From: Shrikrishna Khare <skhare@shri-linux.eng.vmware.com>
To: Nachi Prachanda <nprachan@Brocade.com>
Cc: "skhare@vmware.com" <skhare@vmware.com>,
Chas Williams III <ciwillia@Brocade.com>,
"dev@dpdk.org" <dev@dpdk.org>
Subject: Re: [dpdk-dev] [PATCH 1/6] net/vmxnet3: retain counters on restart
Date: Fri, 26 May 2017 10:29:22 -0700 [thread overview]
Message-ID: <alpine.DEB.2.10.1705261027530.5989@shri-linux.eng.vmware.com> (raw)
In-Reply-To: <d9c9fd6c04f7430f9bfab3168a633b2b@Hq1wp-exmb11.corp.brocade.com>
On Thu, 25 May 2017, Nachi Prachanda wrote:
> > From: Shrikrishna Khare [mailto:skhare@shri-linux.eng.vmware.com]
> > Sent: Thursday, May 25, 2017 1:27 PM
> >
> > On Thu, 25 May 2017, Nachi Prachanda wrote:
> >
> > > > From: Shrikrishna Khare [mailto:skhare@shri-linux.eng.vmware.com]
> > > > Sent: Wednesday, May 24, 2017 2:10 PM
> > > >
> > > > On Fri, 19 May 2017, Charles (Chas) Williams wrote:
> > > >
> > > > > From: Nachiketa Prachanda <nprachan@brocade.com>
> > > > >
> > > > > Most nics like virtio, igb/ixgbe etc. don't reset counters on
> > > > > dev_start and arguably this helps in monitoring the counters
> > > > > across a longer time span with multiple device start/stops.
> > > > > vmxnet3 behavior is opposite to that and counters are reset by the
> > > > > host side implementation each time the device is restarted.
> > > > >
> > > > > Change the driver to save the counters in its private context
> > > > > before it is reset by writing CMD_ACTIVATE to REG_CMD.
> > > > >
> > > > > Signed-off-by: Nachiketa Prachanda <nprachan@brocade.com>
> > > >
> > > > This won't be able to deal with vMotion or suspend/resume?
> > >
> > > Correct - this can't deal with the VM suspend/resume unless hypervisor
> > maintains the counter. But this patch doesn't make that behavior any worse
> > than what it was before.
> >
> > The current code always resets stats, but am concerned that this patch will
> > make the behavior inconsistent for cases like suspend/resume.
> >
> > Wondering if this will be better handled by the device emulation instead of the
> > driver (for igb/ixgbe, is this handled by the hardware?).
>
> A little more nuanced.. - see below.
>
> > If we were to handle this in the device emulation, what would be the
> > goals/requirements:
> > - device start/stop should not reset stats?
> > - any other operations where we would like to maintain/reset stats?
> > - what might be the expectation around how accurate the stats need to be?
> > - any other requirement on the device?
>
> I haven't thought about dealing it at the emulation layer - but the expectation
> would be not clear counters not cleared for the lifetime of the device - and have
> a way to clear them from the driver when needed.
>
> don't know if there is a standard behavior about resetting counters. But
> for igb/ixgb the counters are read/clear registers and they are maintained
> at driver. May not be always accurate if the hardware is reset without updating
> the driver's counter - but at least ensures that it is monotonically increasing since
> on each read driver only gets the delta.
>
> virtio emulation doesn't provide the counters - mostly the receive/send functions
> updates the counters.
>
> >
> > Also, note that if we proceed with this patch, and later extend device support
> > to not reset stats, driver with this patch running on the extended device will
> > report incorrect stats.
>
> Agree - it will need some work if the emulation changes.
I spent some time looking at the emulation code. It turns out that these
stats are already retained across vMotion, suspend/resume. And we have no
immediate plan to change the device behavior to retain these stats across
device start/stop. So am fine with this patch. Thank you for being patient
with this.
Thanks,
Shri
>
> Regards,
> Nachi
>
> > Thanks,
> > Shri
>
next prev parent reply other threads:[~2017-05-26 17:29 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-05-19 17:55 Charles (Chas) Williams
2017-05-19 17:55 ` [dpdk-dev] [PATCH 2/6] net/vmxnet3: Implement retrieval of extended stats Charles (Chas) Williams
2017-05-24 0:17 ` Shrikrishna Khare
2017-05-19 17:55 ` [dpdk-dev] [PATCH 3/6] net/vmxnet3: Generate link-state change notifications Charles (Chas) Williams
2017-05-19 17:55 ` [dpdk-dev] [PATCH 4/6] net/vmxnet3: Make vmxnet3_process_events less noisy Charles (Chas) Williams
2017-05-23 21:44 ` Shrikrishna Khare
2017-05-19 17:55 ` [dpdk-dev] [PATCH 5/6] net/vmxnet3: receive queue lockup and memleak Charles (Chas) Williams
2017-06-01 12:24 ` Charles (Chas) Williams
2017-05-24 21:09 ` [dpdk-dev] [PATCH 1/6] net/vmxnet3: retain counters on restart Shrikrishna Khare
2017-05-25 18:31 ` Nachi Prachanda
2017-05-25 20:27 ` Shrikrishna Khare
2017-05-25 22:08 ` Nachi Prachanda
2017-05-26 17:29 ` Shrikrishna Khare [this message]
2017-05-26 19:01 ` Nachi Prachanda
2017-05-26 17:31 ` Shrikrishna Khare
2017-06-15 12:16 ` [dpdk-dev] [PATCH V2 0/6] some local vmxnet3 patches Charles (Chas) Williams
2017-06-15 12:16 ` [dpdk-dev] [PATCH v2 1/6] net/vmxnet3: retain counters on restart Charles (Chas) Williams
2017-06-15 12:16 ` [dpdk-dev] [PATCH v2 2/6] net/vmxnet3: Implement retrieval of extended stats Charles (Chas) Williams
2017-06-21 1:42 ` Shrikrishna Khare
2017-06-15 12:16 ` [dpdk-dev] [PATCH v2 3/6] net/vmxnet3: Generate link-state change notifications Charles (Chas) Williams
2017-06-27 13:52 ` Ferruh Yigit
2017-06-15 12:16 ` [dpdk-dev] [PATCH v2 4/6] net/vmxnet3: Make vmxnet3_process_events less noisy Charles (Chas) Williams
2017-06-28 11:30 ` [dpdk-dev] [PATCH V2 0/6] some local vmxnet3 patches Ferruh Yigit
2017-06-28 12:52 ` Ferruh Yigit
2017-06-28 13:09 ` Charles (Chas) Williams
2017-06-28 17:15 ` Charles (Chas) Williams
2017-06-28 17:54 ` Ferruh Yigit
2017-06-15 12:17 ` [dpdk-dev] [PATCH v2 5/6] net/vmxnet3: receive queue memory leak Charles (Chas) Williams
2017-06-23 23:00 ` Shrikrishna Khare
2017-06-15 12:17 ` [dpdk-dev] [PATCH v2 6/6] net/vmxnet3: preserve configured MAC address Charles (Chas) Williams
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=alpine.DEB.2.10.1705261027530.5989@shri-linux.eng.vmware.com \
--to=skhare@shri-linux.eng.vmware.com \
--cc=ciwillia@Brocade.com \
--cc=dev@dpdk.org \
--cc=nprachan@Brocade.com \
--cc=skhare@vmware.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).