Date: Tue, 4 Sep 2012 07:04:50 +1000 From: Peter Jeremy <peter@rulingia.com> To: Ragnar Lonn <ragnar@gatorhole.com> Cc: freebsd-hardware@freebsd.org Subject: Re: Load testing knocks out network Message-ID: <20120903210450.GC2654@aspire.rulingia.com> In-Reply-To: <50446681.2080307@gatorhole.com> References: <CAHMRaQfLGY%2BYeDkG7K1GJQ-pmAi6rgT6-gthKQ3j7rSyzr7qVA@mail.gmail.com> <CAHMRaQdv0Wd3u79cxcNBa=aC%2Bv3L3XMEirDtxQ7aKFF0JxxSag@mail.gmail.com> <CAHMRaQfNEPcd6gYhZa0z3D=aEx3ykVpdhpJ9jszVyvaatYjeVw@mail.gmail.com> <50446681.2080307@gatorhole.com>
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--Qbvjkv9qwOGw/5Fx Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On 2012-Sep-03 10:12:49 +0200, Ragnar Lonn <ragnar@gatorhole.com> wrote: >transmit/receive buffers. In newer *Linux* kernels, this memory is being= =20 >allocated in an adaptive manner - i.e. the kernel only allocates a small= =20 >amount of memory to each TCP buffer, and then increases it as necessary=20 >(per connection, depending on transfer speed and network delay to the=20 >other peer). FreeBSD does this as well, though I don't recall when this was added. >I think I actually discussed this with FreeBSD developers a while ago=20 >(on this list even?), and they told me the FreeBSD kernel can only=20 >allocate max 2GB of kernel memory. This is only true on 32-bit kernels. FreeBSD uses a single address space so both kernel and userland need to fit into 4GB on 32-bit systems. On 64-bit systems, KVM is less constrained (it's ~550GB on my amd64). You can check sysctl's vm.kvm_free and vm.kvm_size for exact figures. >100K buffer memory. If you have e.g. 1GB available to network buffers,=20 >it means a max limit of 10k simultaneous connections on a server,=20 >regardless of how much memory it has. If you want a system to usefully cope with 10K network connections, you will probably want to be running amd64 anyway. That said, Rod Grimes was achieving between 100K and 1M TCP connections to FreeBSD i386 systems in the 1990's. --=20 Peter Jeremy --Qbvjkv9qwOGw/5Fx Content-Type: application/pgp-signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.19 (FreeBSD) iEYEARECAAYFAlBFG3IACgkQ/opHv/APuIde8gCgtEiA5BjFU3khGRk6Ha12suN8 tf8AoLbVrQszZHQjc5ofjS/ywURg8X4J =AwPO -----END PGP SIGNATURE----- --Qbvjkv9qwOGw/5Fx--
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