From: "Dziegielewski, Marcin" <marcin.dziegielewski@intel.com>
To: Javier Gonzalez <javier@cnexlabs.com>
Cc: Matias Bjorling <mb@lightnvm.io>, Jens Axboe <axboe@fb.com>,
"linux-block@vger.kernel.org" <linux-block@vger.kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"Konopko, Igor J" <igor.j.konopko@intel.com>
Subject: RE: [GIT PULL 18/20] lightnvm: pblk: handle case when mw_cunits equals to 0
Date: Mon, 4 Jun 2018 11:11:45 +0000 [thread overview]
Message-ID: <9FC4315EA6BEAA449828D92CF173A10D3E3833ED@IRSMSX109.ger.corp.intel.com> (raw)
In-Reply-To: <3B216FC2-D5EB-4A36-8946-27307DA3D1B1@cnexlabs.com>
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WARNING: multiple messages have this Message-ID (diff)
From: "Dziegielewski, Marcin" <marcin.dziegielewski@intel.com>
To: Javier Gonzalez <javier@cnexlabs.com>
Cc: Matias Bjorling <mb@lightnvm.io>, Jens Axboe <axboe@fb.com>,
"linux-block@vger.kernel.org" <linux-block@vger.kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"Konopko, Igor J" <igor.j.konopko@intel.com>
Subject: RE: [GIT PULL 18/20] lightnvm: pblk: handle case when mw_cunits equals to 0
Date: Mon, 4 Jun 2018 11:11:45 +0000 [thread overview]
Message-ID: <9FC4315EA6BEAA449828D92CF173A10D3E3833ED@IRSMSX109.ger.corp.intel.com> (raw)
In-Reply-To: <3B216FC2-D5EB-4A36-8946-27307DA3D1B1@cnexlabs.com>
> -----Original Message-----
> From: Javier Gonzalez [mailto:javier@cnexlabs.com]
> Sent: Monday, June 4, 2018 12:22 PM
> To: Dziegielewski, Marcin <marcin.dziegielewski@intel.com>
> Cc: Matias Bjørling <mb@lightnvm.io>; Jens Axboe <axboe@fb.com>; linux-
> block@vger.kernel.org; linux-kernel@vger.kernel.org; Konopko, Igor J
> <igor.j.konopko@intel.com>
> Subject: Re: [GIT PULL 18/20] lightnvm: pblk: handle case when mw_cunits
> equals to 0
>
> > On 4 Jun 2018, at 12.09, Dziegielewski, Marcin
> <marcin.dziegielewski@intel.com> wrote:
> >
> >
> > Frist of all I want to say sorry for late response - I was on holiday.
> >
> >> From: Javier Gonzalez [mailto:javier@cnexlabs.com]
> >> Sent: Monday, May 28, 2018 1:03 PM
> >> To: Matias Bjørling <mb@lightnvm.io>
> >> Cc: Jens Axboe <axboe@fb.com>; linux-block@vger.kernel.org; linux-
> >> kernel@vger.kernel.org; Dziegielewski, Marcin
> >> <marcin.dziegielewski@intel.com>; Konopko, Igor J
> >> <igor.j.konopko@intel.com>
> >> Subject: Re: [GIT PULL 18/20] lightnvm: pblk: handle case when
> >> mw_cunits equals to 0
> >>
> >>> On 28 May 2018, at 10.58, Matias Bjørling <mb@lightnvm.io> wrote:
> >>>
> >>> From: Marcin Dziegielewski <marcin.dziegielewski@intel.com>
> >>>
> >>> 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@intel.com>
> >>> Signed-off-by: Igor Konopko <igor.j.konopko@intel.com>
> >>> Signed-off-by: Matias Bjørling <mb@lightnvm.io>
> >>> ---
> >>> 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.
> >
> > I'm not sure. From my understanding, setting of default value was
> > workaround for pblk case, am I right ?.
>
> The default value covers the MLC case directly at the lightnvm layer, as
> opposed to doing it directly in pblk. Since pblk is the only user now, you can
> argue that all changes in the lightnvm layer are to solve pblk issues, but the
> idea is that the geometry should be generic.
>
> > In my opinion any user of 1.2
> > spec should be aware that there is not mw_cunit value. From my point
> > of view, leaving here 0 (and decision what do with it to lightnvm
> > user) is more safer way, but maybe I'm wrong. I believe that it is
> > topic to wider discussion with maintainers.
> >
>
> 1.2 and 2.0 have different geometries, but when we designed the common
> nvm_geo structure, the idea was to abstract both specs and allow the upper
> layers to use the geometry transparently.
>
> Specifically in pblk, I would prefer to keep it in such a way that we don't need
> to media specific policies (e.g., set default values for MLC memories), as a
> general design principle. We already do some geometry version checks to
> avoid dereferencing unnecessary pointers on the fast path, which I would
> eventually like to remove.
>
Ok, now I understand your point of view and agree with that, I will prepare second version of this patch without this change. Thanks for the clarification.
> >> 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.
