[nvmewin] review comments for patch from Google

Robles, Raymond C raymond.c.robles at intel.com
Fri Aug 26 11:27:08 PDT 2016 

All reviewers,

The concurrent channels patch from Google has been out for review for just over a month. I extended the time to review to provide companies ample time to review/test.

Intel has still found the same issues as before with the latest zipped source code sent from Google…


·         Not on the latest branch (missing namespace management code), and

·         Missing call to StorPortGetStartIoPerfParams() to get the STARTIO_PERFORMANCE_PARAMETERS in order to identify the current MSI-x vector number (in order to get the correct SQ on which to submit the command).

In lieu of this, I would like to propose two options concerning our mid-year release:


1.       Move forward with the mid-year release and hold off on resolving the concurrent channels patch from Google until after the release, or

2.       Resolve the current concurrent channels patch first, and then release (this will delay our targeted end of August release timeframe).

Please cast your vote for which option you choose. Note that Intel is in favor of option 1.


·         HGST: TBD

·         Intel: Option 1

·         Samsung: TBD

If there are other suggestions for the mid-year release, please feel free to suggest.

Thank you…
Ray

From: Iuliu Rus [mailto:iuliur at google.com]
Sent: Friday, July 08, 2016 12:52 PM
To: Robles, Raymond C <raymond.c.robles at intel.com>
Cc: Foster, Carolyn D <carolyn.d.foster at intel.com>; nvmewin <nvmewin at lists.openfabrics.org>
Subject: Re: [nvmewin] review comments for patch from Google

Password is nvme

On Fri, Jul 8, 2016 at 12:25 PM, Robles, Raymond C <raymond.c.robles at intel.com<mailto:raymond.c.robles at intel.com>> wrote:
Hi Iuliu,

As Carolyn suggested below, you will have to encrypt (password protect) your zip file. Many company firewalls (i.e. Intel) will block .c/.h files.

Could you please rezip your source code and add encryption/password protection, and resend? Don’t forget to send the password as well.

Thanks!
Ray

From: Iuliu Rus [mailto:iuliur at google.com<mailto:iuliur at google.com>]
Sent: Friday, July 08, 2016 12:23 PM
To: Robles, Raymond C <raymond.c.robles at intel.com<mailto:raymond.c.robles at intel.com>>
Cc: Foster, Carolyn D <carolyn.d.foster at intel.com<mailto:carolyn.d.foster at intel.com>>; nvmewin <nvmewin at lists.openfabrics.org<mailto:nvmewin at lists.openfabrics.org>>
Subject: Re: [nvmewin] review comments for patch from Google

I did, but some of your e-mail servers rejected it, even after changing the extension.

On Fri, Jul 8, 2016 at 12:20 PM, Robles, Raymond C <raymond.c.robles at intel.com<mailto:raymond.c.robles at intel.com>> wrote:
Hi Iuliu,

Did you ever send out your zipped source code?

Thank you…
Ray

From: Foster, Carolyn D
Sent: Wednesday, June 29, 2016 4:45 PM
To: Iuliu Rus <iuliur at google.com<mailto:iuliur at google.com>>; Robles, Raymond C <raymond.c.robles at intel.com<mailto:raymond.c.robles at intel.com>>
Cc: nvmewin <nvmewin at lists.openfabrics.org<mailto:nvmewin at lists.openfabrics.org>>
Subject: RE: [nvmewin] review comments for patch from Google

Hi Iuliu,
Can you please zip your local source files and send it out to the group?  You might want to encrypt it and provide us with the password.

Thanks!
Carolyn

From: nvmewin [mailto:nvmewin-bounces at lists.openfabrics.org] On Behalf Of Iuliu Rus
Sent: Wednesday, June 29, 2016 4:20 PM
To: Robles, Raymond C <raymond.c.robles at intel.com<mailto:raymond.c.robles at intel.com>>
Cc: nvmewin <nvmewin at lists.openfabrics.org<mailto:nvmewin at lists.openfabrics.org>>
Subject: Re: [nvmewin] review comments for patch from Google

I think i don't understand how patching works. Did you sync up your local copy before looking at it? I did not remove those lines, they are still present in my local copy.

