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| author | Uladzislau Rezki (Sony) <urezki@gmail.com> | 2019-12-01 04:54:40 +0300 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2019-12-01 23:59:05 +0300 |
| commit | 060650a2a0598d61bac6ce64578b176cb0e18b06 (patch) | |
| tree | 42477d930b88d2930687c53aa8fbc4de8277b8de | |
| parent | f07116d77b5b9a4fecdcb470fc6ea08378b98ff7 (diff) | |
| download | linux-060650a2a0598d61bac6ce64578b176cb0e18b06.tar.xz | |
mm/vmalloc: add more comments to the adjust_va_to_fit_type()
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.
Link: http://lkml.kernel.org/r/20191016095438.12391-3-urezki@gmail.com
Signed-off-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Daniel Wagner <dwagner@suse.de>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Uladzislau Rezki <urezki@gmail.com>
Cc: Hillf Danton <hdanton@sina.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Oleksiy Avramchenko <oleksiy.avramchenko@sonymobile.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
| -rw-r--r-- | mm/vmalloc.c | 13 |
1 files changed, 13 insertions, 0 deletions
diff --git a/mm/vmalloc.c b/mm/vmalloc.c index b3bb50d07e27..9bb6610f499b 100644 --- a/mm/vmalloc.c +++ b/mm/vmalloc.c @@ -968,6 +968,19 @@ 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) |