From: Stefan Hajnoczi <stefanha@redhat.com>
To: Jagannathan Raman <jag.raman@oracle.com>
Cc: elena.ufimtseva@oracle.com, fam@euphon.net,
swapnil.ingle@nutanix.com, john.g.johnson@oracle.com,
qemu-devel@nongnu.org, kraxel@redhat.com, quintela@redhat.com,
mst@redhat.com, armbru@redhat.com, kanth.ghatraju@oracle.com,
felipe@nutanix.com, thuth@redhat.com, ehabkost@redhat.com,
konrad.wilk@oracle.com, dgilbert@redhat.com,
liran.alon@oracle.com, thanos.makatos@nutanix.com,
rth@twiddle.net, kwolf@redhat.com, berrange@redhat.com,
mreitz@redhat.com, ross.lagerwall@citrix.com,
marcandre.lureau@gmail.com, pbonzini@redhat.com
Subject: Re: [PATCH v5 32/50] multi-process: Use separate MMIO communication channel
Date: Fri, 6 Mar 2020 16:52:27 +0000 [thread overview]
Message-ID: <20200306165227.GD1438162@stefanha-x1.localdomain> (raw)
In-Reply-To: <d776913e1796fe9f929a665c0265eff3978fcc16.1582576372.git.jag.raman@oracle.com>
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This went unanswered in the last revision:
On Thu, Nov 21, 2019 at 12:31:42PM +0000, Stefan Hajnoczi wrote:
> On Wed, Nov 13, 2019 at 11:14:50AM -0500, Jag Raman wrote:
> > On 11/11/2019 11:21 AM, Stefan Hajnoczi wrote:
> > > On Thu, Oct 24, 2019 at 05:09:13AM -0400, Jagannathan Raman wrote:
> > > > Using a separate communication channel for MMIO helps
> > > > with improving Performance
> > >
> > > Why?
> >
> > Typical initiation of IO operations involves multiple MMIO accesses per
> > IO operation. In some legacy devices like LSI, the completion of the IO
> > operations is also accomplished by polling on MMIO registers. Therefore,
> > MMIO traffic can be hefty in some cases and contribute to Performance.
> >
> > Having a dedicated channel for MMIO ensures that it doesn't have to
> > compete with other messages to the remote process, especially when there
> > are multiple devices emulated by a single remote process.
>
> A vCPU doing a polling read on an MMIO register will cause a BAR_READ
> message to be sent to the remote process. The vCPU thread waits for the
> response to this message.
>
> When there are multiple remote devices each has its own socket, so
> communication with different remote processes does not interfere.
>
> The only scenarios I can think of are:
> 1. Interference within a single device between vCPUs and/or the QEMU
> monitor.
> 2. A single process serving multiple devices that is implemented in a
> way such that different devices interfere with each other.
>
> It sounds like you are saying the problem is #2, but this is still
> unclear to me. If the remote process can be implemented in a way such
> that there is no interference when each device has a special MMIO
> socket, then why can't it be implemented in a way such that there is no
> interference when each device's main socket is used (each device has
> it's own!).
>
> Maybe I've missed the point. It would be good if you could explain in
> more detail.
>
> Stefan
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next prev parent reply other threads:[~2020-03-06 16:53 UTC|newest]
Thread overview: 117+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-24 20:54 [PATCH v5 00/50] Initial support for multi-process qemu Jagannathan Raman
2020-02-24 20:54 ` [PATCH v5 01/50] multi-process: memory: alloc RAM from file at offset Jagannathan Raman
2020-03-03 19:51 ` Dr. David Alan Gilbert
2020-03-04 18:24 ` Jag Raman
2020-02-24 20:54 ` [PATCH v5 02/50] multi-process: Refactor machine_init and exit notifiers Jagannathan Raman
2020-03-29 16:45 ` Marc-André Lureau
2020-02-24 20:54 ` [PATCH v5 03/50] multi-process: add a command line option for debug file Jagannathan Raman