On Wed, Jun 29, 2016 at 3:44 PM, Robles, Raymond C <raymond.c.robles at intel.com<mailto:raymond.c.robles at intel.com>> wrote:
Hi Iuliu,

Thanks for the updated patch. After reviewing again, I have some additional questions…


•         In ProcessIo, the dpc lock is obtained later in the code than originally implemented. Why move the lock acquire down?

•         In ProcessIo, it appears that you do not call StorPortGetStartIoPerfParams() to obtain the completing MSI-x message number. Getting this MSI-x message number ensures that you know which interrupt vector will be used to complete this request… and therefore you know on which SQ/CQ pair to post the SQE. Was this left out intentionally? See sample code below:


if (((DeviceExtension->perfData.Flags & STOR_PERF_INTERRUPT_MESSAGE_RANGES) == STOR_PERF_INTERRUPT_MESSAGE_RANGES) &&
(SrbExtension->pSrb != NULL)) {
Perf.Size = sizeof(STARTIO_PERFORMANCE_PARAMETERS);
StorPortGetStartIoPerfParams((PVOID)DeviceExtension,
(PSCSI_REQUEST_BLOCK)pSrbExtension->pSrb,
&Perf);
StorStatus = NVMeMapMsiToQueue(DeviceExtension,
Perf.MessageNumber,
&SubQueue,
&CplQueue);



•         When setting up concurrent channels, I do not see the Storport Perf Opts changes from Suman’s patch (Samsung). The Perf Opts changes replace the old learning mode and drive the source core interrupt steering in the driver. Without it, the concurrent channels changes will not be optimized correctly. See reference to Perf Opts setup code (directly from OFA source trunk in NVMeInitialize) below:


if (pAE->ntldrDump == FALSE) {
        /* Enumerate granted MSI/MSI-X messages if there is any */
        if (NVMeEnumMsiMessages(pAE) == FALSE) {
            NVMeFreeBuffers(pAE);
            return (FALSE);
        }
           perfQueryData.Version = STOR_PERF_VERSION;
           perfQueryData.Size = sizeof(PERF_CONFIGURATION_DATA);
           Status = StorPortInitializePerfOpts(pAE, TRUE, &perfQueryData);
           ASSERT(STOR_STATUS_SUCCESS == Status);
           if (STOR_STATUS_SUCCESS == Status) {

                perfData.Version = STOR_PERF_VERSION;
                perfData.Size = sizeof(PERF_CONFIGURATION_DATA);

                /* Allow optimization of storport DPCs */
                if (perfQueryData.Flags & STOR_PERF_DPC_REDIRECTION) {
                     perfData.Flags = STOR_PERF_DPC_REDIRECTION;

                     /* Allow optimization of Interrupt Redirection and Group Affinity */
                     if ((perfQueryData.Flags & (STOR_PERF_INTERRUPT_MESSAGE_RANGES | STOR_PERF_ADV_CONFIG_LOCALITY)) ==
                           (STOR_PERF_INTERRUPT_MESSAGE_RANGES | STOR_PERF_ADV_CONFIG_LOCALITY)){
                           perfData.Flags |= STOR_PERF_INTERRUPT_MESSAGE_RANGES;
                           perfData.Flags |= STOR_PERF_ADV_CONFIG_LOCALITY;

                           perfData.FirstRedirectionMessageNumber = 0;
                           perfData.LastRedirectionMessageNumber = (pRMT->NumMsiMsgGranted - 1);
                           perfData.MessageTargets = pAE->pArrGrpAff;
                     }
                }

                Status = StorPortInitializePerfOpts(pAE, FALSE, &perfData);
                ASSERT(STOR_STATUS_SUCCESS == Status);
                if (STOR_STATUS_SUCCESS == Status){
                     pAE->IsMsiMappingComplete = TRUE;
                }
           }

