On Fri, Jan 8, 2016 at 5:35 AM, <tim.gardner@xxxxxxxxxxxxx> wrote:
> From: Tim Gardner <tim.gardner@xxxxxxxxxxxxx>
>
> CC [M] drivers/dma/ioat/prep.o
> drivers/dma/ioat/prep.c: In function 'ioat_prep_pqxor':
> drivers/dma/ioat/prep.c:682:1: warning: the frame size of 1048 bytes is larger than 1024 bytes [-Wframe-larger-than=]
> }
> ^
> drivers/dma/ioat/prep.c: In function 'ioat_prep_pqxor_val':
> drivers/dma/ioat/prep.c:714:1: warning: the frame size of 1048 bytes is larger than 1024 bytes [-Wframe-larger-than=]
> }
>
> gcc version 5.3.1 20151219 (Ubuntu 5.3.1-4ubuntu1)
>
> Cc: Vinod Koul <vinod.koul@xxxxxxxxx>
> Cc: Dan Williams <dan.j.williams@xxxxxxxxx>
> Cc: Dave Jiang <dave.jiang@xxxxxxxxx>
> Cc: Prarit Bhargava <prarit@xxxxxxxxxx>
> Cc: Nicholas Mc Guire <der.herr@xxxxxxx>
> Cc: Jarkko Nikula <jarkko.nikula@xxxxxxxxxxxxxxx>
> Signed-off-by: Tim Gardner <tim.gardner@xxxxxxxxxxxxx>
> ---
>
> v2 - use per CPU static buffers instead of dynamically allocating memory.
>
> drivers/dma/ioat/prep.c | 33 +++++++++++++++++++++++++++++----
> 1 file changed, 29 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/dma/ioat/prep.c b/drivers/dma/ioat/prep.c
> index 6bb4a13..2c0768b 100644
> --- a/drivers/dma/ioat/prep.c
> +++ b/drivers/dma/ioat/prep.c
> @@ -21,6 +21,8 @@
> #include <linux/dmaengine.h>
> #include <linux/dma-mapping.h>
> #include <linux/prefetch.h>
> +#include <linux/percpu.h>
> +#include <linux/preempt.h>
> #include "../dmaengine.h"
> #include "registers.h"
> #include "hw.h"
> @@ -655,13 +657,25 @@ ioat_prep_pq_val(struct dma_chan *chan, dma_addr_t *pq, dma_addr_t *src,
> flags);
> }
>
> +/*
> + * The scf scratch buffer is too large for an automatic variable, and
> + * we don't want to take the performance hit for dynamic allocation.
> + * Therefore, define per CPU buffers and disable preemption while in use.
> + */
> +static DEFINE_PER_CPU(unsigned char [MAX_SCF], ioat_scf);
> +static inline unsigned char *ioat_assign_scratch_buffer(void)
> +{
> + return get_cpu_var(ioat_scf);
This get needs to be paired with a put_cpu_var().
> +}
> +
> struct dma_async_tx_descriptor *
> ioat_prep_pqxor(struct dma_chan *chan, dma_addr_t dst, dma_addr_t *src,
> unsigned int src_cnt, size_t len, unsigned long flags)
> {
> - unsigned char scf[MAX_SCF];
> + unsigned char *scf;
> dma_addr_t pq[2];
> struct ioatdma_chan *ioat_chan = to_ioat_chan(chan);
> + struct dma_async_tx_descriptor *desc;
>
> if (test_bit(IOAT_CHAN_DOWN, &ioat_chan->state))
> return NULL;
> @@ -669,16 +683,21 @@ ioat_prep_pqxor(struct dma_chan *chan, dma_addr_t dst, dma_addr_t *src,
> if (src_cnt > MAX_SCF)
> return NULL;
>
> + preempt_disable();
preempt_disable() is embedded in get_cpu_var(), no need to open code it.
> + scf = ioat_assign_scratch_buffer();
> +
> memset(scf, 0, src_cnt);
> pq[0] = dst;
> flags |= DMA_PREP_PQ_DISABLE_Q;
> pq[1] = dst; /* specify valid address for disabled result */
>
> - return src_cnt_flags(src_cnt, flags) > 8 ?
> + desc = src_cnt_flags(src_cnt, flags) > 8 ?
> __ioat_prep_pq16_lock(chan, NULL, pq, src, src_cnt, scf, len,
> flags) :
> __ioat_prep_pq_lock(chan, NULL, pq, src, src_cnt, scf, len,
> flags);
> + preempt_enable();
put_cpu_var()...
--
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