2020-02-24 20:54 ` [PATCH v5 04/50] multi-process: Add stub functions to facilate build of multi-process Jagannathan Raman
2020-02-24 20:54 ` [PATCH v5 05/50] multi-process: Add config option for multi-process QEMU Jagannathan Raman
2020-02-24 20:54 ` [PATCH v5 06/50] multi-process: build system for remote device process Jagannathan Raman
2020-02-24 20:54 ` [PATCH v5 07/50] multi-process: define mpqemu-link object Jagannathan Raman
2020-03-10 16:09 ` Stefan Hajnoczi
2020-03-10 18:26 ` Elena Ufimtseva
2020-03-16 11:26 ` Stefan Hajnoczi
2020-02-24 20:54 ` [PATCH v5 08/50] multi-process: add functions to synchronize proxy and remote endpoints Jagannathan Raman
2020-03-03 19:56 ` Dr. David Alan Gilbert
2020-03-04 18:42 ` Jag Raman
2020-03-04 19:46 ` Dr. David Alan Gilbert
2020-02-24 20:55 ` [PATCH v5 09/50] multi-process: setup PCI host bridge for remote device Jagannathan Raman
2020-02-24 20:55 ` [PATCH v5 10/50] multi-process: setup a machine object for remote device process Jagannathan Raman
2020-02-24 20:55 ` [PATCH v5 11/50] multi-process: setup memory manager for remote device Jagannathan Raman
2020-02-24 20:55 ` [PATCH v5 12/50] multi-process: remote process initialization Jagannathan Raman
2020-03-04 10:29 ` Dr. David Alan Gilbert
2020-03-04 18:45 ` Jag Raman
2020-03-04 19:00 ` Dr. David Alan Gilbert
2020-02-24 20:55 ` [PATCH v5 13/50] multi-process: introduce proxy object Jagannathan Raman
2020-02-24 20:55 ` [PATCH v5 14/50] mutli-process: build remote command line args Jagannathan Raman
2020-03-02 17:36 ` Philippe Mathieu-Daudé
2020-03-02 17:47 ` Daniel P. Berrangé
2020-03-02 22:39 ` Elena Ufimtseva
2020-03-04 11:00 ` Daniel P. Berrangé
2020-03-04 16:25 ` Elena Ufimtseva
2020-03-04 16:33 ` Daniel P. Berrangé
2020-03-04 22:37 ` Elena Ufimtseva
2020-03-05 8:21 ` Daniel P. Berrangé
2020-03-06 16:25 ` Stefan Hajnoczi
2020-03-04 10:09 ` Dr. David Alan Gilbert
2020-02-24 20:55 ` [PATCH v5 15/50] multi-process: PCI BAR read/write handling for proxy & remote endpoints Jagannathan Raman
2020-03-04 10:47 ` Dr. David Alan Gilbert
2020-03-04 19:05 ` Jag Raman
2020-02-24 20:55 ` [PATCH v5 16/50] multi-process: Synchronize remote memory Jagannathan Raman
2020-03-04 11:53 ` Dr. David Alan Gilbert
2020-03-04 19:35 ` Jag Raman
2020-02-24 20:55 ` [PATCH v5 17/50] multi-process: create IOHUB object to handle irq Jagannathan Raman
2020-02-24 20:55 ` [PATCH v5 18/50] multi-process: configure remote side devices Jagannathan Raman
2020-02-24 20:55 ` [PATCH v5 19/50] multi-process: Retrieve PCI info from remote process Jagannathan Raman
2020-02-24 20:55 ` [PATCH v5 20/50] multi-process: add qdev_proxy_add to create proxy devices Jagannathan Raman
2020-02-24 20:55 ` [PATCH v5 21/50] multi-process: remote: add setup_devices msg processing Jagannathan Raman
2020-02-24 20:55 ` [PATCH v5 22/50] multi-process: remote: use fd for socket from parent process Jagannathan Raman
2020-02-24 20:55 ` [PATCH v5 23/50] multi-process: remote: add create_done condition Jagannathan Raman
2020-02-24 20:55 ` [PATCH v5 24/50] multi-process: add processing of remote device command line Jagannathan Raman
2020-02-24 20:55 ` [PATCH v5 25/50] multi-process: Introduce build flags to separate remote process code Jagannathan Raman
2020-02-24 20:55 ` [PATCH v5 26/50] multi-process: refractor vl.c code Jagannathan Raman
2020-02-24 20:55 ` [PATCH v5 27/50] multi-process: add remote option Jagannathan Raman
2020-02-24 20:55 ` [PATCH v5 28/50] multi-process: add remote options parser Jagannathan Raman
2020-02-24 20:55 ` [PATCH v5 29/50] multi-process: add parse_cmdline in remote process Jagannathan Raman
2020-02-24 20:55 ` [PATCH v5 30/50] multi-process: send heartbeat messages to remote Jagannathan Raman