        /* Call StorPortPassiveInitialization to enable passive init */
        StorPortEnablePassiveInitialization(pAE, NVMePassiveInitialize);

        return (TRUE);
    } else {



Thank you…
Ray



From: Iuliu Rus [mailto:iuliur at google.com<mailto:iuliur at google.com>]
Sent: Wednesday, June 29, 2016 10:56 AM
To: Thomas Freeman <thomas.freeman at hgst.com<mailto:thomas.freeman at hgst.com>>
Cc: Robles, Raymond C <raymond.c.robles at intel.com<mailto:raymond.c.robles at intel.com>>; nvmewin <nvmewin at lists.openfabrics.org<mailto:nvmewin at lists.openfabrics.org>>
Subject: Re: [nvmewin] review comments for patch from Google

Sorry about Thomas. I resolved that conflict but i think i sent you the patch pre-resolve by mistake. Here is the correct patch. I also triggered the RecoveryDpc from the debugger, to make sure i have coverage on that. I don't think the normal tests cover it.


On Wed, Jun 29, 2016 at 7:25 AM, Thomas Freeman <thomas.freeman at hgst.com<mailto:thomas.freeman at hgst.com>> wrote:
Iuliu,
It looks like the patch file has an unresolved conflict:

+<<<<<<< .mine
+                             ReleaseDpcSpinLocks(pAE, dpcLocks);
+             }  /* reset the controller */
+             if (pAE->NumDpc > MAX_DPC) {
+                             StorPortFreePool(pHwDeviceExtension, dpcLocks);
+             }
+||||||| .r137
+        StorPortReleaseSpinLock(pAE, &startLockhandle);
+    }  /* reset the controller */
+=======
                               pAE->DeviceRemovedDuringIO = TRUE;
#if (NTDDI_VERSION > NTDDI_WIN7)
                               if (pAE->Timerhandle != NULL) {
@@ -2634,6 +2680,7 @@
         NVMeFreeBuffers(pAE);
                               StorPortResume(pAE);
     }  /* reset the controller */
+>>>>>>> .r139



Tom Freeman
Software Engineer, Device Manager and Driver Development
Western Digital Corporation
e.  Thomas.freeman at hgst.com<mailto:Thomas.freeman at hgst.com>
o.  +1-507-322-2311<tel:%2B1-507-322-2311>

[cid:image001.jpg at 01D1D1F7.245A73D0]

From: nvmewin [mailto:nvmewin-bounces at lists.openfabrics.org<mailto:nvmewin-bounces at lists.openfabrics.org>] On Behalf Of Iuliu Rus
Sent: Monday, June 27, 2016 11:12 AM
To: Robles, Raymond C <raymond.c.robles at intel.com<mailto:raymond.c.robles at intel.com>>
Cc: nvmewin <nvmewin at lists.openfabrics.org<mailto:nvmewin at lists.openfabrics.org>>
Subject: Re: [nvmewin] review comments for patch from Google

Done.

On Mon, Jun 27, 2016 at 8:52 AM, Robles, Raymond C <raymond.c.robles at intel.com<mailto:raymond.c.robles at intel.com>> wrote:
Hi Suman,

Thank you for checking on your patches. I was unaware that your latest patch for IOCTL Surprise Removal was not applied correctly. I’ve just applied that patch again and the trunk should now be at revision 138. Could you please double check to ensure you patch is applied properly and let me know? Thank you!!!

Hi Iuliu,

Sorry about the thrash… but I think we’ve finally got the trunk up to date to the latest (once confirmed by Suman from Samsung). Once confirmed, please rebase you trunk and add your modifications to that latest revision (138). Thank you!!!

Thanks…
Ray

From: SUMAN PRAKASH B [mailto:suman.p at samsung.com<mailto:suman.p at samsung.com>]
Sent: Monday, June 27, 2016 1:12 AM
To: Robles, Raymond C <raymond.c.robles at intel.com<mailto:raymond.c.robles at intel.com>>; Iuliu Rus <iuliur at google.com<mailto:iuliur at google.com>>
Cc: nvmewin <nvmewin at lists.openfabrics.org<mailto:nvmewin at lists.openfabrics.org>>
Subject: Re: Re: [nvmewin] review comments for patch from Google


Hi Ray,



Samsung submitted 3 patches. Revision 134 is first patch, Revision 136 and 137 is second patch.

