From: Peter Zijlstra <peterz@infradead.org>
To: Marcelo Tosatti <mtosatti@redhat.com>
Cc: Frederic Weisbecker <frederic@kernel.org>,
Yair Podemsky <ypodemsk@redhat.com>,
linux@armlinux.org.uk, mpe@ellerman.id.au, npiggin@gmail.com,
christophe.leroy@csgroup.eu, hca@linux.ibm.com,
gor@linux.ibm.com, agordeev@linux.ibm.com,
borntraeger@linux.ibm.com, svens@linux.ibm.com,
davem@davemloft.net, tglx@linutronix.de, mingo@redhat.com,
bp@alien8.de, dave.hansen@linux.intel.com, x86@kernel.org,
hpa@zytor.com, will@kernel.org, aneesh.kumar@linux.ibm.com,
akpm@linux-foundation.org, arnd@arndb.de, keescook@chromium.org,
paulmck@kernel.org, jpoimboe@kernel.org, samitolvanen@google.com,
ardb@kernel.org, juerg.haefliger@canonical.com,
rmk+kernel@armlinux.org.uk, geert+renesas@glider.be,
tony@atomide.com, linus.walleij@linaro.org,
sebastian.reichel@collabora.com, nick.hawkins@hpe.com,
linux-kernel@vger.kernel.org,
linux-arm-kernel@lists.infradead.org,
linuxppc-dev@lists.ozlabs.org, linux-s390@vger.kernel.org,
sparclinux@vger.kernel.org, linux-arch@vger.kernel.org,
linux-mm@kvack.org, vschneid@redhat.com, dhildenb@redhat.com,
alougovs@redhat.com
Subject: Re: [PATCH 3/3] mm/mmu_gather: send tlb_remove_table_smp_sync IPI only to CPUs in kernel mode
Date: Wed, 5 Apr 2023 21:54:57 +0200 [thread overview]
Message-ID: <20230405195457.GC365912@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <ZC3PUkI7N2uEKy6v@tpad>
On Wed, Apr 05, 2023 at 04:43:14PM -0300, Marcelo Tosatti wrote:
> Two points:
>
> 1) For a virtualized system, the overhead is not only of executing the
> IPI but:
>
> VM-exit
> run VM-exit code in host
> handle IPI
> run VM-entry code in host
> VM-entry
I thought we could do IPIs without VMexit these days? Also virt... /me
walks away.
> 2) Depends on the application and the definition of "occasional".
>
> For certain types of applications (for example PLC software or
> RAN processing), upon occurrence of an event, it is necessary to
> complete a certain task in a maximum amount of time (deadline).
If the application is properly NOHZ_FULL and never does a kernel entry,
it will never get that IPI. If it is a pile of shit and does kernel
entries while it pretends to be NOHZ_FULL it gets to keep the pieces and
no amount of crying will get me to care.
next prev parent reply other threads:[~2023-04-05 19:56 UTC|newest]
Thread overview: 37+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-04-04 13:42 [PATCH 0/3] send tlb_remove_table_smp_sync IPI only to necessary CPUs Yair Podemsky
2023-04-04 13:42 ` [PATCH 1/3] arch: Introduce ARCH_HAS_CPUMASK_BITS Yair Podemsky
2023-04-04 13:47 ` David Hildenbrand
2023-04-04 13:42 ` [PATCH 2/3] mm/mmu_gather: send tlb_remove_table_smp_sync IPI only to MM CPUs Yair Podemsky
2023-04-04 14:57 ` Peter Zijlstra
2023-04-04 13:42 ` [PATCH 3/3] mm/mmu_gather: send tlb_remove_table_smp_sync IPI only to CPUs in kernel mode Yair Podemsky
2023-04-04 14:03 ` David Hildenbrand
2023-04-04 15:12 ` Peter Zijlstra
2023-04-04 16:00 ` Peter Zijlstra
2023-04-05 0:53 ` Hillf Danton
2023-04-05 10:43 ` Frederic Weisbecker
2023-04-05 11:10 ` Frederic Weisbecker
2023-04-05 11:41 ` Peter Zijlstra
2023-04-05 12:00 ` David Hildenbrand
2023-04-05 12:05 ` Frederic Weisbecker
2023-04-05 12:31 ` Frederic Weisbecker
2023-04-05 12:45 ` Valentin Schneider
2023-04-06 13:38 ` Peter Zijlstra
2023-04-06 14:11 ` Valentin Schneider
2023-04-06 14:39 ` Peter Zijlstra
2023-04-05 19:45 ` Marcelo Tosatti
2023-04-05 19:52 ` Peter Zijlstra
2023-04-06 12:38 ` Marcelo Tosatti
2023-04-06 13:29 ` Peter Zijlstra
2023-04-06 14:04 ` Peter Zijlstra
2023-04-06 14:42 ` David Hildenbrand
2023-04-06 15:06 ` Peter Zijlstra
2023-04-06 15:02 ` Peter Zijlstra
2023-04-06 15:51 ` David Hildenbrand
2023-04-06 18:27 ` Peter Zijlstra
2023-04-19 11:30 ` David Hildenbrand
2023-04-19 11:39 ` Marcelo Tosatti
2023-04-05 19:43 ` Marcelo Tosatti
2023-04-05 19:54 ` Peter Zijlstra [this message]
2023-04-06 12:49 ` Marcelo Tosatti
2023-04-06 13:32 ` Peter Zijlstra
2023-04-19 11:01 ` Marcelo Tosatti
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