2020-02-24 20:55 ` [PATCH v5 31/50] multi-process: handle heartbeat messages in remote process Jagannathan Raman
2020-02-24 20:55 ` [PATCH v5 32/50] multi-process: Use separate MMIO communication channel Jagannathan Raman
2020-03-06 16:52 ` Stefan Hajnoczi [this message]
2020-03-10 18:04 ` Jag Raman
2020-02-24 20:55 ` [PATCH v5 33/50] multi-process: perform device reset in the remote process Jagannathan Raman
2020-02-24 20:55 ` [PATCH v5 34/50] multi-process/mon: choose HMP commands based on target Jagannathan Raman
2020-03-05 10:39 ` Dr. David Alan Gilbert
2020-03-05 15:38 ` Jag Raman
2020-03-05 15:50 ` Dr. David Alan Gilbert
2020-02-24 20:55 ` [PATCH v5 35/50] multi-process/mon: stub functions to enable QMP module for remote process Jagannathan Raman
2020-02-24 20:55 ` [PATCH v5 36/50] multi-process/mon: enable QMP module support in the " Jagannathan Raman
2020-03-05 10:43 ` Dr. David Alan Gilbert
2020-03-05 15:40 ` Jag Raman
2020-03-05 15:52 ` Dr. David Alan Gilbert
2020-02-24 20:55 ` [PATCH v5 37/50] multi-process/mon: Refactor monitor/chardev functions out of vl.c Jagannathan Raman
2020-03-05 10:51 ` Dr. David Alan Gilbert
2020-03-05 15:41 ` Jag Raman
2020-02-24 20:55 ` [PATCH v5 38/50] multi-process/mon: Initialize QMP module for remote processes Jagannathan Raman
2020-02-24 20:55 ` [PATCH v5 39/50] multi-process: prevent duplicate memory initialization in remote Jagannathan Raman
2020-02-24 20:55 ` [PATCH v5 40/50] multi-process/mig: build migration module in the remote process Jagannathan Raman
2020-03-04 15:58 ` Dr. David Alan Gilbert
2020-03-04 19:45 ` Jag Raman
2020-03-04 19:52 ` Dr. David Alan Gilbert
2020-03-04 20:23 ` Jag Raman
2020-03-05 10:10 ` Dr. David Alan Gilbert
2020-03-05 17:07 ` Elena Ufimtseva
2020-03-05 17:19 ` Dr. David Alan Gilbert
2020-02-24 20:55 ` [PATCH v5 41/50] multi-process/mig: Enable VMSD save in the Proxy object Jagannathan Raman
2020-03-05 12:31 ` Dr. David Alan Gilbert
2020-03-05 16:48 ` Jag Raman
2020-03-05 17:04 ` Dr. David Alan Gilbert
2020-02-24 20:55 ` [PATCH v5 42/50] multi-process/mig: Send VMSD of remote to " Jagannathan Raman
2020-03-05 14:39 ` Dr. David Alan Gilbert
2020-03-05 16:32 ` Elena Ufimtseva
2020-02-24 20:55 ` [PATCH v5 43/50] multi-process/mig: Load VMSD in the proxy object Jagannathan Raman
2020-03-05 15:28 ` Dr. David Alan Gilbert
2020-02-24 20:55 ` [PATCH v5 44/50] multi-process/mig: refactor runstate_check into common file Jagannathan Raman
2020-02-24 20:55 ` [PATCH v5 45/50] multi-process/mig: Synchronize runstate of remote process Jagannathan Raman
2020-02-24 20:55 ` [PATCH v5 46/50] multi-process/mig: Restore the VMSD in " Jagannathan Raman
2020-03-05 16:05 ` Dr. David Alan Gilbert
2020-02-24 20:55 ` [PATCH v5 47/50] multi-process: Enable support for multiple devices in remote Jagannathan Raman
2020-02-28 16:44 ` Stefan Hajnoczi
2020-03-02 19:28 ` Jag Raman
2020-02-24 20:55 ` [PATCH v5 48/50] multi-process: Validate incoming commands from Proxy Jagannathan Raman
2020-02-27 17:18 ` Stefan Hajnoczi
2020-02-28 17:53 ` Elena Ufimtseva
2020-02-24 20:55 ` [PATCH v5 49/50] multi-process: add the concept description to docs/devel/qemu-multiprocess Jagannathan Raman
2020-02-27 17:11 ` Stefan Hajnoczi
2020-02-28 18:44 ` Elena Ufimtseva
2020-02-24 20:55 ` [PATCH v5 50/50] multi-process: add configure and usage information Jagannathan Raman
2020-02-27 16:58 ` Stefan Hajnoczi
2020-02-28 18:43 ` Elena Ufimtseva
2020-03-06 16:42 ` Stefan Hajnoczi
2020-02-24 21:59 ` [PATCH v5 00/50] Initial support for multi-process qemu no-reply
2020-02-24 22:03 ` no-reply
2020-02-24 22:23 ` no-reply
2020-03-01 11:57 ` Alex Bennée
2020-03-02 15:28 ` Jag Raman
2020-03-02 16:29 ` Alex Bennée
2020-03-02 16:53 ` Jag Raman
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