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Message-ID: <9a17268d4046f99b30f3620079b5749a9ddc5cd9.camel@linux.ibm.com>
Date: Wed, 03 Apr 2024 19:20:30 +0200
From: Gerd Bayer <gbayer@...ux.ibm.com>
To: Wen Gu <guwen@...ux.alibaba.com>, wintera@...ux.ibm.com,
twinkler@...ux.ibm.com, hca@...ux.ibm.com, gor@...ux.ibm.com,
agordeev@...ux.ibm.com, davem@...emloft.net, edumazet@...gle.com,
kuba@...nel.org, pabeni@...hat.com, wenjia@...ux.ibm.com,
jaka@...ux.ibm.com
Cc: borntraeger@...ux.ibm.com, svens@...ux.ibm.com, alibuda@...ux.alibaba.com,
tonylu@...ux.alibaba.com, linux-kernel@...r.kernel.org,
linux-s390@...r.kernel.org, netdev@...r.kernel.org
Subject: Re: [RFC PATCH net-next v5 05/11] net/smc: implement DMB-related
operations of loopback-ism
On Sun, 2024-03-24 at 21:55 +0800, Wen Gu wrote:
When I instrumented this to see, why I still see tons of my other
temporary instrumentation messages from the "ism" driver, I found that
in my setup loopback-ism is used rather infrequently.
I suspect this is due to how the SMC proposals are constructed in
net/smc/af_smc.c and net/smc/smc_pnet.c - and later evaluated in
smc_check_ism_v2_match() - where there is a first-come-first-serve
selection.
I wonder if one should change that to favour loopback-ism over "real"
ISM devices - and how this could be achieved elegantly.
Just some food for thought... Probably little you can do on x86.
Thanks,
Gerd
> +static int smc_lo_register_dmb(struct smcd_dev *smcd, struct
> smcd_dmb *dmb,
> + void *client_priv)
> +{
> + struct smc_lo_dmb_node *dmb_node, *tmp_node;
> + struct smc_lo_dev *ldev = smcd->priv;
> + int sba_idx, rc;
> +
> + /* check space for new dmb */
> + for_each_clear_bit(sba_idx, ldev->sba_idx_mask,
> SMC_LO_MAX_DMBS) {
> + if (!test_and_set_bit(sba_idx, ldev->sba_idx_mask))
> + break;
> + }
> + if (sba_idx == SMC_LO_MAX_DMBS)
> + return -ENOSPC;
> +
> + dmb_node = kzalloc(sizeof(*dmb_node), GFP_KERNEL);
> + if (!dmb_node) {
> + rc = -ENOMEM;
> + goto err_bit;
> + }
> +
> + dmb_node->sba_idx = sba_idx;
> + dmb_node->len = dmb->dmb_len;
> + dmb_node->cpu_addr = kzalloc(dmb_node->len, GFP_KERNEL |
> + __GFP_NOWARN | __GFP_NORETRY |
> + __GFP_NOMEMALLOC);
> + if (!dmb_node->cpu_addr) {
> + rc = -ENOMEM;
> + goto err_node;
> + }
> + dmb_node->dma_addr = SMC_DMA_ADDR_INVALID;
> +
> +again:
> + /* add new dmb into hash table */
> + get_random_bytes(&dmb_node->token, sizeof(dmb_node->token));
> + write_lock_bh(&ldev->dmb_ht_lock);
> + hash_for_each_possible(ldev->dmb_ht, tmp_node, list,
> dmb_node->token) {
> + if (tmp_node->token == dmb_node->token) {
> + write_unlock_bh(&ldev->dmb_ht_lock);
> + goto again;
> + }
> + }
> + hash_add(ldev->dmb_ht, &dmb_node->list, dmb_node->token);
> + write_unlock_bh(&ldev->dmb_ht_lock);
> +
> + dmb->sba_idx = dmb_node->sba_idx;
> + dmb->dmb_tok = dmb_node->token;
> + dmb->cpu_addr = dmb_node->cpu_addr;
> + dmb->dma_addr = dmb_node->dma_addr;
> + dmb->dmb_len = dmb_node->len;
> +
> + return 0;
> +
> +err_node:
> + kfree(dmb_node);
> +err_bit:
> + clear_bit(sba_idx, ldev->sba_idx_mask);
> + return rc;
> +}
> +
> +static int smc_lo_unregister_dmb(struct smcd_dev *smcd, struct
> smcd_dmb *dmb)
> +{
> + struct smc_lo_dmb_node *dmb_node = NULL, *tmp_node;
> + struct smc_lo_dev *ldev = smcd->priv;
> +
> + /* remove dmb from hash table */
> + write_lock_bh(&ldev->dmb_ht_lock);
