Date: Tue, 16 May 2006 18:00:41 +0300 (EEST) From: Dmitry Pryanishnikov <dmitry@atlantis.dp.ua> To: "Matthew D. Fuller" <fullermd@over-yonder.net> Cc: freebsd-stable@freebsd.org, Kris Kennaway <kris@obsecurity.org> Subject: Re: INVARIANTS (was Re: RELENG_4 -> 5 -> 6: significant performance regression) Message-ID: <20060516175026.I94440@atlantis.atlantis.dp.ua> In-Reply-To: <20060513160337.GG3874@over-yonder.net> References: <20060427160536.M96305@atlantis.atlantis.dp.ua> <20060427181226.GA66431@xor.obsecurity.org> <20060428122448.K57436@atlantis.atlantis.dp.ua> <20060428182818.GA10410@xor.obsecurity.org> <20060512161836.R75964@atlantis.atlantis.dp.ua> <20060513020051.GB18438@xor.obsecurity.org> <20060513084236.W74146@atlantis.atlantis.dp.ua> <20060513143740.GA46313@xor.obsecurity.org> <20060513155232.GF3874@over-yonder.net> <20060513155826.GA47324@xor.obsecurity.org> <20060513160337.GG3874@over-yonder.net>
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Hello! On Sat, 13 May 2006, Matthew D. Fuller wrote: > On Sat, May 13, 2006 at 11:58:26AM -0400 I heard the voice of > Kris Kennaway, and lo! it spake thus: >> >> FYI, INVARIANTS adds checks but does not (is not supposed to) divert >> code paths. > > It does at least in UMA; it does a lot of bzero()/NULL'ing out of > memory, which might hide later uninitialized-use bugs that could bite > you without it (and, of course, probably burns a fair chunk of CPU to > do it ;). I know I've heard other cases over the past 5 years or so; > that's the only one I've heard recently or can check, but I wouldn't > be too surprised if there were others. This is exactly the point of my suggestion: use separate option (e.g., INVARIANTS_EXTENDED) for this additional bzero()/NULL'ing and other performance-expensive checks, and leave only simple asserts under basic INVARIANTS options. IMHO this will encourage (or, at least, not discourage) use of INVARIANTS-enabled kernels in production conditions which for sure will help to analyze latent, heavy load-specific, bugs. > Matthew Fuller (MF4839) | fullermd@over-yonder.net > Systems/Network Administrator | http://www.over-yonder.net/~fullermd/ > On the Internet, nobody can hear you scream. Sincerely, Dmitry -- Atlantis ISP, System Administrator e-mail: dmitry@atlantis.dp.ua nic-hdl: LYNX-RIPE
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