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authorNeilBrown <neilb@suse.de>2022-01-14 14:07:14 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2022-01-15 16:30:29 +0200
commit4034247a0d6ab281ba3293798ce67af494d86129 (patch)
tree888a53c1c79490500c719b46894267e4f445264a /include/linux/sched
parent704687deaae768a818d7da0584ee021793a97684 (diff)
mm: introduce memalloc_retry_wait()
Various places in the kernel - largely in filesystems - respond to a memory allocation failure by looping around and re-trying. Some of these cannot conveniently use __GFP_NOFAIL, for reasons such as: - a GFP_ATOMIC allocation, which __GFP_NOFAIL doesn't work on - a need to check for the process being signalled between failures - the possibility that other recovery actions could be performed - the allocation is quite deep in support code, and passing down an extra flag to say if __GFP_NOFAIL is wanted would be clumsy. Many of these currently use congestion_wait() which (in almost all cases) simply waits the given timeout - congestion isn't tracked for most devices. It isn't clear what the best delay is for loops, but it is clear that the various filesystems shouldn't be responsible for choosing a timeout. This patch introduces memalloc_retry_wait() with takes on that responsibility. Code that wants to retry a memory allocation can call this function passing the GFP flags that were used. It will wait however is appropriate. For now, it only considers __GFP_NORETRY and whatever gfpflags_allow_blocking() tests. If blocking is allowed without __GFP_NORETRY, then alloc_page either made some reclaim progress, or waited for a while, before failing. So there is no need for much further waiting. memalloc_retry_wait() will wait until the current jiffie ends. If this condition is not met, then alloc_page() won't have waited much if at all. In that case memalloc_retry_wait() waits about 200ms. This is the delay that most current loops uses. linux/sched/mm.h needs to be included in some files now, but linux/backing-dev.h does not. Link: https://lkml.kernel.org/r/163754371968.13692.1277530886009912421@noble.neil.brown.name Signed-off-by: NeilBrown <neilb@suse.de> Cc: Dave Chinner <david@fromorbit.com> Cc: Michal Hocko <mhocko@suse.com> Cc: "Theodore Ts'o" <tytso@mit.edu> Cc: Jaegeuk Kim <jaegeuk@kernel.org> Cc: Chao Yu <chao@kernel.org> Cc: Darrick J. Wong <djwong@kernel.org> Cc: Chuck Lever <chuck.lever@oracle.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'include/linux/sched')
-rw-r--r--include/linux/sched/mm.h26
1 files changed, 26 insertions, 0 deletions
diff --git a/include/linux/sched/mm.h b/include/linux/sched/mm.h
index aca874d33fe6..aa5f09ca5bcf 100644
--- a/include/linux/sched/mm.h
+++ b/include/linux/sched/mm.h
@@ -214,6 +214,32 @@ static inline void fs_reclaim_acquire(gfp_t gfp_mask) { }
static inline void fs_reclaim_release(gfp_t gfp_mask) { }
#endif
+/* Any memory-allocation retry loop should use
+ * memalloc_retry_wait(), and pass the flags for the most
+ * constrained allocation attempt that might have failed.
+ * This provides useful documentation of where loops are,
+ * and a central place to fine tune the waiting as the MM
+ * implementation changes.
+ */
+static inline void memalloc_retry_wait(gfp_t gfp_flags)
+{
+ /* We use io_schedule_timeout because waiting for memory
+ * typically included waiting for dirty pages to be
+ * written out, which requires IO.
+ */
+ __set_current_state(TASK_UNINTERRUPTIBLE);
+ gfp_flags = current_gfp_context(gfp_flags);
+ if (gfpflags_allow_blocking(gfp_flags) &&
+ !(gfp_flags & __GFP_NORETRY))
+ /* Probably waited already, no need for much more */
+ io_schedule_timeout(1);
+ else
+ /* Probably didn't wait, and has now released a lock,
+ * so now is a good time to wait
+ */
+ io_schedule_timeout(HZ/50);
+}
+
/**
* might_alloc - Mark possible allocation sites
* @gfp_mask: gfp_t flags that would be used to allocate