[ovs-dev] [PATCH 1/2] netdev-dpdk: Fix mempool creation with large MTU.

Fischetti, Antonio antonio.fischetti at intel.com
Tue Oct 31 13:37:59 UTC 2017


LGTM

Acked-by: Antonio Fischetti <antonio.fischetti at intel.com>


> -----Original Message-----
> From: Ilya Maximets [mailto:i.maximets at samsung.com]
> Sent: Tuesday, October 31, 2017 11:35 AM
> To: ovs-dev at openvswitch.org
> Cc: Heetae Ahn <heetae82.ahn at samsung.com>; Fischetti, Antonio
> <antonio.fischetti at intel.com>; Loftus, Ciara <ciara.loftus at intel.com>;
> Kavanagh, Mark B <mark.b.kavanagh at intel.com>; Stokes, Ian
> <ian.stokes at intel.com>; Wojciechowicz, RobertX
> <robertx.wojciechowicz at intel.com>; Ilya Maximets <i.maximets at samsung.com>
> Subject: [PATCH 1/2] netdev-dpdk: Fix mempool creation with large MTU.
> 
> Currently mempool name size limited to 25 characters by
> RTE_MEMPOOL_NAMESIZE. netdev-dpdk tries to create mempool with the
> following name pattern: "ovs_%{hash}_%{socket}_%{mtu}_%{n_mbuf}".
> 
> We have 3 chars for "ovs" + 4 chars for delimiters + 8 chars for
> hash (because it's the 32 bit integer printed in hex) + 1 char for
> socket_id (mostly 1, but it could be 2 on some systems; larger?) = 16.
> 
> Only 25 - 16 = 9 characters remains for mtu + n_mbufs.
> Minimum usual value for mtu is 1500 --> 2030 (4 chars) after
> dpdk_buf_size conversion and the minimum value for n_mbufs is 16384
> (5 chars). So, all the 9 characters are used.
> 
> If we'll try to create port with mtu = 9500, mempool creation will
> fail, because FRAME_LEN_TO_MTU(dpdk_buf_size(9500)) = 10222 (5 chars)
> and this value will overflow the RTE_MEMPOOL_NAMESIZE limit.
> 
> Same issue will happen if we'll try to create port with big enough
> number of queues or will try to create big enough number of PMD
> threads (number of tx queues will enlarge the mempool requirements).
> 
> Fix that by removing the delimiters. To keep the readability (at least
> partial) of the mempool names exact field sizes with zero padding
> are used.
> 
> Following limits should be suitable for now:
>  - Hash length: 8 chars (uint32_t in hex)
>  - Socket ID  : 2 chars (For systems with up to 10 sockets)
>  - MTU        : 5 chars (MTU (10^5 - 1) should be enough for now)
>  - n_mbufs    : 7 chars (Up to 10^7 of mbufs)
> 
>    Total      : 22 + 3 (for "ovs") = 25
> 
> CC: Antonio Fischetti <antonio.fischetti at intel.com>
> CC: Robert Wojciechowicz <robertx.wojciechowicz at intel.com>
> Fixes: f06546a51dd8 ("Fix mempool names to reflect socket id.")
> Fixes: d555d9bded5f ("netdev-dpdk: Create separate memory pool for each port.")
> Signed-off-by: Ilya Maximets <i.maximets at samsung.com>
> ---
>  lib/netdev-dpdk.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/lib/netdev-dpdk.c b/lib/netdev-dpdk.c
> index 0b40966..4ec536d 100644
> --- a/lib/netdev-dpdk.c
> +++ b/lib/netdev-dpdk.c
> @@ -500,7 +500,8 @@ dpdk_mp_create(struct netdev_dpdk *dev, int mtu)
>      do {
>          /* Full DPDK memory pool name must be unique and cannot be
>           * longer than RTE_MEMPOOL_NAMESIZE. */
> -        int ret = snprintf(mp_name, RTE_MEMPOOL_NAMESIZE, "ovs_%x_%d_%d_%u",
> +        int ret = snprintf(mp_name, RTE_MEMPOOL_NAMESIZE,
> +                           "ovs%08x%02d%05d%07u",
>                             hash, socket_id, mtu, n_mbufs);
>          if (ret < 0 || ret >= RTE_MEMPOOL_NAMESIZE) {
>              VLOG_DBG("snprintf returned %d. "
> --
> 2.7.4



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