leandrof/linux
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

ibmvnic: Allow multiple ltbs in rxpool ltb_set

Browse Source 
Allow multiple LTBs in the rxpool's ltb_set. The first n-1 LTBs will all
be of the same size. The size of the last LTB in the set depends on the
number of buffers and buffer (mtu) size.

Having a set of LTBs per pool provides a couple of benefits.

First, with the current value of IBMVNIC_MAX_LTB_SIZE of 16MB, with an
MTU of 9000, we need a LTB (DMA buffer) of that size but the allocation
can fail in low memory conditions. With a set of LTBs per pool, we can
use several smaller (8MB) LTBs and hopefully have fewer allocation
failures. (See also comments in ibmvnic.h on the trade-off with smaller
LTBs)

Second since the kernel limits the size of the DMA buffer to 16MB (based
on MAX_ORDER), with a single DMA buffer per pool, the pool is also limited
to 16MB. This in turn limits the number of buffers per pool to 1763 when
MTU is 9000. With a set of LTBs per pool, we can have upto the max of 4096
buffers per pool even when MTU is 9000.

Suggested-by: Brian King <brking@linux.ibm.com>
Signed-off-by: Sukadev Bhattiprolu <sukadev@linux.ibm.com>
Signed-off-by: Dany Madden <drt@linux.ibm.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Sukadev Bhattiprolu 2022-04-13 13:10:25 -04:00 committed by Jakub Kicinski
parent d6b4585090
commit a75de82057
2 changed files with 177 additions and 20 deletions
drivers/net/ethernet/ibm
ibmvnic.cibmvnic.h

