From: Peter Zijlstra <peterz@infradead.org>
To: Nadav Amit <namit@vmware.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
Ingo Molnar <mingo@kernel.org>, Borislav Petkov <bp@alien8.de>,
"tglx@linutronix.de" <tglx@linutronix.de>,
"luto@kernel.org" <luto@kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 0/5] x86/percpu semantics and fixes
Date: Fri, 8 Mar 2019 21:56:37 +0100 [thread overview]
Message-ID: <20190308205637.GC2482@worktop.programming.kicks-ass.net> (raw)
In-Reply-To: <64526663-1F10-42A6-A005-92657264D587@vmware.com>
On Fri, Mar 08, 2019 at 07:35:17PM +0000, Nadav Amit wrote:
> Nice script! I keep asking myself how comparing two binaries can provide
> some “number” to indicate how “good” the binary is (at least relatively to
> another one) - either during compilation or after. Code size, as you show,
> is the wrong metric.
Right; I'm still pondering other metrics, like:
readelf -WS | grep AX | grep -v -e init -e exit -e altinstr -e unlikely -e fixup
which is only 'fast' path text.
> Anyhow, I am a little disappointed (and surprised) that in most cases that I
> played with, this kind of optimizations have marginal impact on performance
> at best, even when the binary changes “a lot” and when microbenchmarks are
> used.
Right, but if we don't care, it'll be death by 1000 cuts.
Anyway, can anybody explain percpu_stable_op() vs percpu_from_op() ?
I'm thinking of a variant of Linus' patch, but I'm confused about the
above.
next prev parent reply other threads:[~2019-03-08 20:56 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-02-27 10:12 [PATCH 0/5] x86/percpu semantics and fixes Peter Zijlstra
2019-02-27 10:12 ` [PATCH 1/5] x86/percpu: Differentiate this_cpu_{}() and __this_cpu_{}() Peter Zijlstra
2019-02-27 16:14 ` Linus Torvalds
2019-02-27 16:48 ` Peter Zijlstra
2019-02-27 17:17 ` Linus Torvalds
2019-02-27 17:34 ` Peter Zijlstra
2019-02-27 17:38 ` Linus Torvalds
2019-02-27 17:57 ` Nadav Amit
2019-02-27 18:55 ` Nadav Amit
2019-02-27 19:41 ` Linus Torvalds
2019-03-08 13:35 ` Peter Zijlstra
2019-02-27 10:12 ` [PATCH 2/5] x86/percpu: Relax smp_processor_id() Peter Zijlstra
2019-02-27 10:12 ` [PATCH 3/5] x86/percpu, x86/irq: Relax {set,get}_irq_regs() Peter Zijlstra
2019-02-27 10:12 ` [PATCH 4/5] x86/percpu, x86/tlb: Relax cpu_tlbstate accesses Peter Zijlstra
2019-02-27 10:12 ` [PATCH 5/5] x86/percpu, sched/fair: Avoid local_clock() Peter Zijlstra
2019-02-27 10:24 ` [PATCH 6/5] x86/percpu: Optimize raw_cpu_xchg() Peter Zijlstra
2019-02-27 14:43 ` Peter Zijlstra
2019-02-27 23:16 ` [PATCH 0/5] x86/percpu semantics and fixes Nadav Amit
2019-03-08 14:50 ` Peter Zijlstra
2019-03-08 19:35 ` Nadav Amit
2019-03-08 20:56 ` Peter Zijlstra [this message]
2019-03-10 12:46 ` Peter Zijlstra
2019-03-08 22:48 ` Peter Zijlstra
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