Date: Fri, 19 Aug 2011 13:50:43 +0400 From: Slawa Olhovchenkov <slw@zxy.spb.ru> To: "Robert N. M. Watson" <rwatson@FreeBSD.org> Cc: Lev Serebryakov <lev@FreeBSD.org>, freebsd-arch@freebsd.org Subject: Re: FreeBSD problems and preliminary ways to solve Message-ID: <20110819095043.GB2362@zxy.spb.ru> In-Reply-To: <FBF0BBA4-7694-438C-93CF-84E25ABAFF73@FreeBSD.org> References: <slrnj4oiiq.21rg.vadim_nuclight@kernblitz.nuclight.avtf.net> <810527321.20110819123700@serebryakov.spb.ru> <alpine.BSF.2.00.1108190939340.93669@fledge.watson.org> <319607032.20110819125005@serebryakov.spb.ru> <alpine.BSF.2.00.1108190954420.93669@fledge.watson.org> <20110819090536.GA92576@zxy.spb.ru> <FBF0BBA4-7694-438C-93CF-84E25ABAFF73@FreeBSD.org>
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On Fri, Aug 19, 2011 at 10:36:29AM +0100, Robert N. M. Watson wrote: > > On 19 Aug 2011, at 10:05, Slawa Olhovchenkov wrote: > > >> Is the issue here that FreeBSD is dropping more packes, or just that FreeBSD > >> is reporting that it drops packets? Historically, we've returned ENOBUFS from > >> datagram sockets when the interface queue is overflowed, but some other > >> systems (most noticeably Linux) simply return success when they drop a packet > >> on an outgoing interface queue. You can debate which is the better model, but > >> one impact is that sometimes people report errors on FreeBSD that they don't > >> see on Linux -- when actually, the same failure is present, we just allow the > >> application to learn about it. > > > > Historically, Linux on datagram (UDP) socket allow use select, FreeBSD > > -- don't allow. FreeBSD always report 'UDP socket ready to transmit'. > > And after try to send packet -- 'oops, ENOBUFS'. > > > And if you have two consumers sending UDP on Linux, they both get unreported 50% packet loss, to my understanding? In my test I use netperf. netperf/UDP on linux send only packets can be proccessed by box (and NIC) and packets don't drop. netperf don't allocate all CPU cycles. netperf/UDP on FreeBSD get all CPU, try to send HUGE UDP flow and report about massive packets drop. select on UDP socket report 'ready' allways.
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