Re: [PATCH v1 02/18] xprtrdma: Bound the inline threshold values

Anna Schumaker
2016-04-12T18:04:38Z

On 04/11/2016 04:10 PM, Chuck Lever wrote:
> Currently the sysctls that allow setting the inline threshold allow
> any value to be set.
>
> Small values only make the transport run slower. The default 1KB
> setting is as low as is reasonable. And the logic that decides how
> to divide a Send buffer buffer between RPC-over-RDMA header and RPC
^^^^^^^^^^^^^
I'm guessing you don't mean a buffer of buffers? :)

> message assumes (but does not check) that the lower bound is not
> crazy (say, 57 bytes).
>
> Send and receive buffers share a page with some control information.
> Values larger than about 3KB can't be supported, currently.
>
> Signed-off-by: Chuck Lever <chuck.lever-QHcLZuEGTsvQT0dZR+AlfA@public.gmane.org>
> ---
> include/linux/sunrpc/xprtrdma.h | 4 +++-
> net/sunrpc/xprtrdma/transport.c | 6 ++++++
> 2 files changed, 9 insertions(+), 1 deletion(-)
>
> diff --git a/include/linux/sunrpc/xprtrdma.h b/include/linux/sunrpc/xprtrdma.h
> index 767190b..39267dc 100644
> --- a/include/linux/sunrpc/xprtrdma.h
> +++ b/include/linux/sunrpc/xprtrdma.h
> @@ -52,7 +52,9 @@
> #define RPCRDMA_DEF_SLOT_TABLE (128U)
> #define RPCRDMA_MAX_SLOT_TABLE (256U)
>
> -#define RPCRDMA_DEF_INLINE (1024) /* default inline max */
> +#define RPCRDMA_MIN_INLINE (1024) /* min inline thresh */
> +#define RPCRDMA_DEF_INLINE (1024) /* default inline thresh */
> +#define RPCRDMA_MAX_INLINE (3068) /* max inline thresh */

It looks like RPCRDMA_DEF_INLINE is used to set xprt_rdma_max_inline_{read,write}. Are we keeping DEF_INLINE around so we can set these values separately from the minimum and maximum amounts?

Thanks,
Anna

>
> /* Memory registration strategies, by number.
> * This is part of a kernel / user space API. Do not remove. */
> diff --git a/net/sunrpc/xprtrdma/transport.c b/net/sunrpc/xprtrdma/transport.c
> index 9954342..16595ff 100644
> --- a/net/sunrpc/xprtrdma/transport.c
> +++ b/net/sunrpc/xprtrdma/transport.c
> @@ -73,6 +73,8 @@ static unsigned int xprt_rdma_memreg_strategy = RPCRDMA_FRMR;
>
> static unsigned int min_slot_table_size = RPCRDMA_MIN_SLOT_TABLE;
> static unsigned int max_slot_table_size = RPCRDMA_MAX_SLOT_TABLE;
> +static unsigned int min_inline_size = RPCRDMA_MIN_INLINE;
> +static unsigned int max_inline_size = RPCRDMA_MAX_INLINE;
> static unsigned int zero;
> static unsigned int max_padding = PAGE_SIZE;
> static unsigned int min_memreg = RPCRDMA_BOUNCEBUFFERS;
> @@ -96,6 +98,8 @@ static struct ctl_table xr_tunables_table[] = {
> .maxlen = sizeof(unsigned int),
> .mode = 0644,
> .proc_handler = proc_dointvec,
> + .extra1 = &min_inline_size,
> + .extra2 = &max_inline_size,
> },
> {
> .procname = "rdma_max_inline_write",
> @@ -103,6 +107,8 @@ static struct ctl_table xr_tunables_table[] = {
> .maxlen = sizeof(unsigned int),
> .mode = 0644,
> .proc_handler = proc_dointvec,
> + .extra1 = &min_inline_size,
> + .extra2 = &max_inline_size,
> },
> {
> .procname = "rdma_inline_write_padding",
>
> --
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