| Message ID | 1547047861-7271-3-git-send-email-joshi.k@samsung.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | Write-hint for FS journal | expand |
> On 9 Jan 2019, at 16.30, Kanchan Joshi <joshi.k@samsung.com> wrote: > > Exiting write-hints are exposed to user-mode. There is a possiblity > of conflict if kernel happens to use those. This patch introduces four > write-hints for exclusive kernel-mode use. > > Signed-off-by: Kanchan Joshi <joshi.k@samsung.com> > --- > include/linux/fs.h | 5 +++++ > 1 file changed, 5 insertions(+) > > diff --git a/include/linux/fs.h b/include/linux/fs.h > index 811c777..e8548eb 100644 > --- a/include/linux/fs.h > +++ b/include/linux/fs.h > @@ -291,6 +291,11 @@ enum rw_hint { > WRITE_LIFE_MEDIUM = RWH_WRITE_LIFE_MEDIUM, > WRITE_LIFE_LONG = RWH_WRITE_LIFE_LONG, > WRITE_LIFE_EXTREME = RWH_WRITE_LIFE_EXTREME, > +/* below ones are meant for in-kernel use */ > + KERN_WRITE_LIFE_SHORT, > + KERN_WRITE_LIFE_MEDIUM, > + KERN_WRITE_LIFE_LONG, > + KERN_WRITE_LIFE_EXTREME > }; > I think Jens and Dave meant kernel hints to go top down. This would also give space for supporting more hints / streams from both ends for user and kernel. Javier
On Wed 23-01-19 19:27:12, Javier González wrote: > > > On 9 Jan 2019, at 16.30, Kanchan Joshi <joshi.k@samsung.com> wrote: > > > > Exiting write-hints are exposed to user-mode. There is a possiblity > > of conflict if kernel happens to use those. This patch introduces four > > write-hints for exclusive kernel-mode use. > > > > Signed-off-by: Kanchan Joshi <joshi.k@samsung.com> > > --- > > include/linux/fs.h | 5 +++++ > > 1 file changed, 5 insertions(+) > > > > diff --git a/include/linux/fs.h b/include/linux/fs.h > > index 811c777..e8548eb 100644 > > --- a/include/linux/fs.h > > +++ b/include/linux/fs.h > > @@ -291,6 +291,11 @@ enum rw_hint { > > WRITE_LIFE_MEDIUM = RWH_WRITE_LIFE_MEDIUM, > > WRITE_LIFE_LONG = RWH_WRITE_LIFE_LONG, > > WRITE_LIFE_EXTREME = RWH_WRITE_LIFE_EXTREME, > > +/* below ones are meant for in-kernel use */ > > + KERN_WRITE_LIFE_SHORT, > > + KERN_WRITE_LIFE_MEDIUM, > > + KERN_WRITE_LIFE_LONG, > > + KERN_WRITE_LIFE_EXTREME > > }; > > > > I think Jens and Dave meant kernel hints to go top down. This would also > give space for supporting more hints / streams from both ends for user > and kernel. Yes, that was the idea however if I understand it right, the write hints do not really have to be consistent boot-to-boot since they aren't stored persistently by the disk, are they? If that's the case, it doesn't really matter which numbers we pick. One thing I don't quite like is the naming of KERN_WRITE_LIFE_SHORT etc.. It is upto filesystem to assign meanings to the write hints. So I think it is enough to provide something like KERN_WRITE_HINT_MIN which is the first hint available to the kernel and then the number of hints available to the kernel. Honza
> On 24 Jan 2019, at 09.35, Jan Kara <jack@suse.cz> wrote: > > On Wed 23-01-19 19:27:12, Javier González wrote: >>> On 9 Jan 2019, at 16.30, Kanchan Joshi <joshi.k@samsung.com> wrote: >>> >>> Exiting write-hints are exposed to user-mode. There is a possiblity >>> of conflict if kernel happens to use those. This patch introduces four >>> write-hints for exclusive kernel-mode use. >>> >>> Signed-off-by: Kanchan Joshi <joshi.k@samsung.com> >>> --- >>> include/linux/fs.h | 5 +++++ >>> 1 file changed, 5 insertions(+) >>> >>> diff --git a/include/linux/fs.h b/include/linux/fs.h >>> index 811c777..e8548eb 100644 >>> --- a/include/linux/fs.h >>> +++ b/include/linux/fs.h >>> @@ -291,6 +291,11 @@ enum rw_hint { >>> WRITE_LIFE_MEDIUM = RWH_WRITE_LIFE_MEDIUM, >>> WRITE_LIFE_LONG = RWH_WRITE_LIFE_LONG, >>> WRITE_LIFE_EXTREME = RWH_WRITE_LIFE_EXTREME, >>> +/* below ones are meant for in-kernel use */ >>> + KERN_WRITE_LIFE_SHORT, >>> + KERN_WRITE_LIFE_MEDIUM, >>> + KERN_WRITE_LIFE_LONG, >>> + KERN_WRITE_LIFE_EXTREME >>> }; >> >> I think Jens and Dave meant kernel hints to go top down. This would also >> give space for supporting more hints / streams from both ends for user >> and kernel. > > Yes, that was the idea however if I understand it right, the write hints do > not really have to be consistent boot-to-boot since they aren't stored > persistently by the disk, are they? If that's the case, it doesn't really > matter which numbers we pick. > I guess this is implementation specific. Some times the drive will want to store this to improve GC. For the current "coldness" hint I does not matter much, but if the hint were to express other metric it can become relevant. Anyway, the comment was more to separate user / kernel hints and allow them to grow from the ends. > One thing I don't quite like is the naming of KERN_WRITE_LIFE_SHORT etc.. It > is upto filesystem to assign meanings to the write hints. So I think it is > enough to provide something like KERN_WRITE_HINT_MIN which is the first > hint available to the kernel and then the number of hints available to the > kernel. > Makes sense to me. Then we can rename the hint for each FS to give it proper mening. > Honza > > -- > Jan Kara <jack@suse.com> > SUSE Labs, CR Javier
diff --git a/include/linux/fs.h b/include/linux/fs.h index 811c777..e8548eb 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -291,6 +291,11 @@ enum rw_hint { WRITE_LIFE_MEDIUM = RWH_WRITE_LIFE_MEDIUM, WRITE_LIFE_LONG = RWH_WRITE_LIFE_LONG, WRITE_LIFE_EXTREME = RWH_WRITE_LIFE_EXTREME, +/* below ones are meant for in-kernel use */ + KERN_WRITE_LIFE_SHORT, + KERN_WRITE_LIFE_MEDIUM, + KERN_WRITE_LIFE_LONG, + KERN_WRITE_LIFE_EXTREME }; #define IOCB_EVENTFD (1 << 0)
Exiting write-hints are exposed to user-mode. There is a possiblity of conflict if kernel happens to use those. This patch introduces four write-hints for exclusive kernel-mode use. Signed-off-by: Kanchan Joshi <joshi.k@samsung.com> --- include/linux/fs.h | 5 +++++ 1 file changed, 5 insertions(+)