152
drivers/net/ethernet/ibm/ibmvnic.c
View File

@ -345,6 +345,14 @@ static void free_long_term_buff(struct ibmvnic_adapter *adapter,
ltb->map_id = 0;
}
/**
* free_ltb_set - free the given set of long term buffers (LTBS)
* @adapter: The ibmvnic adapter containing this ltb set
* @ltb_set: The ltb_set to be freed
*
* Free the set of LTBs in the given set.
*/
static void free_ltb_set(struct ibmvnic_adapter *adapter,
struct ibmvnic_ltb_set *ltb_set)
{
@ -358,26 +366,117 @@ static void free_ltb_set(struct ibmvnic_adapter *adapter,
ltb_set->num_ltbs = 0;
}
/**
* alloc_ltb_set() - Allocate a set of long term buffers (LTBs)
*
* @adapter: ibmvnic adapter associated to the LTB
* @ltb_set: container object for the set of LTBs
* @num_buffs: Number of buffers in the LTB
* @buff_size: Size of each buffer in the LTB
*
* Allocate a set of LTBs to accommodate @num_buffs buffers of @buff_size
* each. We currently cap size each LTB to IBMVNIC_ONE_LTB_SIZE. If the
* new set of LTBs have fewer LTBs than the old set, free the excess LTBs.
* If new set needs more than in old set, allocate the remaining ones.
* Try and reuse as many LTBs as possible and avoid reallocation.
*
* Any changes to this allocation strategy must be reflected in
* map_rxpool_buff_to_ltb() and map_txpool_buff_to_ltb().
*/
static int alloc_ltb_set(struct ibmvnic_adapter *adapter,
struct ibmvnic_ltb_set *ltb_set, int num_buffs,
int buff_size)
{
struct ibmvnic_long_term_buff *ltb;
int ltb_size;
int size;
struct device *dev = &adapter->vdev->dev;
struct ibmvnic_ltb_set old_set;
struct ibmvnic_ltb_set new_set;
int rem_size;
int tot_size; /* size of all ltbs */
int ltb_size; /* size of one ltb */
int nltbs;
int rc;
int n;
int i;
size = sizeof(struct ibmvnic_long_term_buff);
dev_dbg(dev, "%s() num_buffs %d, buff_size %d\n", __func__, num_buffs,
buff_size);
ltb_set->ltbs = kmalloc(size, GFP_KERNEL);
if (!ltb_set->ltbs)
return -ENOMEM;
ltb_size = rounddown(IBMVNIC_ONE_LTB_SIZE, buff_size);
tot_size = num_buffs * buff_size;
ltb_set->num_ltbs = 1;
ltb = &ltb_set->ltbs[0];
if (ltb_size > tot_size)
ltb_size = tot_size;
ltb_size = num_buffs * buff_size;
nltbs = tot_size / ltb_size;
if (tot_size % ltb_size)
nltbs++;
return alloc_long_term_buff(adapter, ltb, ltb_size);
old_set = *ltb_set;
if (old_set.num_ltbs == nltbs) {
new_set = old_set;
} else {
int tmp = nltbs * sizeof(struct ibmvnic_long_term_buff);
new_set.ltbs = kzalloc(tmp, GFP_KERNEL);
if (!new_set.ltbs)
return -ENOMEM;
new_set.num_ltbs = nltbs;
/* Free any excess ltbs in old set */
for (i = new_set.num_ltbs; i < old_set.num_ltbs; i++)
free_long_term_buff(adapter, &old_set.ltbs[i]);
/* Copy remaining ltbs to new set. All LTBs except the
* last one are of the same size. alloc_long_term_buff()
* will realloc if the size changes.
*/
n = min(old_set.num_ltbs, new_set.num_ltbs);
for (i = 0; i < n; i++)
new_set.ltbs[i] = old_set.ltbs[i];
/* Any additional ltbs in new set will have NULL ltbs for
* now and will be allocated in alloc_long_term_buff().
*/
/* We no longer need the old_set so free it. Note that we
* may have reused some ltbs from old set and freed excess
* ltbs above. So we only need to free the container now
* not the LTBs themselves. (i.e. dont free_ltb_set()!)
*/
kfree(old_set.ltbs);
old_set.ltbs = NULL;
old_set.num_ltbs = 0;
/* Install the new set. If allocations fail below, we will
* retry later and know what size LTBs we need.
*/
*ltb_set = new_set;
}
i = 0;
rem_size = tot_size;
while (rem_size) {
if (ltb_size > rem_size)
ltb_size = rem_size;
rem_size -= ltb_size;
rc = alloc_long_term_buff(adapter, &new_set.ltbs[i], ltb_size);
if (rc)
goto out;
i++;
}
WARN_ON(i != new_set.num_ltbs);
return 0;
out:
/* We may have allocated one/more LTBs before failing and we
* want to try and reuse on next reset. So don't free ltb set.
*/
return rc;
}
/**
@ -388,14 +487,30 @@ static int alloc_ltb_set(struct ibmvnic_adapter *adapter,
* @offset: (Output) offset of buffer in the LTB from @ltbp
*
* Map the given buffer identified by [rxpool, bufidx] to an LTB in the
* pool and its corresponding offset.
* pool and its corresponding offset. Assume for now that each LTB is of
* different size but could possibly be optimized based on the allocation
* strategy in alloc_ltb_set().
*/
static void map_rxpool_buf_to_ltb(struct ibmvnic_rx_pool *rxpool,
unsigned int bufidx,
struct ibmvnic_long_term_buff **ltbp,
unsigned int *offset)
{
*ltbp = &rxpool->ltb_set.ltbs[0];
struct ibmvnic_long_term_buff *ltb;
int nbufs; /* # of buffers in one ltb */
int i;
WARN_ON(bufidx >= rxpool->size);
for (i = 0; i < rxpool->ltb_set.num_ltbs; i++) {
ltb = &rxpool->ltb_set.ltbs[i];
nbufs = ltb->size / rxpool->buff_size;
if (bufidx < nbufs)
break;
bufidx -= nbufs;
}
*ltbp = ltb;
*offset = bufidx * rxpool->buff_size;
}
@ -798,8 +913,9 @@ update_ltb:
dev_dbg(dev, "Updating LTB for rx pool %d [%d, %d]\n",
i, rx_pool->size, rx_pool->buff_size);
if (alloc_ltb_set(adapter, &rx_pool->ltb_set,
rx_pool->size, rx_pool->buff_size))
rc = alloc_ltb_set(adapter, &rx_pool->ltb_set,
rx_pool->size, rx_pool->buff_size);
if (rc)
goto out;
for (j = 0; j < rx_pool->size; ++j) {
@ -4106,16 +4222,16 @@ static void send_request_cap(struct ibmvnic_adapter *adapter, int retry)
adapter->desired.rx_entries =
adapter->max_rx_add_entries_per_subcrq;
max_entries = IBMVNIC_MAX_LTB_SIZE /
max_entries = IBMVNIC_LTB_SET_SIZE /
(adapter->req_mtu + IBMVNIC_BUFFER_HLEN);
if ((adapter->req_mtu + IBMVNIC_BUFFER_HLEN) *
adapter->desired.tx_entries > IBMVNIC_MAX_LTB_SIZE) {
adapter->desired.tx_entries > IBMVNIC_LTB_SET_SIZE) {
adapter->desired.tx_entries = max_entries;
}
if ((adapter->req_mtu + IBMVNIC_BUFFER_HLEN) *
adapter->desired.rx_entries > IBMVNIC_MAX_LTB_SIZE) {
adapter->desired.rx_entries > IBMVNIC_LTB_SET_SIZE) {
adapter->desired.rx_entries = max_entries;
}

