Date: Mon, 10 Oct 2016 22:27:07 +0300 From: Slawa Olhovchenkov <slw@zxy.spb.ru> To: John Baldwin <jhb@freebsd.org> Cc: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-stable@freebsd.org, svn-src-stable-11@freebsd.org Subject: Re: svn commit: r306661 - in stable/11/sys/dev/cxgbe: . tom Message-ID: <20161010192707.GC54003@zxy.spb.ru> In-Reply-To: <4497031.RrIpxcHyXF@ralph.baldwin.cx> References: <201610032315.u93NFiHE057529@repo.freebsd.org> <5243602.cilUCEM5cP@ralph.baldwin.cx> <20161010184357.GB54003@zxy.spb.ru> <4497031.RrIpxcHyXF@ralph.baldwin.cx>
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On Mon, Oct 10, 2016 at 12:21:14PM -0700, John Baldwin wrote: > On Monday, October 10, 2016 09:43:57 PM Slawa Olhovchenkov wrote: > > On Mon, Oct 10, 2016 at 11:39:24AM -0700, John Baldwin wrote: > > > > > On Monday, October 10, 2016 09:28:21 PM Slawa Olhovchenkov wrote: > > > > On Mon, Oct 10, 2016 at 10:46:27AM -0700, John Baldwin wrote: > > > > > > > > > On Monday, October 10, 2016 02:09:01 PM Slawa Olhovchenkov wrote: > > > > > > On Mon, Oct 03, 2016 at 11:15:44PM +0000, John Baldwin wrote: > > > > > > > > > > > > > Author: jhb > > > > > > > Date: Mon Oct 3 23:15:44 2016 > > > > > > > New Revision: 306661 > > > > > > > URL: https://svnweb.freebsd.org/changeset/base/306661 > > > > > > > > > > > > > > Log: > > > > > > > MFC 303405: Add support for zero-copy aio_write() on TOE sockets. > > > > > > > > > > > > > > AIO write requests for a TOE socket on a Chelsio T4+ adapter can now > > > > > > > DMA directly from the user-supplied buffer. This is implemented by > > > > > > > wiring the pages backing the user-supplied buffer and queueing special > > > > > > > mbufs backed by raw VM pages to the socket buffer. The TOE code > > > > > > > recognizes these special mbufs and builds a sglist from the VM page > > > > > > > array associated with the mbuf when queueing a work request to the TOE. > > > > > > > > > > > > > > Because these mbufs do not have an associated virtual address, m_data > > > > > > > is not valid. Thus, the AIO handler does not invoke sosend() directly > > > > > > > for these mbufs but instead inlines portions of sosend_generic() and > > > > > > > tcp_usr_send(). > > > > > > > > > > > > > > An aiotx_buffer structure is used to describe the user buffer (e.g. > > > > > > > it holds the array of VM pages and a reference to the AIO job). The > > > > > > > special mbufs reference this structure via m_ext. Note that a single > > > > > > > job might be split across multiple mbufs (e.g. if it is larger than > > > > > > > the socket buffer size). The 'ext_arg2' member of each mbuf gives an > > > > > > > offset relative to the backing aiotx_buffer. The AIO job associated > > > > > > > with an aiotx_buffer structure is completed when the last reference to > > > > > > > the structure is released. > > > > > > > > > > > > > > Zero-copy aio_write()'s for connections associated with a given > > > > > > > adapter can be enabled/disabled at runtime via the > > > > > > > 'dev.t[45]nex.N.toe.tx_zcopy' sysctl. > > > > > > > > > > > > > > Sponsored by: Chelsio Communications > > > > > > > > > > > > Do you have any public available application patches for support this? > > > > > > May be nginx? > > > > > > > > > > Applications need to use aio_read(), ideally with at least 2 buffers (so > > > > > queue two reads, then when a read completes, consume the data and do the > > > > > next read). I'm not sure nginx will find this but so useful as web servers > > > > > tend to send a lot more data than they receive. The only software I have > > > > > patched explicitly for this is netperf. > > > > > > > > Hm, this is like only aio_read() on sokets give performance boost, not > > > > aio_write()? > > > > > > Sorry, I was confused on the commit, this does affect aio_write() (earlier > > > changes also permit zero-copy for receive via aio_read()). However, as you > > > noted in the reply to Navdeep, it seems that nginx only supports using > > > AIO on the backing files for static content it seems. It would need changes > > > to support using aio_write on sockets (similar to using sendfile). > > > > Thanks > > You don't planed to do this? > > After talking with Navdeep it looks like I will take a stab at adding support > for this and seeing what effects it has. For static content workloads using > sendfile I'm not sure it will be a win, but it might let you avoid some of > the CPU cycles for dynamically-generated content by avoiding copies for those. As I remember you tests show performance boost over sendfile. Also, sendfile over ZFS don't work good, as I remember (readahead don't work, at least).
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