We submitted third patch for Handling device Surprise removal in IOCTL path which was approved by HGST and Intel on 1st June. Please find attached the mail thread for reference.

The third patch is not yet checked-in to trunk.



Thanks,

Suman



------- Original Message -------

Sender : Robles, Raymond C<raymond.c.robles at intel.com<mailto:raymond.c.robles at intel.com>>

Date : Jun 27, 2016 12:19 (GMT+05:30)

Title : Re: [nvmewin] review comments for patch from Google


Hi Iuliu,

I apologize for the delay in responding. I was performing a manual diff of the last several merges to complete the investigation. Here is what I found.

The latest revision on the OFA source trunk is actually 137 (refer to my screenshot below). I’ve manually gone back and made sure that all the patches submitted are in this latest revision. I found no errors or issues. The latest trunk is up to date with all of the patches. If you were trying to apply your patch yourself, you cannot. Only myself (OFA co-chair) and Carolyn Foster (OFA source maintainer) have write permissions to the repo.

Each patch listed below is applied to trunk. The only think you need to insure is that your latest concurrent channels modifications are based off the 137 revision. If you have any questions, please me know.

Here is the screenshot of all the patches I’ve checked…


[cid:image002.png at 01D1D1F7.245A73D0]


Thank you…
Ray

From: nvmewin [mailto:nvmewin-bounces at lists.openfabrics.org<mailto:nvmewin-bounces at lists.openfabrics.org>] On Behalf Of Robles, Raymond C
Sent: Friday, June 17, 2016 12:08 PM
To: Iuliu Rus <iuliur at google.com<mailto:iuliur at google.com>>
Cc: nvmewin <nvmewin at lists.openfabrics.org<mailto:nvmewin at lists.openfabrics.org>>
Subject: Re: [nvmewin] review comments for patch from Google

Thanks Iuliu. I’m currently investigating the issue. Will let everyone know when the trunk is updated.

Thank you…
Ray

From: Iuliu Rus [mailto:iuliur at google.com]
Sent: Friday, June 17, 2016 10:29 AM
To: Robles, Raymond C <raymond.c.robles at intel.com<mailto:raymond.c.robles at intel.com>>
Cc: Thomas Freeman <thomas.freeman at hgst.com<mailto:thomas.freeman at hgst.com>>; nvmewin <nvmewin at lists.openfabrics.org<mailto:nvmewin at lists.openfabrics.org>>
Subject: Re: [nvmewin] review comments for patch from Google

I don't see any changes when i try to update. My svn says : completed at revision 137.

On Thu, Jun 16, 2016 at 2:42 PM, Robles, Raymond C <raymond.c.robles at intel.com<mailto:raymond.c.robles at intel.com>> wrote:
Hi Iuliu- Please rebase your patch with the latest OFA trunk source. If you do not see any updates during your rebase, please let me know and I’ll investigate. Thanks!

From: Iuliu Rus [mailto:iuliur at google.com<mailto:iuliur at google.com>]
Sent: Thursday, June 16, 2016 2:15 PM
To: Robles, Raymond C <raymond.c.robles at intel.com<mailto:raymond.c.robles at intel.com>>
Cc: Thomas Freeman <thomas.freeman at hgst.com<mailto:thomas.freeman at hgst.com>>; nvmewin <nvmewin at lists.openfabrics.org<mailto:nvmewin at lists.openfabrics.org>>

Subject: Re: [nvmewin] review comments for patch from Google

Let me know if i have to sync to the latest and re-do the patch.

On Thu, Jun 16, 2016 at 2:10 PM, Iuliu Rus <iuliur at google.com<mailto:iuliur at google.com>> wrote:
We already have a pool of locks - the dpc locks, which is what i'm using in my latest patch. You cannot create spinlocks directly in a storport driver, the only option is to use either the StartIoLock, the dpc lock, the interrupt lock or one of the MSI locks.

