> On 28 May 2018, at 10.58, Matias Bjørling <mb@xxxxxxxxxxx> wrote:
>
> From: Marcin Dziegielewski <marcin.dziegielewski@xxxxxxxxx>
>
> Some devices can expose mw_cunits equal to 0, it can cause creation
> of too small write buffer and cause performance to drop on write
> workloads.
>
> To handle that, we use the default value for MLC and beacause it
> covers both 1.2 and 2.0 OC specification, setting up mw_cunits
> in nvme_nvm_setup_12 function isn't longer necessary.
>
> Signed-off-by: Marcin Dziegielewski <marcin.dziegielewski@xxxxxxxxx>
> Signed-off-by: Igor Konopko <igor.j.konopko@xxxxxxxxx>
> Signed-off-by: Matias Bjørling <mb@xxxxxxxxxxx>
> ---
> drivers/lightnvm/pblk-init.c | 10 +++++++++-
> drivers/nvme/host/lightnvm.c | 1 -
> 2 files changed, 9 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/lightnvm/pblk-init.c b/drivers/lightnvm/pblk-init.c
> index d65d2f972ccf..0f277744266b 100644
> --- a/drivers/lightnvm/pblk-init.c
> +++ b/drivers/lightnvm/pblk-init.c
> @@ -356,7 +356,15 @@ static int pblk_core_init(struct pblk *pblk)
> atomic64_set(&pblk->nr_flush, 0);
> pblk->nr_flush_rst = 0;
>
> - pblk->pgs_in_buffer = geo->mw_cunits * geo->all_luns;
> + if (geo->mw_cunits) {
> + pblk->pgs_in_buffer = geo->mw_cunits * geo->all_luns;
> + } else {
> + pblk->pgs_in_buffer = (geo->ws_opt << 3) * geo->all_luns;
> + /*
> + * Some devices can expose mw_cunits equal to 0, so let's use
> + * here default safe value for MLC.
> + */
> + }
>
> pblk->min_write_pgs = geo->ws_opt * (geo->csecs / PAGE_SIZE);
> max_write_ppas = pblk->min_write_pgs * geo->all_luns;
> diff --git a/drivers/nvme/host/lightnvm.c b/drivers/nvme/host/lightnvm.c
> index 41279da799ed..c747792da915 100644
> --- a/drivers/nvme/host/lightnvm.c
> +++ b/drivers/nvme/host/lightnvm.c
> @@ -338,7 +338,6 @@ static int nvme_nvm_setup_12(struct nvme_nvm_id12 *id,
>
> geo->ws_min = sec_per_pg;
> geo->ws_opt = sec_per_pg;
> - geo->mw_cunits = geo->ws_opt << 3; /* default to MLC safe values */
>
> /* Do not impose values for maximum number of open blocks as it is
> * unspecified in 1.2. Users of 1.2 must be aware of this and eventually
> --
> 2.11.0
By doing this, 1.2 future users (beyond pblk), will fail to have a valid
mw_cunits value. It's ok to deal with the 0 case in pblk, but I believe
that we should have the default value for 1.2 either way.
A more generic way of doing this would be to have a default value for
2.0 too, in case mw_cunits is reported as 0.
Javier
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