| Message ID | 20230615084301.97701-5-zhangpeng.00@bytedance.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | Optimize the fast path of mas_store() | expand |
* Peng Zhang <zhangpeng.00@bytedance.com> [230615 04:43]: > When expanding a range in two directions, only partially overwriting the > previous and next ranges, the number of entries will not be increased, so > we can just update the pivots as a fast path. However, it may introduce > potential risks in RCU mode (although it may pass the test), because it > updates two pivots. We only enable it in non-RCU mode for now. You've fixed the above test passing without the RCU bit set, so this comment should be removed. > > Signed-off-by: Peng Zhang <zhangpeng.00@bytedance.com> > --- > lib/maple_tree.c | 36 ++++++++++++++++++++++++------------ > 1 file changed, 24 insertions(+), 12 deletions(-) > > diff --git a/lib/maple_tree.c b/lib/maple_tree.c > index da4af6743b30..bff6531fd0bc 100644 > --- a/lib/maple_tree.c > +++ b/lib/maple_tree.c > @@ -4100,23 +4100,35 @@ static inline bool mas_wr_slot_store(struct ma_wr_state *wr_mas) > { > struct ma_state *mas = wr_mas->mas; > unsigned char offset = mas->offset; > + void __rcu **slots = wr_mas->slots; > bool gap = false; > > - if (wr_mas->offset_end - offset != 1) > - return false; > - > - gap |= !mt_slot_locked(mas->tree, wr_mas->slots, offset); > - gap |= !mt_slot_locked(mas->tree, wr_mas->slots, offset + 1); > + gap |= !mt_slot_locked(mas->tree, slots, offset); > + gap |= !mt_slot_locked(mas->tree, slots, offset + 1); > > - if (mas->index == wr_mas->r_min) { > - /* Overwriting the range and over a part of the next range. */ > - rcu_assign_pointer(wr_mas->slots[offset], wr_mas->entry); > - wr_mas->pivots[offset] = mas->last; > - } else { > - /* Overwriting a part of the range and over the next range */ > - rcu_assign_pointer(wr_mas->slots[offset + 1], wr_mas->entry); > + if (wr_mas->offset_end - offset == 1) { > + if (mas->index == wr_mas->r_min) { > + /* Overwriting the range and a part of the next one */ > + rcu_assign_pointer(slots[offset], wr_mas->entry); > + wr_mas->pivots[offset] = mas->last; > + } else { > + /* Overwriting a part of the range and the next one */ > + rcu_assign_pointer(slots[offset + 1], wr_mas->entry); > + wr_mas->pivots[offset] = mas->index - 1; > + mas->offset++; /* Keep mas accurate. */ > + } > + } else if (!mt_in_rcu(mas->tree)) { > + /* > + * Expand the range, only partially overwriting the previous and > + * next ranges > + */ > + gap |= !mt_slot_locked(mas->tree, slots, offset + 2); > + rcu_assign_pointer(slots[offset + 1], wr_mas->entry); > wr_mas->pivots[offset] = mas->index - 1; > + wr_mas->pivots[offset + 1] = mas->last; > mas->offset++; /* Keep mas accurate. */ > + } else { > + return false; > } > > trace_ma_write(__func__, mas, 0, wr_mas->entry); > -- > 2.20.1 >
diff --git a/lib/maple_tree.c b/lib/maple_tree.c index da4af6743b30..bff6531fd0bc 100644 --- a/lib/maple_tree.c +++ b/lib/maple_tree.c @@ -4100,23 +4100,35 @@ static inline bool mas_wr_slot_store(struct ma_wr_state *wr_mas) { struct ma_state *mas = wr_mas->mas; unsigned char offset = mas->offset; + void __rcu **slots = wr_mas->slots; bool gap = false; - if (wr_mas->offset_end - offset != 1) - return false; - - gap |= !mt_slot_locked(mas->tree, wr_mas->slots, offset); - gap |= !mt_slot_locked(mas->tree, wr_mas->slots, offset + 1); + gap |= !mt_slot_locked(mas->tree, slots, offset); + gap |= !mt_slot_locked(mas->tree, slots, offset + 1); - if (mas->index == wr_mas->r_min) { - /* Overwriting the range and over a part of the next range. */ - rcu_assign_pointer(wr_mas->slots[offset], wr_mas->entry); - wr_mas->pivots[offset] = mas->last; - } else { - /* Overwriting a part of the range and over the next range */ - rcu_assign_pointer(wr_mas->slots[offset + 1], wr_mas->entry); + if (wr_mas->offset_end - offset == 1) { + if (mas->index == wr_mas->r_min) { + /* Overwriting the range and a part of the next one */ + rcu_assign_pointer(slots[offset], wr_mas->entry); + wr_mas->pivots[offset] = mas->last; + } else { + /* Overwriting a part of the range and the next one */ + rcu_assign_pointer(slots[offset + 1], wr_mas->entry); + wr_mas->pivots[offset] = mas->index - 1; + mas->offset++; /* Keep mas accurate. */ + } + } else if (!mt_in_rcu(mas->tree)) { + /* + * Expand the range, only partially overwriting the previous and + * next ranges + */ + gap |= !mt_slot_locked(mas->tree, slots, offset + 2); + rcu_assign_pointer(slots[offset + 1], wr_mas->entry); wr_mas->pivots[offset] = mas->index - 1; + wr_mas->pivots[offset + 1] = mas->last; mas->offset++; /* Keep mas accurate. */ + } else { + return false; } trace_ma_write(__func__, mas, 0, wr_mas->entry);
When expanding a range in two directions, only partially overwriting the previous and next ranges, the number of entries will not be increased, so we can just update the pivots as a fast path. However, it may introduce potential risks in RCU mode (although it may pass the test), because it updates two pivots. We only enable it in non-RCU mode for now. Signed-off-by: Peng Zhang <zhangpeng.00@bytedance.com> --- lib/maple_tree.c | 36 ++++++++++++++++++++++++------------ 1 file changed, 24 insertions(+), 12 deletions(-)