| Message ID | 20191016095438.12391-3-urezki@gmail.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [v3,1/3] mm/vmalloc: remove preempt_disable/enable when do preloading | expand |
On Wed 16-10-19 11:54:38, Uladzislau Rezki (Sony) wrote: > When fit type is NE_FIT_TYPE there is a need in one extra object. > Usually the "ne_fit_preload_node" per-CPU variable has it and > there is no need in GFP_NOWAIT allocation, but there are exceptions. > > This commit just adds more explanations, as a result giving > answers on questions like when it can occur, how often, under > which conditions and what happens if GFP_NOWAIT gets failed. > > Signed-off-by: Uladzislau Rezki (Sony) <urezki@gmail.com> Acked-by: Michal Hocko <mhocko@suse.com> > --- > mm/vmalloc.c | 13 +++++++++++++ > 1 file changed, 13 insertions(+) > > diff --git a/mm/vmalloc.c b/mm/vmalloc.c > index 593bf554518d..2290a0d270e4 100644 > --- a/mm/vmalloc.c > +++ b/mm/vmalloc.c > @@ -969,6 +969,19 @@ adjust_va_to_fit_type(struct vmap_area *va, > * There are a few exceptions though, as an example it is > * a first allocation (early boot up) when we have "one" > * big free space that has to be split. > + * > + * Also we can hit this path in case of regular "vmap" > + * allocations, if "this" current CPU was not preloaded. > + * See the comment in alloc_vmap_area() why. If so, then > + * GFP_NOWAIT is used instead to get an extra object for > + * split purpose. That is rare and most time does not > + * occur. > + * > + * What happens if an allocation gets failed. Basically, > + * an "overflow" path is triggered to purge lazily freed > + * areas to free some memory, then, the "retry" path is > + * triggered to repeat one more time. See more details > + * in alloc_vmap_area() function. > */ > lva = kmem_cache_alloc(vmap_area_cachep, GFP_NOWAIT); > if (!lva) > -- > 2.20.1 >
On Wed, Oct 16, 2019 at 01:07:22PM +0200, Michal Hocko wrote: > On Wed 16-10-19 11:54:38, Uladzislau Rezki (Sony) wrote: > > When fit type is NE_FIT_TYPE there is a need in one extra object. > > Usually the "ne_fit_preload_node" per-CPU variable has it and > > there is no need in GFP_NOWAIT allocation, but there are exceptions. > > > > This commit just adds more explanations, as a result giving > > answers on questions like when it can occur, how often, under > > which conditions and what happens if GFP_NOWAIT gets failed. > > > > Signed-off-by: Uladzislau Rezki (Sony) <urezki@gmail.com> > > Acked-by: Michal Hocko <mhocko@suse.com> > Thanks! -- Vlad Rezki
diff --git a/mm/vmalloc.c b/mm/vmalloc.c index 593bf554518d..2290a0d270e4 100644 --- a/mm/vmalloc.c +++ b/mm/vmalloc.c @@ -969,6 +969,19 @@ adjust_va_to_fit_type(struct vmap_area *va, * There are a few exceptions though, as an example it is * a first allocation (early boot up) when we have "one" * big free space that has to be split. + * + * Also we can hit this path in case of regular "vmap" + * allocations, if "this" current CPU was not preloaded. + * See the comment in alloc_vmap_area() why. If so, then + * GFP_NOWAIT is used instead to get an extra object for + * split purpose. That is rare and most time does not + * occur. + * + * What happens if an allocation gets failed. Basically, + * an "overflow" path is triggered to purge lazily freed + * areas to free some memory, then, the "retry" path is + * triggered to repeat one more time. See more details + * in alloc_vmap_area() function. */ lva = kmem_cache_alloc(vmap_area_cachep, GFP_NOWAIT); if (!lva)
When fit type is NE_FIT_TYPE there is a need in one extra object. Usually the "ne_fit_preload_node" per-CPU variable has it and there is no need in GFP_NOWAIT allocation, but there are exceptions. This commit just adds more explanations, as a result giving answers on questions like when it can occur, how often, under which conditions and what happens if GFP_NOWAIT gets failed. Signed-off-by: Uladzislau Rezki (Sony) <urezki@gmail.com> --- mm/vmalloc.c | 13 +++++++++++++ 1 file changed, 13 insertions(+)