   irq_mod_info.target_intr_rate, irq_mod_info.hardirq_percent,
   469			   irq_mod_info.update_ms, irq_mod_info.scale_cpus);
   470	
   471		seq_printf(p,
   472			   "intr_rate            %lu\n"
   473			   "irq_high             %lu\n"
   474			   "my_irq_high          %lu\n"
   475			   "hardirq_percent_high %lu\n"
   476			   "total_interrupts     %u\n"
   477			   "total_cpus           %u\n",
   478			   active_cpus ? global_intr_rate / active_cpus : 0,
   479			   global_irq_high, local_irq_high, hardirq_high,
   480			   READ_ONCE(*((u32 *)&irq_mod_info.total_intrs)),
   481			   READ_ONCE(*((u32 *)&irq_mod_info.total_cpus)));
   482	}
   483	

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki