Date: Thu, 23 Jan 2020 20:33:58 -0500 From: Ryan Stone <rysto32@gmail.com> To: Gleb Smirnoff <glebius@freebsd.org> Cc: src-committers <src-committers@freebsd.org>, svn-src-all <svn-src-all@freebsd.org>, svn-src-head <svn-src-head@freebsd.org> Subject: Re: svn commit: r357051 - head/sys/dev/bge Message-ID: <CAFMmRNz3TVPfP7_fhBMa=gdN%2BM4OdCco3z1qO=mPOm57-QOsng@mail.gmail.com> In-Reply-To: <20200124012458.GI1268@FreeBSD.org> References: <202001231636.00NGawrr080128@repo.freebsd.org> <CAFMmRNyP5nKPZ62c9yRktH4t23GAgnpc2u8kHhUevUCu3doAQQ@mail.gmail.com> <20200123230546.GG1268@FreeBSD.org> <CAFMmRNwhcV-%2BSsq_a1RZJYXC8wvnUDLDxdFeHD7PgL5wuierkg@mail.gmail.com> <20200124012458.GI1268@FreeBSD.org>
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On Thu, Jan 23, 2020 at 8:25 PM Gleb Smirnoff <glebius@freebsd.org> wrote: > Because at interrupt level we can batch multiple packets in a single epoch. > This speeds up unfiltered packet forwarding performance by 5%. > > With driver level pfil hooks I would claim even more improvement, because before > the change we needed to enter epoch twice - once for filtering, than for ether_input. > > Epoch isn't a layer, it is a synchronisation primitive, so I disagree about > statement on layering violation. Epoch is a synchronization primitive, but the net_epoch is absolutely a part of the networking layer. If we need better batching then the correct solution is to introduce a batched interface for drivers to push packets up the stack, not to mess around at the interrupt layer. Note that the only reason why this works for mlx4/mlx5 is that linuxkpi *always* requests a INTR_TYPE_NET no matter what driver is running. This means that all drm graphics driver interrupts are now running under the net_epoch: https://svnweb.freebsd.org/base/head/sys/compat/linuxkpi/common/include/linux/interrupt.h?revision=352205&view=markup#l103
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