On Wed, Jun 19, 2024 at 06:58:27PM +0530, Anand Khoje wrote:
> In non FLR context, at times CX-5 requests release of ~8 million FW pages.
> This needs humongous number of cmd mailboxes, which to be released once
> the pages are reclaimed. Release of humongous number of cmd mailboxes is
> consuming cpu time running into many seconds. Which with non preemptible
> kernels is leading to critical process starving on that cpu’s RQ.
> To alleviate this, this change restricts the total number of pages
> a worker will try to reclaim maximum 50K pages in one go.
> The limit 50K is aligned with the current firmware capacity/limit of
> releasing 50K pages at once per MLX5_CMD_OP_MANAGE_PAGES + MLX5_PAGES_TAKE
> device command.
>
> Our tests have shown significant benefit of this change in terms of
> time consumed by dma_pool_free().
> During a test where an event was raised by HCA
> to release 1.3 Million pages, following observations were made:
>
> - Without this change:
> Number of mailbox messages allocated was around 20K, to accommodate
> the DMA addresses of 1.3 million pages.
> The average time spent by dma_pool_free() to free the DMA pool is between
> 16 usec to 32 usec.
> value ------------- Distribution ------------- count
> 256 | 0
> 512 |@ 287
> 1024 |@@@ 1332
> 2048 |@ 656
> 4096 |@@@@@ 2599
> 8192 |@@@@@@@@@@ 4755
> 16384 |@@@@@@@@@@@@@@@ 7545
> 32768 |@@@@@ 2501
> 65536 | 0
>
> - With this change:
> Number of mailbox messages allocated was around 800; this was to
> accommodate DMA addresses of only 50K pages.
> The average time spent by dma_pool_free() to free the DMA pool in this case
> lies between 1 usec to 2 usec.
> value ------------- Distribution ------------- count
> 256 | 0
> 512 |@@@@@@@@@@@@@@@@@@ 346
> 1024 |@@@@@@@@@@@@@@@@@@@@@@ 435
> 2048 | 0
> 4096 | 0
> 8192 | 1
> 16384 | 0
>
> Signed-off-by: Anand Khoje <anand.a.khoje@xxxxxxxxxx>
> Reviewed-by: Leon Romanovsky <leonro@xxxxxxxxxx>
> ---
> Changes in v4:
> - Fixed a nit in patch subject.
> ---
> drivers/net/ethernet/mellanox/mlx5/core/pagealloc.c | 7 ++++++-
> 1 file changed, 6 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/net/ethernet/mellanox/mlx5/core/pagealloc.c b/drivers/net/ethernet/mellanox/mlx5/core/pagealloc.c
> index dcf58ef..06eee3a 100644
> --- a/drivers/net/ethernet/mellanox/mlx5/core/pagealloc.c
> +++ b/drivers/net/ethernet/mellanox/mlx5/core/pagealloc.c
> @@ -608,6 +608,7 @@ enum {
> RELEASE_ALL_PAGES_MASK = 0x4000,
> };
>
> +#define MAX_RECLAIM_NPAGES -50000
> static int req_pages_handler(struct notifier_block *nb,
> unsigned long type, void *data)
> {
> @@ -639,9 +640,13 @@ static int req_pages_handler(struct notifier_block *nb,
>
> req->dev = dev;
> req->func_id = func_id;
> - req->npages = npages;
> req->ec_function = ec_function;
> req->release_all = release_all;
> + if (npages < MAX_RECLAIM_NPAGES)
> + req->npages = MAX_RECLAIM_NPAGES;
> + else
> + req->npages = npages;
> +
BTW, this can be written as:
req->npages = max_t(s32, npages, MAX_RECLAIM_NPAGES);
Thanks
> INIT_WORK(&req->work, pages_work_handler);
> queue_work(dev->priv.pg_wq, &req->work);
> return NOTIFY_OK;
> --
> 1.8.3.1
>
