From: Junxian Huang huangjunxian6@hisilicon.com
mainline inclusion from mainline-v6.11-rc5 commit fe51f6254d81f5a69c31df16353d6539b2b51630 category: bugfix bugzilla: https://gitee.com/openeuler/kernel/issues/IAR316 CVE: NA
Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i...
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When allocating MTT hem, for each hop level of each hem that is being allocated, the driver iterates the hem list to find out whether the bt page has been allocated in this hop level. If not, allocate a new one and splice it to the list. The time complexity is O(n^2) in worst cases.
Currently the allocation for-loop uses 'unit' as the step size. This actually has taken into account the reuse of last-hop-level MTT bt pages by multiple buffer pages. Thus pages of last hop level will never have been allocated, so there is no need to iterate the hem list in last hop level.
Removing this unnecessary iteration can reduce the time complexity to O(n).
Fixes: 38389eaa4db1 ("RDMA/hns: Add mtr support for mixed multihop addressing") Signed-off-by: Junxian Huang huangjunxian6@hisilicon.com Link: https://patch.msgid.link/20240906093444.3571619-9-huangjunxian6@hisilicon.co... Signed-off-by: Leon Romanovsky leon@kernel.org Signed-off-by: Xinghai Cen cenxinghai@h-partners.com --- drivers/infiniband/hw/hns/hns_roce_hem.c | 10 ++++++---- 1 file changed, 6 insertions(+), 4 deletions(-)
diff --git a/drivers/infiniband/hw/hns/hns_roce_hem.c b/drivers/infiniband/hw/hns/hns_roce_hem.c index bfe36eb0658d..cdb231e16fe2 100644 --- a/drivers/infiniband/hw/hns/hns_roce_hem.c +++ b/drivers/infiniband/hw/hns/hns_roce_hem.c @@ -1135,10 +1135,12 @@ static int hem_list_alloc_mid_bt(struct hns_roce_dev *hr_dev,
/* config L1 bt to last bt and link them to corresponding parent */ for (level = 1; level < hopnum; level++) { - cur = hem_list_search_item(&mid_bt[level], offset); - if (cur) { - hem_ptrs[level] = cur; - continue; + if (!hem_list_is_bottom_bt(hopnum, level)) { + cur = hem_list_search_item(&mid_bt[level], offset); + if (cur) { + hem_ptrs[level] = cur; + continue; + } }
step = hem_list_calc_ba_range(hopnum, level, unit);