Re: [PATCH v2 2/9] platform/surface: aggregator: Add control packet allocation caching

Hans de Goede
2020-12-15T13:45:13Z

Hi,

On 12/3/20 10:26 PM, Maximilian Luz wrote:
> Surface Serial Hub communication is, in its core, packet based. Each
> sequenced packet requires to be acknowledged, via an ACK-type control
> packet. In case invalid data has been received by the driver, a NAK-type
> (not-acknowledge/negative acknowledge) control packet is sent,
> triggering retransmission.
>
> Control packets are therefore a core communication primitive and used
> frequently enough (with every sequenced packet transmission sent by the
> embedded controller, including events and request responses) that it may
> warrant caching their allocations to reduce possible memory
> fragmentation.
>
> Signed-off-by: Maximilian Luz <luzmaximilian@gmail.com>

Thanks, patch looks good to me:

Reviewed-by: Hans de Goede <hdegoede@redhat.com>

Regards,

Hans

> ---
> drivers/platform/surface/aggregator/core.c | 27 ++++++++++-
> .../surface/aggregator/ssh_packet_layer.c | 47 +++++++++++++++----
> .../surface/aggregator/ssh_packet_layer.h | 3 ++
> 3 files changed, 67 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/platform/surface/aggregator/core.c b/drivers/platform/surface/aggregator/core.c
> index ec6c7f40ad36..77bc4c87541b 100644
> --- a/drivers/platform/surface/aggregator/core.c
> +++ b/drivers/platform/surface/aggregator/core.c
> @@ -774,7 +774,32 @@ static struct serdev_device_driver ssam_serial_hub = {
> .probe_type = PROBE_PREFER_ASYNCHRONOUS,
> },
> };
> -module_serdev_device_driver(ssam_serial_hub);
> +
> +
> +/* -- Module setup. --------------------------------------------------------- */
> +
> +static int __init ssam_core_init(void)
> +{
> + int status;
> +
> + status = ssh_ctrl_packet_cache_init();
> + if (status)
> + return status;
> +
> + status = serdev_device_driver_register(&ssam_serial_hub);
> + if (status)
> + ssh_ctrl_packet_cache_destroy();
> +
> + return status;
> +}
> +module_init(ssam_core_init);
> +
> +static void __exit ssam_core_exit(void)
> +{
> + serdev_device_driver_unregister(&ssam_serial_hub);
> + ssh_ctrl_packet_cache_destroy();
> +}
> +module_exit(ssam_core_exit);
>
> MODULE_AUTHOR("Maximilian Luz <luzmaximilian@gmail.com>");
> MODULE_DESCRIPTION("Subsystem and Surface Serial Hub driver for Surface System Aggregator Module");
> diff --git a/drivers/platform/surface/aggregator/ssh_packet_layer.c b/drivers/platform/surface/aggregator/ssh_packet_layer.c
> index 237d28c90e4b..8bc19837cde0 100644
> --- a/drivers/platform/surface/aggregator/ssh_packet_layer.c
> +++ b/drivers/platform/surface/aggregator/ssh_packet_layer.c
> @@ -302,24 +302,53 @@ void ssh_packet_init(struct ssh_packet *packet, unsigned long type,
> packet->ops = ops;
> }
>
> +static struct kmem_cache *ssh_ctrl_packet_cache;
> +
> +/**
> + * ssh_ctrl_packet_cache_init() - Initialize the control packet cache.
> + */
> +int ssh_ctrl_packet_cache_init(void)
> +{
> + const unsigned int size = sizeof(struct ssh_packet) + SSH_MSG_LEN_CTRL;
> + const unsigned int align = __alignof__(struct ssh_packet);
> + struct kmem_cache *cache;
> +
> + cache = kmem_cache_create("ssam_ctrl_packet", size, align, 0, NULL);
> + if (!cache)
> + return -ENOMEM;
> +
> + ssh_ctrl_packet_cache = cache;
> + return 0;
> +}
> +
> +/**
> + * ssh_ctrl_packet_cache_destroy() - Deinitialize the control packet cache.
> + */
> +void ssh_ctrl_packet_cache_destroy(void)
> +{
> + kmem_cache_destroy(ssh_ctrl_packet_cache);
> + ssh_ctrl_packet_cache = NULL;
> +}
> +
> /**
> - * ssh_ctrl_packet_alloc() - Allocate control packet.
> + * ssh_ctrl_packet_alloc() - Allocate packet from control packet cache.
> * @packet: Where the pointer to the newly allocated packet should be stored.
> * @buffer: The buffer corresponding to this packet.
> * @flags: Flags used for allocation.
> *
> - * Allocates a packet and corresponding transport buffer. Sets the packet's
> - * buffer reference to the allocated buffer. The packet must be freed via
> - * ssh_ctrl_packet_free(), which will also free the corresponding buffer. The
> - * corresponding buffer must not be freed separately. Intended to be used with
> - * %ssh_ptl_ctrl_packet_ops as packet operations.
> + * Allocates a packet and corresponding transport buffer from the control
> + * packet cache. Sets the packet's buffer reference to the allocated buffer.
> + * The packet must be freed via ssh_ctrl_packet_free(), which will also free
> + * the corresponding buffer. The corresponding buffer must not be freed
> + * separately. Intended to be used with %ssh_ptl_ctrl_packet_ops as packet
> + * operations.
> *
> * Return: Returns zero on success, %-ENOMEM if the allocation failed.
> */
> static int ssh_ctrl_packet_alloc(struct ssh_packet **packet,
> struct ssam_span *buffer, gfp_t flags)
> {
> - *packet = kzalloc(sizeof(**packet) + SSH_MSG_LEN_CTRL, flags);
> + *packet = kmem_cache_alloc(ssh_ctrl_packet_cache, flags);
> if (!*packet)
> return -ENOMEM;
>
> @@ -330,12 +359,12 @@ static int ssh_ctrl_packet_alloc(struct ssh_packet **packet,
> }
>
> /**
> - * ssh_ctrl_packet_free() - Free control packet.
> + * ssh_ctrl_packet_free() - Free packet allocated from control packet cache.
> * @p: The packet to free.
> */
> static void ssh_ctrl_packet_free(struct ssh_packet *p)
> {
> - kfree(p);
> + kmem_cache_free(ssh_ctrl_packet_cache, p);
> }
>
> static const struct ssh_packet_ops ssh_ptl_ctrl_packet_ops = {
> diff --git a/drivers/platform/surface/aggregator/ssh_packet_layer.h b/drivers/platform/surface/aggregator/ssh_packet_layer.h
> index 058f111292ca..e8757d03f279 100644
> --- a/drivers/platform/surface/aggregator/ssh_packet_layer.h
> +++ b/drivers/platform/surface/aggregator/ssh_packet_layer.h
> @@ -184,4 +184,7 @@ static inline void ssh_ptl_tx_wakeup_transfer(struct ssh_ptl *ptl)
> void ssh_packet_init(struct ssh_packet *packet, unsigned long type,
> u8 priority, const struct ssh_packet_ops *ops);
>
> +int ssh_ctrl_packet_cache_init(void);
> +void ssh_ctrl_packet_cache_destroy(void);
> +
> #endif /* _SURFACE_AGGREGATOR_SSH_PACKET_LAYER_H */
> --
> 2.29.2
>