netdev - Re: [PATCH net-next 0/9] ibmvnic: Reuse ltb, rx, tx pools

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Message-ID: <19897bfd-e13e-a32a-fd14-b4f0f7e47db1@linux.vnet.ibm.com>
Date:   Tue, 31 Aug 2021 18:21:32 -0700
From:   Rick Lindsley <ricklind@...ux.vnet.ibm.com>
To:     Sukadev Bhattiprolu <sukadev@...ux.ibm.com>, netdev@...r.kernel.org
Cc:     Brian King <brking@...ux.ibm.com>, cforno12@...ux.ibm.com,
        Dany Madden <drt@...ux.ibm.com>,
        Rick Lindsley <ricklind@...ux.ibm.com>
Subject: Re: [PATCH net-next 0/9] ibmvnic: Reuse ltb, rx, tx pools

On 8/31/21 5:08 PM, Sukadev Bhattiprolu wrote:
> It can take a long time to free and reallocate rx and tx pools and long
> term buffer (LTB) during each reset of the VNIC. This is specially true
> when the partition (LPAR) is heavily loaded and going through a Logical
> Partition Migration (LPM). The long drawn reset causes the LPAR to lose
> connectivity for extended periods of time and results in "RMC connection"
> errors and the LPM failing.
> 
> What is worse is that during the LPM we could get a failover because
> of the lost connectivity. At that point, the vnic driver releases
> even the resources it has already allocated and starts over.
> 
> As long as the resources we have already allocated are valid/applicable,
> we might as well hold on to them while trying to allocate the remaining
> resources. This patch set attempts to reuse the resources previously
> allocated as long as they are valid. It seems to vastly improve the
> time taken for the vnic reset. We have also not seen any RMC connection
> issues during our testing with this patch set.
> 
> If the backing devices for a vnic adapter are not "matched" (see "pool
> parameters" in patches 8 and 9) it is possible that we will still free
> all the resources and allocate them. If that becomes a common problem,
> we have to address it separately.

We have spent a good amount of time going over this. Thans for all the work.

Reviewed-by:  Rick Lindsley <ricklind@...ux.vnet.ibm.com>