Messages in this thread | | | Date | Wed, 11 Oct 2023 15:40:17 +0800 | Subject | Re: [PATCH 2/3] maple_tree: use preallocations in mas_store_gfp() | From | Peng Zhang <> |
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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@oracle.com> >>> --- >>> 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@bytedance.com/ > > 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); >> > >
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