Date: Fri, 8 Mar 2013 20:57:45 +0200 From: Konstantin Belousov <kostikbel@gmail.com> To: Andre Oppermann <andre@freebsd.org> Cc: alc@freebsd.org, freebsd-current@freebsd.org, Alan Cox <alc@rice.edu> Subject: Re: Cleanup and untangling of kernel VM initialization Message-ID: <20130308185745.GV3794@kib.kiev.ua> In-Reply-To: <5139E07E.4040704@freebsd.org> References: <510BC24D.2090406@freebsd.org> <510BF6E0.8070007@rice.edu> <5138C877.9060808@freebsd.org> <20130308091634.GM3794@kib.kiev.ua> <5139E07E.4040704@freebsd.org>
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--E/fydkOSwztHu2te Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Fri, Mar 08, 2013 at 01:58:38PM +0100, Andre Oppermann wrote: > On 08.03.2013 10:16, Konstantin Belousov wrote: > > On Thu, Mar 07, 2013 at 06:03:51PM +0100, Andre Oppermann wrote: > >> pager_map: is used for pager IO to a storage media (disk). Not > >> pageable. Calculation: MAXPHYS * min(max(nbuf/4, 16), 256). > > > > It is more versatile. The space is used for pbufs, and pbufs currently > > also serve for physio, for the clustering, for aio needs. >=20 > Good to know. Isn't the ceiling of MAXPHYS * 256 a bit tight then? I doubt it. The ceiling on the amount of pbufs only limit the concurrency from the subsystems I enumerated. The pbuf allocations are sleepable (usually), so there is no correctness problem from having it sizes slightly lower then could be, and 256 parallel i/o's is good enough still. It might make sense to increase the pbuf KVA for arches with ample KVA, but it would only benefit special workloads which create lot of the concurrent i/o from the specific subsystems. E.g., the clustering cannot create more then 16MB of clusters for write, and with the default MAXPHYS of 128KB, this takes 64 pbufs. --E/fydkOSwztHu2te Content-Type: application/pgp-signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.19 (FreeBSD) iQIcBAEBAgAGBQJROjSpAAoJEJDCuSvBvK1BH7AP/3AkItM7Vjp41hoN8RZqSbr6 +r6P7IF0OFdCypPx6XQs/15lPOXiRQNRcuxdXfo9oQwxO0SrzIIzSP30DVKxx6ex jibatgv+LHMQlkACnQOyktKk9DVNgWzR7KT9sKg6fUtSTHZZCMLvz2z28quUGu/Q T+gTx4CWzNQk81JkuInRWMcJXEzVLjcgHp3JkGIXocwKVq2XX/LT14/28PwpVmy6 uMQQHpW/qK2IY/VpDFVflQTM+onVLO7CUJYNAesXXo1j18mKtab/ATXa9M9oxl6Q 4U4xu0wYEFBaBRSKGVoFn0MNwBaB1pOMrvaPO/lLVkug76WsXBlx0Bji7qX74E5l EMrSq+CVV3NUMPcQQDJIpEJ6ndZb9oRu4fq1jcGpFPFc1qzO8mf8XcrIusKvpSfe WZrF9wnrbsEwutYYQspdgJXxFKfuhRWWKMCHUq8wrFVEhp/b/oh+qCW/v0snsMmG /iHpK/ZM2pzfX3x+5ncnhRc5FPoAolvZ1gujlxoIik5glAkkT9VE1kkl2VwjXpiD E5z+Ti9ckOia7ooMwinjNGDy51UWGAz95bdFAUf+0BGJb3dLJQXO6l9OP2K2OGz9 rGb0tdPwJtx5Wz2Nk/QHURF1bcnqx2KHFe8Tn+BTs6wH3URv84xSK/gXZEesWJ8B oexvUUWf5NDNcMy9lM/k =0QHV -----END PGP SIGNATURE----- --E/fydkOSwztHu2te--
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