On Thu, Jun 16, 2016 at 2:04 PM, Robles, Raymond C <raymond.c.robles at intel.com<mailto:raymond.c.robles at intel.com>> wrote:
Hello,

Here are my thoughts…

In short, I agree with Thomas’s assessment.

Concurrent channels allows Storport to call StartIo concurrently… and with no locks. Therefore the locking of critical sections is now the responsibility of the miniport.

Any solution proposed should protect critical resources (cmd id pool, cmd entries, doorbells) with a lock that is granular enough for our driver, but not at the visibility of the OS or Storport. Acquiring the StartIo lock to protect resources in our driver only is too broad of a lock. My suggestion would be to create a pool of locks (one for every SQ/CQ pair) that is maintained within our driver. Again, crashdump mode is a non-issue because it is single threaded.

Thank you…
Ray

From: Thomas Freeman [mailto:thomas.freeman at hgst.com<mailto:thomas.freeman at hgst.com>]
Sent: Thursday, June 16, 2016 1:51 PM
To: Iuliu Rus <iuliur at google.com<mailto:iuliur at google.com>>
Cc: Robles, Raymond C <raymond.c.robles at intel.com<mailto:raymond.c.robles at intel.com>>; nvmewin <nvmewin at lists.openfabrics.org<mailto:nvmewin at lists.openfabrics.org>>
Subject: RE: [nvmewin] review comments for patch from Google

Hi Iuliu,
Here my view, I hope someone else can chime in to verify or correct what I'm saying

The purpose of the concurrent channels change is to prevent Storport from acquiring the StartIo lock before calling Startio. This allows multiple simultaneous calls to StartIo. If you require ProcessIo get the StartIo lock, you are replicating what Storport used to - it defeats the point of concurrent channels.

Here is my suggestion for what needs to be changed
1. There is no need for StartIo Locks - remove the requests to acquire them
2. Acquire the Dpc locks in the following situations
   -ProcessIo, before calling GetCmdEntry - if there is queue sharing
   -ProcessIo, before calling IssueCmd - always
   -IoCompletionRoutine, before calling NVMeCompleteCmd - if there is queue sharing

   -recoveryDpcRoutine - get all of the Dpc locks


Here is my reasoning
-GetCmdEntry and NVMeCompleteCmd both access the FreeQList. With queue sharing, these could run simultaneously and have a collision when they update the list.
-IssueCmd. With queue sharing, different cpu's could attempt to put entries on the queue simultaneously. But, to make RecoveryDpcRoutine work, this must be protected by the dpcLock whether or not there is queue sharing.

I think this will address the deadlock problem I reported also.

Regards,
Tom Freeman
Software Engineer, Device Manager and Driver Development
Western Digital Corporation
e.  Thomas.freeman at hgst.com<mailto:Thomas.freeman at hgst.com>
o.  +1-507-322-2311<tel:%2B1-507-322-2311>

[cid:image001.jpg at 01D1D1F7.245A73D0]

From: Iuliu Rus [mailto:iuliur at google.com]
Sent: Thursday, June 16, 2016 2:42 PM
To: Thomas Freeman <thomas.freeman at hgst.com<mailto:thomas.freeman at hgst.com>>
Cc: Robles, Raymond C <raymond.c.robles at intel.com<mailto:raymond.c.robles at intel.com>>; nvmewin <nvmewin at lists.openfabrics.org<mailto:nvmewin at lists.openfabrics.org>>
Subject: Re: [nvmewin] review comments for patch from Google

Here's my revised patch for concurrent channels. The synchronization rules are now as follows:
1. Init is single threaded so it doesn't matter if acquirelock is true or false
2. Anything called from the DPC has to call ProcessIo with false, since the dpc spinlock is already acquired.
3. Anything called from StartIo has to call ProcessIo with true, since now the startio is not automatically acquired.

Thomas, i think the bug that you found is because the ProcessIo was incorrectly called with TRUE instead of FALSE.
Let me know what are your thoughts on this.

On Thu, Jun 16, 2016 at 10:41 AM, Iuliu Rus <iuliur at google.com<mailto:iuliur at google.com>> wrote:
Guys, am i OK continuing with the patch on the current code base or do you want me to wait until you pull in some more changes?

