Re: [PATCH net-next 1/2] net/mlx5e: Batch NAPI RCU grace periods on channel close

[sashiko-bot@kernel.org]

> From: Carolina Jubran <cjubran@nvidia.com>
> 
> Channel close currently invokes synchronize_net() repeatedly while
> tearing down each channel. RQ, ICOSQ, TX SQ and NAPI teardown each
> require a grace period, causing the number of waits to scale with the
> number of channels. TX SQ teardown adds a wait for each traffic class,
> while XDP and QoS can add further calls.
> 
> Batch these waits across all channels. Split channel deactivate and
> close into pre_sync and post_sync phases. First clear the ENABLED state
> on all queues, then wait for a single grace period before continuing
> with the teardown.
> 
> Similarly, unlink all NAPI instances with
> __netif_napi_del_locked(), issue one synchronize_net() after all of
> them have been unlinked, and only then free the channels.
> 
> Keep the existing per object synchronize_net() calls for single queue
> paths.
> 
> 248 channels, rcu_normal=1, ip link set eth2 down:
> Before: 10.183s
> After:   0.715s (~14x faster)
> 
> Signed-off-by: Carolina Jubran <cjubran@nvidia.com>
> Signed-off-by: Tariq Toukan <tariqt@nvidia.com>

Sashiko has reviewed this patch and found no issues. It looks great!

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