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Howlett" , Wei Yang , akpm@linux-foundation.org, maple-tree@lists.infradead.org, linux-mm@kvack.org Subject: Re: [PATCH 2/2] maple_tree: memset maple_big_node as a whole Message-ID: <20240908093421.xsndoh2hcu4xl7td@master> Reply-To: Wei Yang References: <20240907084927.1547-1-richard.weiyang@gmail.com> <20240907084927.1547-2-richard.weiyang@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: NeoMutt/20170113 (1.7.2) X-Stat-Signature: ryzsdioeqp1uybgmi7rusmj58yyqys1j X-Rspamd-Queue-Id: 54073100002 X-Rspam-User: X-Rspamd-Server: rspam08 X-HE-Tag: 1725788065-325095 X-HE-Meta: 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 llOGEyTW 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000061, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Sat, Sep 07, 2024 at 09:29:01AM -0400, Liam R. Howlett wrote: >* Wei Yang [240907 04:50]: >> In maple_big_node, we define slot and padding/gap in a union. And based >> on current definition of MAPLE_BIG_NODE_SLOTS/GAPS, padding is always >> less then slot and part of the gap is overlapped by slot. > ^^^^- than > >> >> For example on 64bit system: >> >> MAPLE_BIG_NODE_SLOT is 34 >> MAPLE_BIG_NODE_GAP is 21 >> >> With this knowledge, current code actually clear the whole >> maple_big_node and even clear some space twice. >> >> Instead of clear maple_big_node each field separately, let's clear it in >> one memset. >> >> Signed-off-by: Wei Yang >> CC: Liam R. Howlett >> >> --- >> Liam: >> >> This looks obvious, so I just run the ./maple test to see it doesn't >> break anything. >> > >The big node also includes the type, which isn't cleared. However it is >unconditionally set below, so your change log is not correct in the >statement that it is fully cleared, but the code will work and it is >worth fixing what you have found. > I will mention this next time. >If you are sending more than one patch, it is better to make a >cover letter to explain your series. > Ok, I will add a cover letter next time. >It is probably worth re-spinning the series to fix the comment, but >these changes look good. I'll have a closer look later. > Thank, I will re-arrange the change log and add a cover letter for v2. >> Do you think I need to add a benchmark and run a perf for this kind of >> change? > >No, you are doing less work so this should be better as long as it is >correct. Zeroing can be expensive on some archs so this is good. > >> --- >> lib/maple_tree.c | 5 +---- >> 1 file changed, 1 insertion(+), 4 deletions(-) >> >> diff --git a/lib/maple_tree.c b/lib/maple_tree.c >> index d8f10773e451..911c5e04e634 100644 >> --- a/lib/maple_tree.c >> +++ b/lib/maple_tree.c >> @@ -3134,10 +3134,7 @@ static inline void mast_fill_bnode(struct maple_subtree_state *mast, >> bool cp = true; >> unsigned char split; >> >> - memset(mast->bn->gap, 0, sizeof(unsigned long) * ARRAY_SIZE(mast->bn->gap)); >> - memset(mast->bn->slot, 0, sizeof(unsigned long) * ARRAY_SIZE(mast->bn->slot)); >> - memset(mast->bn->pivot, 0, sizeof(unsigned long) * ARRAY_SIZE(mast->bn->pivot)); >> - mast->bn->b_end = 0; >> + memset(mast->bn, 0, sizeof(struct maple_big_node)); >> >> if (mte_is_root(mas->node)) { >> cp = false; >> -- >> 2.34.1 >> -- Wei Yang Help you, Help me