On Wed, Jun 15, 2016 at 8:37 AM, Thomas Freeman <thomas.freeman at hgst.com<mailto:thomas.freeman at hgst.com>> wrote:
Ray,
It appears that the latest patch file from Iuliu is applied to revision 137. I don’t see Suman’s changes in that revision.

As an example, the use of StorPortRequestTimer is not in nvmeStat.c.

I thought there were some newer revisions than 137, but 137 is the latest I’m able to download.
137 is also the revision that appears when I go to https://svn.openfabrics.org/svnrepo/nvmewin/

SVN is giving me some troubles, so I can’t tell for sure if this is my environment or a server issue.

Tom Freeman
Software Engineer, Device Manager and Driver Development
Western Digital Corporation
e.  Thomas.freeman at hgst.com<mailto:Thomas.freeman at hgst.com>
o.  +1-507-322-2311<tel:%2B1-507-322-2311>

[cid:image003.jpg at 01D1D1F7.245A73D0]

From: nvmewin [mailto:nvmewin-bounces at lists.openfabrics.org<mailto:nvmewin-bounces at lists.openfabrics.org>] On Behalf Of Robles, Raymond C
Sent: Friday, June 10, 2016 12:23 PM
To: Iuliu Rus <iuliur at google.com<mailto:iuliur at google.com>>; suman.p at samsung.com<mailto:suman.p at samsung.com>
Cc: nvmewin <nvmewin at lists.openfabrics.org<mailto:nvmewin at lists.openfabrics.org>>

Subject: Re: [nvmewin] review comments for patch from Google

Hi Iuliu,

If you send out the updated patch with the protection in place for both list entries and doorbells, I can run it on an Intel NVMe SSD (P3700) and see if there is any performance impact (up or down).

Thank you…
Ray

From: Iuliu Rus [mailto:iuliur at google.com]
Sent: Friday, June 10, 2016 10:17 AM
To: suman.p at samsung.com<mailto:suman.p at samsung.com>
Cc: Robles, Raymond C <raymond.c.robles at intel.com<mailto:raymond.c.robles at intel.com>>; Judy Brock <judy.brock at samsung.com<mailto:judy.brock at samsung.com>>; nvmewin <nvmewin at lists.openfabrics.org<mailto:nvmewin at lists.openfabrics.org>>
Subject: Re: RE: review comments for patch from Google

we are running this in a virtual machine, and we do see a perf difference with concurrent channels. We did not observe any performance drop with synchronized access to the list entry.

On Fri, Jun 10, 2016 at 7:15 AM, SUMAN PRAKASH B <suman.p at samsung.com<mailto:suman.p at samsung.com>> wrote:

Hi Iuliu,



As you have the implementation in place, can you let us know if there is any performance improvement when STOR_PERF_CONCURRENT_CHANNELS is set in case of #core and #queues not matching.

Also, if there is any drop in performance if the list entry and doorbell is protected after setting STOR_PERF_CONCURRENT_CHANNELS.



Perhaps a bit off topic:

Even in case when #cores and #queues are same and when STOR_PERF_CONCURRENT_CHANNELS is set, we did not observe any performance gain. Maybe we are hitting the max performance from device even without setting STOR_PERF_CONCURRENT_CHANNELS. Can you please let us know your observation?



Thanks,

Suman



------- Original Message -------

Sender : Robles, Raymond C<raymond.c.robles at intel.com<mailto:raymond.c.robles at intel.com>>

Date : Jun 10, 2016 08:30 (GMT+05:30)

Title : RE: review comments for patch from Google


Hi Judy,

Thanks for the additional info. I agree with the assessment. My statement was directed at the general direction of the solution… and the fact that I think option 1 is not as robust as option 2.

