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Message-ID: <20150427203718.GG29351@xo-6d-61-c0.localdomain> Date: Mon, 27 Apr 2015 22:37:18 +0200 From: Pavel Machek <pavel@....cz> To: Pengfei Yuan <0xcoolypf@...il.com> Cc: linux-kernel@...r.kernel.org Subject: Re: Why not build kernel with -O3 Hi! > I have conducted some experiments to compare kernels built with -O2 > and -O3. Here are the results: > > Application Performance O2 Performance O3 Improvement > Apache 127814.14 req/s 130321.24 req/s 1.96% > Nginx 537589.08 req/s 556723.32 req/s 3.56% > MySQL 70661.38 tx/s 71008.47 tx/s 0.49% > PostgreSQL 79763.39 tx/s 79535.59 tx/s -0.29% > Redis 352547.47 op/s 405417.24 op/s 15.0% > Memcached 844439.14 op/s 845321.79 op/s 0.10% > > Geomean: +3.34% > > Experiment environment: Linux 3.19.3, GCC 4.9.3 prerelease, Core-i7 > 4770, 32G RAM, 10GbE > > LMbench microbenchmark also shows reduction in various latencies, as > well as increase of throughputs. What is the size difference with -O3? Do you have mostly-userspace benchmark? (kernel build?) -O3 could hurt there if it produces bigger code.. Pavel -- (english) http://www.livejournal.com/~pavelmachek cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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