From: Marcelo Tosatti <mtosatti@redhat.com>
To: Michal Hocko <mhocko@suse.com>
Cc: Christoph Lameter <cl@linux.com>,
Aaron Tomlin <atomlin@atomlin.com>,
Frederic Weisbecker <frederic@kernel.org>,
Andrew Morton <akpm@linux-foundation.org>,
linux-kernel@vger.kernel.org, linux-mm@kvack.org,
Russell King <linux@armlinux.org.uk>,
Huacai Chen <chenhuacai@kernel.org>,
Heiko Carstens <hca@linux.ibm.com>,
x86@kernel.org, Vlastimil Babka <vbabka@suse.cz>
Subject: Re: [PATCH v5 00/12] fold per-CPU vmstats remotely
Date: Tue, 14 Mar 2023 10:00:46 -0300 [thread overview]
Message-ID: <ZBBv/l6NshXFI8vW@tpad> (raw)
In-Reply-To: <ZBBvuYkWgtVXCV7J@tpad>
On Tue, Mar 14, 2023 at 09:59:37AM -0300, Marcelo Tosatti wrote:
> > Why is that a problem? Out-of-sync stats shouldn't cause major problems.
> > Or can they?
>
> Consider SCHED_FIFO task that is polling the network queue (say
> testpmd).
>
> do {
> if (net_registers->state & DATA_AVAILABLE) {
> process_data)();
> }
> } while (!stopped);
>
> Since this task runs at SCHED_FIFO priority, kworker won't
> be scheduled to run (therefore per-CPU vmstats won't be
> flushed to global vmstats).
>
> Or, if testpmd runs at SCHED_OTHER, then the work item to
> flush per-CPU vmstats causes
>
> testpmd -> kworker
> kworker: flush per-CPU vmstats
> kworker -> testpmd
>
> And this might cause undesired latencies to the packets being
> processed by the testpmd task.
This problem is unrelated to the kswapd problem, but both are addressed
by the patchset.
next prev parent reply other threads:[~2023-03-14 13:01 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-03-13 16:25 Marcelo Tosatti
2023-03-13 16:25 ` [PATCH v5 01/12] this_cpu_cmpxchg: ARM64: switch this_cpu_cmpxchg to locked, add _local function Marcelo Tosatti
2023-03-13 16:25 ` [PATCH v5 02/12] this_cpu_cmpxchg: loongarch: " Marcelo Tosatti
2023-03-13 16:25 ` [PATCH v5 03/12] this_cpu_cmpxchg: S390: " Marcelo Tosatti
2023-03-13 16:25 ` [PATCH v5 04/12] this_cpu_cmpxchg: x86: " Marcelo Tosatti
2023-03-13 16:25 ` [PATCH v5 05/12] add this_cpu_cmpxchg_local and asm-generic definitions Marcelo Tosatti
2023-03-13 16:25 ` [PATCH v5 06/12] convert this_cpu_cmpxchg users to this_cpu_cmpxchg_local Marcelo Tosatti
2023-03-13 16:25 ` [PATCH v5 07/12] mm/vmstat: switch counter modification to cmpxchg Marcelo Tosatti
2023-03-13 16:25 ` [PATCH v5 08/12] vmstat: switch per-cpu vmstat counters to 32-bits Marcelo Tosatti
2023-03-13 16:25 ` [PATCH v5 09/12] mm/vmstat: use xchg in cpu_vm_stats_fold Marcelo Tosatti
2023-03-13 16:25 ` [PATCH v5 10/12] mm/vmstat: switch vmstat shepherd to flush per-CPU counters remotely Marcelo Tosatti
2023-03-13 16:25 ` [PATCH v5 11/12] mm/vmstat: refresh stats remotely instead of via work item Marcelo Tosatti
2023-03-13 16:25 ` [PATCH v5 12/12] vmstat: add pcp remote node draining via cpu_vm_stats_fold Marcelo Tosatti
2023-03-14 12:25 ` [PATCH v5 00/12] fold per-CPU vmstats remotely Michal Hocko
2023-03-14 12:59 ` Marcelo Tosatti
2023-03-14 13:00 ` Marcelo Tosatti [this message]
2023-03-14 14:31 ` Michal Hocko
2023-03-14 18:49 ` Marcelo Tosatti
2023-03-14 21:01 ` Michal Hocko
2023-03-15 0:29 ` Marcelo Tosatti
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