Thank you…
Ray

From: Judy Brock [mailto:judy.brock at samsung.com<mailto:judy.brock at samsung.com>]
Sent: Thursday, June 09, 2016 5:14 PM
To: Robles, Raymond C <raymond.c.robles at intel.com<mailto:raymond.c.robles at intel.com>>; Iuliu Rus <iuliur at google.com<mailto:iuliur at google.com>>; suman.p at samsung.com<mailto:suman.p at samsung.com>
Cc: nvmewin at lists.openfabrics.org<mailto:nvmewin at lists.openfabrics.org>
Subject: RE: review comments for patch from Google

Hi Ray et al,
[Suman wrote] >> Protect the listentry and doorbell before access/update
                             >>Do not set STOR_PERF_CONCURRENT_CHANNELS when number of cores and queues are not same.

Ray wrote] >>In the case Suman points out, concurrent channels should still be enabled even if the number of cores and queues do not match. This is especially true for large core count systems (>128 logical cpu cores) but devices may only support 32 queues or less

I think Suman was saying, we have two options:

1.       either don’t enable it at all if # cores != #queues or

2.       protect both the list entries and doorbell writes before any accesses/updates if #cores != #queues.

So we will need to check to see if we need to use locks or not in the performance path based on whether #cores and # queues DO match or not if we want to enable concurrent channels no matter what.   It’s probably better than option 1) above if this is a configuration that can come up frequently.

Thanks,
Judy


From: nvmewin [mailto:nvmewin-bounces at lists.openfabrics.org] On Behalf Of Robles, Raymond C
Sent: Thursday, June 09, 2016 2:32 PM
To: Iuliu Rus; suman.p at samsung.com<mailto:suman.p at samsung.com>
Cc: nvmewin at lists.openfabrics.org<mailto:nvmewin at lists.openfabrics.org>
Subject: Re: [nvmewin] review comments for patch from Google

Hi Iuliu/Suman,

I’m of the opinion that any solution provided should be as robust as possible. In the case Suman points out, concurrent channels should still be enabled even if the number of cores and queues do not match. This is especially true for large core count systems (>128 logical cpu cores) but devices may only support 32 queues or less.

Thank you…
Ray

From: Iuliu Rus [mailto:iuliur at google.com]<mailto:[mailto:iuliur at google.com]>
Sent: Thursday, June 09, 2016 2:09 PM
To: suman.p at samsung.com<mailto:suman.p at samsung.com>
Cc: Robles, Raymond C <raymond.c.robles at intel.com<mailto:raymond.c.robles at intel.com>>; nvmewin at lists.openfabrics.org<mailto:nvmewin at lists.openfabrics.org>
Subject: Re: review comments for patch from Google

Which one do you prefer? Our google driver has the synchronization in place already for a different reason. Or, I can follow your second suggestion.

On Thu, Jun 9, 2016 at 7:39 AM, SUMAN PRAKASH B <suman.p at samsung.com<mailto:suman.p at samsung.com>> wrote:

Hi Iuliu,



Please find my review comments below:



1. If the number of Cores and Queues supported by device are not same, then setting STOR_PERF_CONCURRENT_CHANNELS will corrupt the submission queue. For example, if device has 4 queues and connected to target PC which has 8 logical processors, and if STOR_PERF_CONCURRENT_CHANNELS is set, all the 8 logical processors will get startIo calls concurrently. As per OFA driver NUMA design, the IO Queue 1 will be shared by core 0 and core 4. There is possibility that core 0 and core 4 will get startio() calls concurrently and will access/update the listenty and queue 1 doorbell register at same time, which will lead to listentry and doorbell register corruption.
This problem can be address by following ways:
a. Protect the listentry and doorbell before access/update.
b. Do not set STOR_PERF_CONCURRENT_CHANNELS when number of cores and queues are not same.



2. We can use pRMT->NumActiveCores which is updated in NVMeEnumNumaCores() instead of using KeQueryActiveProcessorCountEx/KeQueryActiveProcessorCount.



Please let us know your opinion.



Thanks,
Suman



------- Original Message -------

Sender : Robles, Raymond C<raymond.c.robles at intel.com<mailto:raymond.c.robles at intel.com>>

Date : Jun 09, 2016 03:56 (GMT+05:30)

Title : Re: [nvmewin] Happy New Year... and status update


Thank you Iuliu!

Reviewing companies, please try to target the review completion for 2 weeks from today (6/22/16).

...

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