> + hash_for_each_possible(ldev->dmb_ht, tmp_node, list, dmb-
> >dmb_tok) {
> + if (tmp_node->token == dmb->dmb_tok) {
> + dmb_node = tmp_node;
> + break;
> + }
> + }
> + if (!dmb_node) {
> + write_unlock_bh(&ldev->dmb_ht_lock);
> + return -EINVAL;
> + }
> + hash_del(&dmb_node->list);
> + write_unlock_bh(&ldev->dmb_ht_lock);
> +
> + clear_bit(dmb_node->sba_idx, ldev->sba_idx_mask);
> + kfree(dmb_node->cpu_addr);
> + kfree(dmb_node);
> +
> + return 0;
> +}
> +
> static int smc_lo_add_vlan_id(struct smcd_dev *smcd, u64 vlan_id)
> {
> return -EOPNOTSUPP;
> @@ -75,6 +164,38 @@ static int smc_lo_signal_event(struct smcd_dev
> *dev, struct smcd_gid *rgid,
> return 0;
> }
>
> +static int smc_lo_move_data(struct smcd_dev *smcd, u64 dmb_tok,
> + unsigned int idx, bool sf, unsigned int
> offset,
> + void *data, unsigned int size)
> +{
> + struct smc_lo_dmb_node *rmb_node = NULL, *tmp_node;
> + struct smc_lo_dev *ldev = smcd->priv;
> + struct smc_connection *conn;
> +
> + read_lock_bh(&ldev->dmb_ht_lock);
> + hash_for_each_possible(ldev->dmb_ht, tmp_node, list,
> dmb_tok) {
> + if (tmp_node->token == dmb_tok) {
> + rmb_node = tmp_node;
> + break;
> + }
> + }
> + if (!rmb_node) {
> + read_unlock_bh(&ldev->dmb_ht_lock);
> + return -EINVAL;
> + }
> + memcpy((char *)rmb_node->cpu_addr + offset, data, size);
> + read_unlock_bh(&ldev->dmb_ht_lock);
> +
> + if (sf) {
> + conn = smcd->conn[rmb_node->sba_idx];
> + if (conn && !conn->killed)
> + tasklet_schedule(&conn->rx_tsklet);
> + else
> + return -EPIPE;
> + }
> + return 0;
> +}
> +
> static int smc_lo_supports_v2(void)
> {
> return SMC_LO_V2_CAPABLE;
> @@ -101,14 +222,14 @@ static struct device *smc_lo_get_dev(struct
> smcd_dev *smcd)
>
> static const struct smcd_ops lo_ops = {
> .query_remote_gid = smc_lo_query_rgid,
> - .register_dmb = NULL,
> - .unregister_dmb = NULL,
> + .register_dmb = smc_lo_register_dmb,
> + .unregister_dmb = smc_lo_unregister_dmb,
> .add_vlan_id = smc_lo_add_vlan_id,
> .del_vlan_id = smc_lo_del_vlan_id,
> .set_vlan_required = smc_lo_set_vlan_required,
> .reset_vlan_required = smc_lo_reset_vlan_required,
> .signal_event = smc_lo_signal_event,
> - .move_data = NULL,
> + .move_data = smc_lo_move_data,
> .supports_v2 = smc_lo_supports_v2,
> .get_local_gid = smc_lo_get_local_gid,
> .get_chid = smc_lo_get_chid,
> @@ -173,6 +294,8 @@ static void smcd_lo_unregister_dev(struct
> smc_lo_dev *ldev)
> static int smc_lo_dev_init(struct smc_lo_dev *ldev)
> {
> smc_lo_generate_ids(ldev);
> + rwlock_init(&ldev->dmb_ht_lock);
> + hash_init(ldev->dmb_ht);
> return smcd_lo_register_dev(ldev);
> }
>
> diff --git a/net/smc/smc_loopback.h b/net/smc/smc_loopback.h
> index 11868e5ac732..6c4a390430f3 100644
> --- a/net/smc/smc_loopback.h
> +++ b/net/smc/smc_loopback.h
> @@ -20,13 +20,26 @@
>
> #if IS_ENABLED(CONFIG_SMC_LO)
> #define SMC_LO_MAX_DMBS 5000
> +#define SMC_LO_DMBS_HASH_BITS 12
> #define SMC_LO_RESERVED_CHID 0xFFFF
>
> +struct smc_lo_dmb_node {
> + struct hlist_node list;
> + u64 token;
> + u32 len;
> + u32 sba_idx;
> + void *cpu_addr;
> + dma_addr_t dma_addr;
> +};
> +
> struct smc_lo_dev {
> struct smcd_dev *smcd;
> struct device dev;
> u16 chid;
> struct smcd_gid local_gid;
> + rwlock_t dmb_ht_lock;
> + DECLARE_BITMAP(sba_idx_mask, SMC_LO_MAX_DMBS);
> + DECLARE_HASHTABLE(dmb_ht, SMC_LO_DMBS_HASH_BITS);
> };
> #endif
>
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