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charset=us-ascii Content-Disposition: inline In-Reply-To: <4c9d8138-d379-810f-64e7-0d018ed019df@nvidia.com> User-Agent: NeoMutt/20170113 (1.7.2) X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Fri, Mar 27, 2020 at 03:37:57PM -0700, John Hubbard wrote: >On 3/27/20 3:01 PM, Wei Yang wrote: >> Since we always clear node_order before getting it, we can leverage >> compiler to do this instead of at run time. >> >> Signed-off-by: Wei Yang >> --- >> mm/page_alloc.c | 3 +-- >> 1 file changed, 1 insertion(+), 2 deletions(-) >> >> diff --git a/mm/page_alloc.c b/mm/page_alloc.c >> index dfcf2682ed40..49dd1f25c000 100644 >> --- a/mm/page_alloc.c >> +++ b/mm/page_alloc.c >> @@ -5585,7 +5585,7 @@ static void build_thisnode_zonelists(pg_data_t *pgdat) >> static void build_zonelists(pg_data_t *pgdat) >> { >> - static int node_order[MAX_NUMNODES]; >> + static int node_order[MAX_NUMNODES] = {0}; > > >Looks wrong: now the single instance of node_order is initialized just once by >the compiler. And that means that only the first caller of this function >gets a zeroed node_order array... > What a shame on me. You are right, I miss the static word. Well, then I am curious about why we want to define it as static. Each time we call this function, node_order would be set to 0 and find_next_best_node() would sort a proper value into it. I don't see the reason to reserve it in a global area and be used next time. My suggestion is to remove the static and define it {0} instead of memset every time. Is my understanding correct here? > >> int node, load, nr_nodes = 0; >> nodemask_t used_mask = NODE_MASK_NONE; >> int local_node, prev_node; >> @@ -5595,7 +5595,6 @@ static void build_zonelists(pg_data_t *pgdat) >> load = nr_online_nodes; >> prev_node = local_node; >> - memset(node_order, 0, sizeof(node_order)); > >...and all subsequent callers are left with whatever debris is remaining in >node_order. So this is not good. > >The reason that memset() was used here, is that there aren't many other ways >to get node_order zeroed, given that it is a statically defined variable. > > >> while ((node = find_next_best_node(local_node, &used_mask)) >= 0) { >> /* >> * We don't want to pressure a particular node. >> > > > >thanks, >-- >John Hubbard >NVIDIA -- Wei Yang Help you, Help me