45
drivers/net/ethernet/ibm/ibmvnic.h
View File

@ -36,9 +36,50 @@
#define IBMVNIC_TSO_BUFS 64
#define IBMVNIC_TSO_POOL_MASK 0x80000000
#define IBMVNIC_MAX_LTB_SIZE ((1 << (MAX_ORDER - 1)) * PAGE_SIZE)
#define IBMVNIC_BUFFER_HLEN 500
/* A VNIC adapter has set of Rx and Tx pools (aka queues). Each Rx/Tx pool
* has a set of buffers. The size of each buffer is determined by the MTU.
*
* Each Rx/Tx pool is also associated with a DMA region that is shared
* with the "hardware" (VIOS) and used to send/receive packets. The DMA
* region is also referred to as a Long Term Buffer or LTB.
*
* The size of the DMA region required for an Rx/Tx pool depends on the
* number and size (MTU) of the buffers in the pool. At the max levels
* of 4096 jumbo frames (MTU=9000) we will need about 9K*4K = 36MB plus
* some padding.
*
* But the size of a single DMA region is limited by MAX_ORDER in the
* kernel (about 16MB currently). To support say 4K Jumbo frames, we
* use a set of LTBs (struct ltb_set) per pool.
*
* IBMVNIC_ONE_LTB_MAX - max size of each LTB supported by kernel
* IBMVNIC_ONE_LTB_SIZE - current max size of each LTB in an ltb_set
* (must be <= IBMVNIC_ONE_LTB_MAX)
* IBMVNIC_LTB_SET_SIZE - current size of all LTBs in an ltb_set
*
* Each VNIC can have upto 16 Rx, 16 Tx and 16 TSO pools. The TSO pools
* are of fixed length (IBMVNIC_TSO_BUF_SZ * IBMVNIC_TSO_BUFS) of 4MB.
*
* The Rx and Tx pools can have upto 4096 buffers. The max size of these
* buffers is about 9588 (for jumbo frames, including IBMVNIC_BUFFER_HLEN).
* So, setting the IBMVNIC_LTB_SET_SIZE for a pool to 4096 * 9588 ~= 38MB.
*
* There is a trade-off in setting IBMVNIC_ONE_LTB_SIZE. If it is large,
* the allocation of the LTB can fail when system is low in memory. If
* its too small, we would need several mappings for each of the Rx/
* Tx/TSO pools but there is a limit of 255 mappings per vnic in the
* VNIC protocol.
*
* So setting IBMVNIC_ONE_LTB_SIZE to 8MB. With IBMVNIC_LTB_SET_SIZE set
* to 38MB, we will need 5 LTBs per Rx and Tx pool and 1 LTB per TSO
* pool for the 4MB. Thus the 16 Rx and Tx queues require 32 * 5 = 160
* plus 16 for the TSO pools for a total of 176 LTB mappings per VNIC.
*/
#define IBMVNIC_ONE_LTB_MAX ((u32)((1 << (MAX_ORDER - 1)) * PAGE_SIZE))
#define IBMVNIC_ONE_LTB_SIZE min((u32)(8 << 20), IBMVNIC_ONE_LTB_MAX)
#define IBMVNIC_LTB_SET_SIZE (38 << 20)
#define IBMVNIC_BUFFER_HLEN 500
#define IBMVNIC_RESET_DELAY 100
static const char ibmvnic_priv_flags[][ETH_GSTRING_LEN] = {