From: David Miller <davem@davemloft.net>
To: vijay.ac.kumar@oracle.com
Cc: sparclinux@vger.kernel.org, rob.gardner@oracle.com,
anthony.yznaga@oracle.com, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 0/2] sparc64: Use low latency path to resume idle cpu
Date: Thu, 20 Jul 2017 12:57:10 -0700 (PDT) [thread overview]
Message-ID: <20170720.125710.1645099626446989744.davem@davemloft.net> (raw)
In-Reply-To: <1499545424-415240-1-git-send-email-vijay.ac.kumar@oracle.com>
From: Vijay Kumar <vijay.ac.kumar@oracle.com>
Date: Sat, 8 Jul 2017 14:23:42 -0600
> cpu_poke is a low latency path to resume the target cpu if suspended
> using cpu_yield. Use cpu poke to resume cpu if supported by hypervisor.
>
> hackbench results (lower is better):
> Number of
> Process: w/o fix with fix
> 1 0.012 0.010
> 10 0.021 0.019
> 100 0.151 0.148
So this only works for a cpu which has yielded.
The kernel sends reschedule events to both idle and non-idle cpus.
That's why you have to have that fallback code to still send the
mondo IPI right?
For the case where POKE works, it seems like completely unnecessary
overhead to set the PIL interrupt. Just disable local cpu interrupts
and call schedule_ipi() directly.
I bet that improves your benchmark even more.
next prev parent reply other threads:[~2017-07-20 19:57 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-07-08 20:23 [PATCH 0/2] sparc64: Use low latency path to resume idle cpu Vijay Kumar
2017-07-08 20:23 ` [PATCH 1/2] sparc64: Add a new hypercall CPU_POKE Vijay Kumar
2017-07-08 20:23 ` [PATCH 2/2] sparc64: Use cpu_poke to resume idle cpu Vijay Kumar
2017-07-20 19:58 ` David Miller
2017-07-21 2:47 ` Vijay Kumar
2017-07-20 19:57 ` David Miller [this message]
2017-07-21 2:44 ` [PATCH 0/2] sparc64: Use low latency path " Vijay Kumar
2017-07-21 2:55 ` David Miller
2017-07-21 3:36 ` Vijay Kumar
2017-07-21 3:45 ` David Miller
2017-07-21 4:11 ` Vijay Kumar
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