在 2023/10/11 08:17, Sidhartha Kumar 写道:
On 10/9/23 8:03 PM, Peng Zhang wrote:
Hi,
在 2023/10/10 04:16, Sidhartha Kumar 写道:
Preallocate maple nodes before call to mas_wr_store_entry(). If a new
node is not needed, go directly to mas_wr_store_entry(), otherwise
allocate the needed nodes and set the MA_STATE_PREALLOC flag.
Signed-off-by: Sidhartha Kumar <sidhartha.kumar@xxxxxxxxxx>
---
lib/maple_tree.c | 22 +++++++++++++++++++---
1 file changed, 19 insertions(+), 3 deletions(-)
diff --git a/lib/maple_tree.c b/lib/maple_tree.c
index e239197a57fc..25ae66e585f4 100644
--- a/lib/maple_tree.c
+++ b/lib/maple_tree.c
@@ -5478,17 +5478,33 @@ int mas_prealloc_calc(struct ma_wr_state *wr_mas)
int mas_store_gfp(struct ma_state *mas, void *entry, gfp_t gfp)
{
MA_WR_STATE(wr_mas, mas, entry);
+ int request;
mas_wr_store_setup(&wr_mas);
- trace_ma_write(__func__, mas, 0, entry);
-retry:
+ wr_mas.content = mas_start(mas);
+
+ request = mas_prealloc_calc(&wr_mas);
mas_wr_store_entry() does something similar to mas_prealloc_calc().
Now, making it do it twice would incur additional overhead.
We encountered this issue while optimizing preallocation, but it
hasn't been resolved yet. Previously, this problem only occurred
when using mas_preallocate(). Now, this change would bring this
impact to all write operations on maple tree. What do you think
about it?
After talking to Liam, I will have to implement the store type enum feature on the Maple Tree Work list so that mas_prealloc_calc() can start a partial walk and write that information to the enum. mas_wr_store_entry() can then read that enum to continue the walk that was already started rather than having to redo the whole walk. This could also be used in mas_preallocate(). Do you have any suggestions for the implementation of this enum?
There is another scenario where this enum can be useful,
as seen in the implementation of mas_replace_entry() in [1].
It is a faster alternative to mas_store(), but it is not safe.
If we can determine through the enum while writing the maple
tree that a faster write operation can be performed, it would
be beneficial. Some performance improvements can also be
observed in [1].
[1] https://lore.kernel.org/lkml/49f0181a-55a4-41aa-8596-877560c8b802@xxxxxxxxxxxxx/
Thanks,
Sid
Thanks,
Peng
+ if (!request)
+ goto store_entry;
+
+ mas_node_count_gfp(mas, request, gfp);
+ if (unlikely(mas_is_err(mas))) {
+ mas_set_alloc_req(mas, 0);
+ mas_destroy(mas);
+ mas_reset(mas);
+ return xa_err(mas->node);
+ }
+ mas->mas_flags |= MA_STATE_PREALLOC;
+
+store_entry:
mas_wr_store_entry(&wr_mas);
if (unlikely(mas_nomem(mas, gfp)))
- goto retry;
+ goto store_entry;
if (unlikely(mas_is_err(mas)))
return xa_err(mas->node);
+ trace_ma_write(__func__, mas, 0, entry);
return 0;
}
EXPORT_SYMBOL_GPL(mas_store_gfp);