> >
> > Since 0 is correct value and users can make different decisions based
> > on it, I think we shouldn't overwrite it by default value. Is it make
> > sense?
>
> Here I meant at a pblk level - I should have specified it. At the geometry
> level, we should not change it.
>
> The case I am thinking is if mw_cuints repoints 0, but ws_min > 0. In this case,
> we still need a host side buffer to serve < ws_min I/Os, even though the
> device does not require the buffer to guarantee reads.
Oh, ok now we are on the same page. In this patch I was trying to address such case. Do you have other idea how to do it or here are you thinking only on value of default variable?
>
> >> Javier
> >
> > Thanks,
> > Marcin
>
> Javier
Thanks,
Marcin
next prev parent reply other threads:[~2018-06-04 11:11 UTC|newest]
Thread overview: 43+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-05-28 8:58 [GIT PULL 00/20] lightnvm updates for 4.18 Matias Bjørling
2018-05-28 8:58 ` [GIT PULL 01/20] lightnvm: pblk: fail gracefully on line alloc. failure Matias Bjørling
2018-05-28 8:58 ` [GIT PULL 02/20] lightnvm: pblk: recheck for bad lines at runtime Matias Bjørling
2018-05-28 8:58 ` [GIT PULL 03/20] lightnvm: pblk: check read lba on gc path Matias Bjørling
2018-05-28 8:58 ` [GIT PULL 04/20] lightnvm: pblk: improve error msg on corrupted LBAs Matias Bjørling
2018-05-28 8:58 ` [GIT PULL 05/20] lightnvm: pblk: warn in case of corrupted write buffer Matias Bjørling
2018-05-28 8:58 ` [GIT PULL 06/20] lightnvm: pblk: return NVM_ error on failed submission Matias Bjørling
2018-05-28 8:58 ` [GIT PULL 07/20] lightnvm: pblk: remove unnecessary indirection Matias Bjørling
2018-05-28 8:58 ` [GIT PULL 08/20] lightnvm: pblk: remove unnecessary argument Matias Bjørling
2018-05-28 8:58 ` [GIT PULL 09/20] lightnvm: pblk: check for chunk size before allocating it Matias Bjørling
2018-05-28 8:58 ` [GIT PULL 10/20] lightnvm: pass flag on graceful teardown to targets Matias Bjørling
2018-05-28 8:58 ` [GIT PULL 11/20] lightnvm: pblk: remove dead function Matias Bjørling
2018-05-28 8:58 ` [GIT PULL 12/20] lightnvm: pblk: rework write error recovery path Matias Bjørling
2018-05-28 8:58 ` [GIT PULL 13/20] lightnvm: pblk: garbage collect lines with failed writes Matias Bjørling
2018-05-28 8:58 ` [GIT PULL 14/20] lightnvm: pblk: fix smeta write error path Matias Bjørling
2018-05-28 8:58 ` [GIT PULL 15/20] lightnvm: proper error handling for pblk_bio_add_pages Matias Bjørling
2018-05-28 8:58 ` [GIT PULL 16/20] lightnvm: error handling when whole line is bad Matias Bjørling
2018-05-28 10:59 ` Javier Gonzalez
2018-05-29 13:15 ` Konopko, Igor J
2018-05-29 18:29 ` Javier Gonzalez
2018-05-28 8:58 ` [GIT PULL 17/20] lightnvm: fix partial read error path Matias Bjørling
2018-05-28 8:58 ` [GIT PULL 18/20] lightnvm: pblk: handle case when mw_cunits equals to 0 Matias Bjørling
2018-05-28 11:02 ` Javier Gonzalez
2018-06-04 10:09 ` Dziegielewski, Marcin
2018-06-04 10:09 ` Dziegielewski, Marcin
2018-06-04 10:21 ` Javier Gonzalez
2018-06-04 10:21 ` Javier Gonzalez
2018-06-04 11:11 ` Dziegielewski, Marcin [this message]
2018-06-04 11:11 ` Dziegielewski, Marcin
2018-06-04 11:15 ` Javier Gonzalez
2018-06-04 11:15 ` Javier Gonzalez
2018-06-04 17:17 ` Dziegielewski, Marcin
2018-06-04 17:17 ` Dziegielewski, Marcin
2018-06-05 7:12 ` Javier Gonzalez
2018-06-05 9:18 ` Dziegielewski, Marcin
2018-05-28 8:58 ` [GIT PULL 19/20] lightnvm: pblk: add possibility to set write buffer size manually Matias Bjørling
2018-05-28 8:58 ` [GIT PULL 20/20] lightnvm: pblk: sync RB and RL states during GC Matias Bjørling
2018-05-28 10:51 ` Javier Gonzalez
2018-05-29 13:07 ` Konopko, Igor J
2018-05-29 17:58 ` Javier Gonzalez
2018-06-01 10:45 ` [GIT PULL 00/20] lightnvm updates for 4.18 Matias Bjørling
2018-06-01 12:36 ` Jens Axboe
2018-06-01 12:36 ` Jens Axboe
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