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V.'s message of "Tue, 20 Feb 2024 13:23:59 +0530") References: <9c3f7b743477560d1c5b12b8c111a584a2cc92ee.1708097962.git.donettom@linux.ibm.com> <8d7737208bd24e754dc7a538a3f7f02de84f1f72.1708097962.git.donettom@linux.ibm.com> <877cizppsa.fsf@yhuang6-desk2.ccr.corp.intel.com> <87sf1nzi3s.fsf@kernel.org> Date: Tue, 20 Feb 2024 15:58:08 +0800 Message-ID: <87ttm3o9db.fsf@yhuang6-desk2.ccr.corp.intel.com> User-Agent: Gnus/5.13 (Gnus v5.13) MIME-Version: 1.0 Content-Type: text/plain; charset=ascii X-Rspamd-Queue-Id: 30BE7120020 X-Rspam-User: X-Rspamd-Server: rspam02 X-Stat-Signature: atgsighdmmud5bfcwgwk6uz55ii5p84u X-HE-Tag: 1708416009-612724 X-HE-Meta: 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 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: List-Subscribe: List-Unsubscribe: Aneesh Kumar K.V writes: > "Huang, Ying" writes: > >> Donet Tom writes: >> >>> commit bda420b98505 ("numa balancing: migrate on fault among multiple bound >>> nodes") added support for migrate on protnone reference with MPOL_BIND >>> memory policy. This allowed numa fault migration when the executing node >>> is part of the policy mask for MPOL_BIND. This patch extends migration >>> support to MPOL_PREFERRED_MANY policy. >>> >>> Currently, we cannot specify MPOL_PREFERRED_MANY with the mempolicy flag >>> MPOL_F_NUMA_BALANCING. This causes issues when we want to use >>> NUMA_BALANCING_MEMORY_TIERING. To effectively use the slow memory tier, >>> the kernel should not allocate pages from the slower memory tier via >>> allocation control zonelist fallback. Instead, we should move cold pages >>> from the faster memory node via memory demotion. For a page allocation, >>> kswapd is only woken up after we try to allocate pages from all nodes in >>> the allocation zone list. This implies that, without using memory >>> policies, we will end up allocating hot pages in the slower memory tier. >>> >>> MPOL_PREFERRED_MANY was added by commit b27abaccf8e8 ("mm/mempolicy: add >>> MPOL_PREFERRED_MANY for multiple preferred nodes") to allow better >>> allocation control when we have memory tiers in the system. With >>> MPOL_PREFERRED_MANY, the user can use a policy node mask consisting only >>> of faster memory nodes. When we fail to allocate pages from the faster >>> memory node, kswapd would be woken up, allowing demotion of cold pages >>> to slower memory nodes. >>> >>> With the current kernel, such usage of memory policies implies we can't >>> do page promotion from a slower memory tier to a faster memory tier >>> using numa fault. This patch fixes this issue. >>> >>> For MPOL_PREFERRED_MANY, if the executing node is in the policy node >>> mask, we allow numa migration to the executing nodes. If the executing >>> node is not in the policy node mask but the folio is already allocated >>> based on policy preference (the folio node is in the policy node mask), >>> we don't allow numa migration. If both the executing node and folio node >>> are outside the policy node mask, we allow numa migration to the >>> executing nodes. >>> >>> Signed-off-by: Aneesh Kumar K.V (IBM) >>> Signed-off-by: Donet Tom >>> --- >>> mm/mempolicy.c | 28 ++++++++++++++++++++++++++-- >>> 1 file changed, 26 insertions(+), 2 deletions(-) >>> >>> diff --git a/mm/mempolicy.c b/mm/mempolicy.c >>> index 73d698e21dae..8c4c92b10371 100644 >>> --- a/mm/mempolicy.c >>> +++ b/mm/mempolicy.c >>> @@ -1458,9 +1458,10 @@ static inline int sanitize_mpol_flags(int *mode, unsigned short *flags) >>> if ((*flags & MPOL_F_STATIC_NODES) && (*flags & MPOL_F_RELATIVE_NODES)) >>> return -EINVAL; >>> if (*flags & MPOL_F_NUMA_BALANCING) { >>> - if (*mode != MPOL_BIND) >>> + if (*mode == MPOL_BIND || *mode == MPOL_PREFERRED_MANY) >>> + *flags |= (MPOL_F_MOF | MPOL_F_MORON); >>> + else >>> return -EINVAL; >>> - *flags |= (MPOL_F_MOF | MPOL_F_MORON); >>> } >>> return 0; >>> } >>> @@ -2463,6 +2464,23 @@ static void sp_free(struct sp_node *n) >>> kmem_cache_free(sn_cache, n); >>> } >>> >>> +static inline bool mpol_preferred_should_numa_migrate(int exec_node, int folio_node, >>> + struct mempolicy *pol) >>> +{ >>> + /* if the executing node is in the policy node mask, migrate */ >>> + if (node_isset(exec_node, pol->nodes)) >>> + return true; >>> + >>> + /* If the folio node is in policy node mask, don't migrate */ >>> + if (node_isset(folio_node, pol->nodes)) >>> + return false; >>> + /* >>> + * both the folio node and executing node are outside the policy nodemask, >>> + * migrate as normal numa fault migration. >>> + */ >>> + return true; >> >> Why? This may cause some unexpected result. For example, pages may be >> distributed among multiple sockets unexpectedly. So, I prefer the more >> conservative policy, that is, only migrate if this node is in >> pol->nodes. >> > > This will only have an impact if the user specifies > MPOL_F_NUMA_BALANCING. This means that the user is explicitly requesting > for frequently accessed memory pages to be migrated. Memory policy > MPOL_PREFERRED_MANY is able to allocate pages from nodes outside of > policy->nodes. For the specific use case that I am interested in, it > should be okay to restrict it to policy->nodes. However, I am wondering > if this is too restrictive given the definition of MPOL_PREFERRED_MANY. IMHO, we can start with some consecutive way and expand it if it's proved necessary. -- Best Regards, Huang, Ying