Date: Tue, 1 Jan 2008 13:22:49 +0100 From: Gergely CZUCZY <phoemix@harmless.hu> To: Kris Kennaway <kris@FreeBSD.org> Cc: freebsd-performance@freebsd.org, Ivan Voras <ivoras@freebsd.org> Subject: Re: mysql scaling questions Message-ID: <20080101122249.GA81405@harmless.hu> In-Reply-To: <4779BBE8.2050608@FreeBSD.org> References: <20071204130810.GA77186@harmless.hu> <47779AA7.2060801@FreeBSD.org> <20071230132451.GA61295@harmless.hu> <47779EBC.5020900@FreeBSD.org> <20071230134354.GA63555@harmless.hu> <4777A65C.8020406@FreeBSD.org> <20071230141118.GA67574@harmless.hu> <4777AB9C.1010003@FreeBSD.org> <flb6bp$8kq$1@ger.gmane.org> <4779BBE8.2050608@FreeBSD.org>
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--y0ulUmNC+osPPQO6 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Tue, Jan 01, 2008 at 05:04:56AM +0100, Kris Kennaway wrote: > Ivan Voras wrote: > >Kris Kennaway wrote: > >>Gergely CZUCZY wrote: > >>>>It looks like myisam is doing huge numbers of concurrent reads of the > >>>>same file which is running into exclusive locking in the kernel > >>>>(vnode interlock and lockbuilder mtxpool). Does it not do any > >>>>caching of the data in userspace but relies on querying into the > >>>>kernel every time? innodb doesn't have this behaviour. > >>>Sorry, but was this a rethorical kind of question, or was this > >>>addressed to me? :) > >>>If the later, then how do I find this out? > >>It's a general question. It looks like myisam either has a design > >>deficiency in this regard or it has poor defaults. If it can be made to > >>improve caching of the data in userland then performance should improve. > >Isn't this common for software developed for Linux? I mean assuming > >syscalls are cheap; for example: gettimeofday(2), settitle(2), etc. I > >don't think the applications should be blamed for relying on performance > >optimizations not present in FreeBSD. Saying applications must do their > >own caching instead of relying on the kernel and need to avoid > >concurrent accesses to the same file seems like a doctrine from the dark > >ages. >=20 > Why? Even if Linux magically has faster syscalls somehow, they are still= not zero cost so avoiding huge numbers of unnecessary trips=20 > into the kernel is in no sense a "doctrine from the dark ages". Besides,= if my hypothesis about the problem is correct then mysql=20 > itself does this with the alternate innodb backend anyway. There's this SYSCALL CPU extension with the SYSENTER/SYSEXIT features. IIRC Linux takes advantage of this, while FreeBSD doesn't. I might be wrong here, of course. Sincerely, Gergely Czuczy mailto: gergely.czuczy@harmless.hu --=20 Weenies test. Geniuses solve problems that arise. --y0ulUmNC+osPPQO6 Content-Type: application/pgp-signature Content-Disposition: inline -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.4 (FreeBSD) owF9Vs+LHEUUXhMM0uAhePAmj4gkITOT2ZCNuxOya7K7hjHrD7IbYzYI1nS/ni6n uqpTVT2zveJBvCiIiCAIHiJ48aLxoFcPgldP/gn+IX5VPbObQPQ2XVXvve+973vv zVfPn1w6cfqvX369f+GLr7975qfnXh5dKGvv9bhbCjuVurvc7y93V5cv91e6V7or WT66siL48traWn/11bWbh/1vN432rH13r6l4QJ4P/MVKCamvUloI69hfq33eXU0W 77akq4yTXho9IKmV1Hx0t2eFdjnb7rZOTSb1eEAPauM561ZWai9GipPkbU17NXfo DaGpv9yhS/3+KglP/ZVB//Jg5cr1N+lCH7A7dMtKR7dYazETDc0sPA2SdRpOYfmu scIdn63/x9v19Ztsx6wa2ty/s7l/7/Gb9fWhJ2XMxJGSE6aykU6UBD+ZAXYq6jGT rssRW0cmp9TotLYWiZJlkcUzX/DcF0yZcqmYZoVMi+DG1loHR0jdEB+kqnZyygiZ TtrjYE4TtprV3Mu5qTYZBwu24R0JnUWDUS1VxpZKf1AZo873iLYMO5KetPFAjJfN 3Ekq0iIEaPFRJrwIwWqHRCqRMo3qkIKSsDcaFLFtjnAeZ9QCI57imrwseQMvAG+E aOz0WU+FQDq+QKojxm9pattrjXeNtU0nBpqBp/hGIKYvjJWpUIQKZAEggrugpQ4Z e/S09SGyzLJznBFgheiD8+3FsM1LCRSpE35qKsws1GAIBuA3hjO134jvh/5sCD5m zRaRFxFRwafyzxIeLXILRhk7OdbRTca5TCXrtGmZCwTzWNgsIJc+GoAaC5tc1Mq7 ECAPNyn0OoJ/AWa9ic5kWVmD4v0PVUrETJBcxTY3thQa1LnC1CqjuX2s9jByEQGl pizBKF6TM7mfCQufIFCZCmUMxztS1wcbKFTJQCWcq0vED25c40CMQtYwSgsW1dVo wQeirBRmw5h9UIHJM9Gcu3S+Qy4ceMXxg33ao2FwlJk5Hj2JSYmqUuA81Nwt8KMc I4WOaUFBi1GA5olcgy9TIaQ8nBsHpVfQRGhBVOl1y3xjd6tHuyKaPxGorF1sCyCQ Nrqa6aNyS+08WjiU/bHYx90Y205zKz0xNTILHh4bACJNgzQdtR1Dx93vmMu5oCAf k3pMPlxZU84ZtpPgS4zZgb1rl/r4uls0G0TbU3At85YiqGUcGgWTKwgrFwAMUhcc OVMyNB/V30TGoGmlriWxRodsDbSAArg5/KfNM0wnDlmI0N5WVq4Fs5gCi1JAVqi1 NshMu5DUmadnRSGlMxD9DfQM+qYDMMimRAJNZfDKhRkwQltGE+gX6yCO2xTDglPf ir1s3AM1R+IdqzxOm1beM7RmKymFamj0/2IijUQ6YXCGIYj530v20MJ8dm62e293 8/rODm2+cwdqxqZyUMixM1xvv7W3ffti+PHecI9yFr6GzKDn4e3NpOXDiwlgiAzL xyPTtmOl64RxD9rnWlyMxl7oMDkufFA6dk4oPxB1krhHauzVXpLsSqg86K+TJEdr 6rBOD5ukFFJ5E3ouHvfSePwaNnKpQFmvqJOk2w1lususwyD3mGo9uomPOujSGTU9 KnKoAzaswI5E3M82Tj67FFb/4n/D6RMfrS99/4j/+Xv/45d+PtX8+Wj5zKdf/vHi 2nDp4daHP24NPv/hhf3pN6cefvL7Kx/svP/bvw== =jKfX -----END PGP SIGNATURE----- --y0ulUmNC+osPPQO6--
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