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From: "Ho-Ren (Jack) Chuang" Message-ID: <84b43294411bb1fe0ed58f2da59abf554ef48f7d@linux.dev> TLS-Required: No Subject: Re: [PATCH v2 1/1] memory tier: consolidate the initialization of memory tiers To: "Jonathan Cameron" Cc: "Huang, Ying" , "Gregory Price" , aneesh.kumar@linux.ibm.com, mhocko@suse.com, tj@kernel.org, john@jagalactic.com, "Eishan Mirakhur" , "Vinicius Tavares Petrucci" , "Ravis OpenSrc" , "Alistair Popple" , "Srinivasulu Thanneeru" , "SeongJae Park" , "Rafael J. Wysocki" , "Len Brown" , "Andrew Morton" , "Dave Jiang" , "Dan Williams" , linux-acpi@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, "Ho-Ren (Jack) Chuang" , "Ho-Ren (Jack) Chuang" , "Ho-Ren (Jack) Chuang" , linux-cxl@vger.kernel.org, qemu-devel@nongnu.org In-Reply-To: <20240702142535.00003dc0@Huawei.com> References: <20240628060925.303309-1-horen.chuang@linux.dev> <20240628060925.303309-2-horen.chuang@linux.dev> <20240702142535.00003dc0@Huawei.com> X-Migadu-Flow: FLOW_OUT Received-SPF: pass client-ip=91.218.175.185; envelope-from=horen.chuang@linux.dev; helo=out-185.mta0.migadu.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, SPF_HELO_PASS=-0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Hi Jonathan, I appreciate your feedback and valuable suggestions. Replies inlined. July 2, 2024 at 6:25 AM, "Jonathan Cameron" = wrote: >=20 >=20On Fri, 28 Jun 2024 06:09:23 +0000 >=20 >=20"Ho-Ren (Jack) Chuang" wrote: >=20 >=20>=20 >=20> If we simply move the set_node_memory_tier() from memory_tier_init(= ) > >=20 >=20> to late_initcall(), it will result in HMAT not registering > >=20 >=20> the mt_adistance_algorithm callback function, because > >=20 >=20> set_node_memory_tier() is not performed during the memory tiering > >=20 >=20> initialization phase, leading to a lack of correct default_dram > >=20 >=20> information. > >=20 >=20>=20=20 >=20>=20 >=20> Therefore, we introduced a nodemask to pass the information of the > >=20 >=20> default DRAM nodes. The reason for not choosing to reuse > >=20 >=20> default_dram_type->nodes is that it is not clean enough. So in the= end, > >=20 >=20> we use a __initdata variable, which is a variable that is released= once > >=20 >=20> initialization is complete, including both CPU and memory nodes fo= r HMAT > >=20 >=20> to iterate through. > >=20 >=20>=20=20 >=20>=20 >=20> Besides, since default_dram_type may be checked/used during the > >=20 >=20> initialization process of HMAT and drivers, it is better to keep t= he > >=20 >=20> allocation of default_dram_type in memory_tier_init(). > >=20 >=20>=20=20 >=20>=20 >=20> Signed-off-by: Ho-Ren (Jack) Chuang > >=20 >=20> Suggested-by: Jonathan Cameron > >=20 >=20> --- > >=20 >=20> drivers/acpi/numa/hmat.c | 5 +-- > >=20 >=20> include/linux/memory-tiers.h | 2 ++ > >=20 >=20> mm/memory-tiers.c | 59 +++++++++++++++--------------------- > >=20 >=20> 3 files changed, 28 insertions(+), 38 deletions(-) > >=20 >=20>=20=20 >=20>=20 >=20> diff --git a/drivers/acpi/numa/hmat.c b/drivers/acpi/numa/hmat.c > >=20 >=20> index 2c8ccc91ebe6..a2f9e7a4b479 100644 > >=20 >=20> --- a/drivers/acpi/numa/hmat.c > >=20 >=20> +++ b/drivers/acpi/numa/hmat.c > >=20 >=20> @@ -940,10 +940,7 @@ static int hmat_set_default_dram_perf(void) > >=20 >=20> struct memory_target *target; > >=20 >=20> struct access_coordinate *attrs; > >=20 >=20>=20=20 >=20>=20 >=20> - if (!default_dram_type) > >=20 >=20> - return -EIO; > >=20 >=20> - > >=20 >=20> - for_each_node_mask(nid, default_dram_type->nodes) { > >=20 >=20> + for_each_node_mask(nid, default_dram_nodes) { > >=20 >=20 > As below. Do we care if the combination of RAM + CPU wasn't true >=20 >=20earlier and is true by this point? If not, why not just >=20 >=20compute the node mask in here and not store it. >=20 It=20makes sense to me. I think we can move the computation to here and remove the global node mask. > >=20 >=20> pxm =3D node_to_pxm(nid); > >=20 >=20> target =3D find_mem_target(pxm); > >=20 >=20> if (!target) > >=20 >=20> diff --git a/include/linux/memory-tiers.h b/include/linux/memory-t= iers.h > >=20 >=20> index 0d70788558f4..fa61ad9c4d75 100644 > >=20 >=20> --- a/include/linux/memory-tiers.h > >=20 >=20> +++ b/include/linux/memory-tiers.h > >=20 >=20> @@ -38,6 +38,7 @@ struct access_coordinate; > >=20 >=20> #ifdef CONFIG_NUMA > >=20 >=20> extern bool numa_demotion_enabled; > >=20 >=20> extern struct memory_dev_type *default_dram_type; > >=20 >=20> +extern nodemask_t default_dram_nodes __initdata; > >=20 >=20> struct memory_dev_type *alloc_memory_type(int adistance); > >=20 >=20> void put_memory_type(struct memory_dev_type *memtype); > >=20 >=20> void init_node_memory_type(int node, struct memory_dev_type *defau= lt_type); > >=20 >=20> @@ -76,6 +77,7 @@ static inline bool node_is_toptier(int node) > >=20 >=20>=20=20 >=20>=20 >=20> #define numa_demotion_enabled false > >=20 >=20> #define default_dram_type NULL > >=20 >=20> +#define default_dram_nodes NODE_MASK_NONE > >=20 >=20> /* > >=20 >=20> * CONFIG_NUMA implementation returns non NULL error. > >=20 >=20> */ > >=20 >=20> diff --git a/mm/memory-tiers.c b/mm/memory-tiers.c > >=20 >=20> index 6632102bd5c9..a19a90c3ad36 100644 > >=20 >=20> --- a/mm/memory-tiers.c > >=20 >=20> +++ b/mm/memory-tiers.c > >=20 >=20> @@ -43,6 +43,7 @@ static LIST_HEAD(memory_tiers); > >=20 >=20> static LIST_HEAD(default_memory_types); > >=20 >=20> static struct node_memory_type_map node_memory_types[MAX_NUMNODES]= ; > >=20 >=20> struct memory_dev_type *default_dram_type; > >=20 >=20> +nodemask_t default_dram_nodes __initdata =3D NODE_MASK_NONE; > >=20 >=20>=20=20 >=20>=20 >=20> static const struct bus_type memory_tier_subsys =3D { > >=20 >=20> .name =3D "memory_tiering", > >=20 >=20> @@ -671,28 +672,38 @@ EXPORT_SYMBOL_GPL(mt_put_memory_types); > >=20 >=20>=20=20 >=20>=20 >=20> /* > >=20 >=20> * This is invoked via `late_initcall()` to initialize memory tiers= for > >=20 >=20> - * CPU-less memory nodes after driver initialization, which is > >=20 >=20> - * expected to provide `adistance` algorithms. > >=20 >=20> + * memory nodes, both with and without CPUs. After the initializa= tion of > >=20 >=20> + * firmware and devices, adistance algorithms are expected to be = provided. > >=20 >=20> */ > >=20 >=20> static int __init memory_tier_late_init(void) > >=20 >=20> { > >=20 >=20> int nid; > >=20 >=20> + struct memory_tier *memtier; > >=20 >=20>=20=20 >=20>=20 >=20> + get_online_mems(); > >=20 >=20> guard(mutex)(&memory_tier_lock); > >=20 >=20> + /* > >=20 >=20> + * Look at all the existing and uninitialized N_MEMORY nodes and > >=20 >=20> + * add them to default memory tier or to a tier if we already hav= e > >=20 >=20> + * memory types assigned. > >=20 >=20> + */ > >=20 >=20> for_each_node_state(nid, N_MEMORY) { > >=20 >=20> /* > >=20 >=20> - * Some device drivers may have initialized memory tiers > >=20 >=20> - * between `memory_tier_init()` and `memory_tier_late_init()`, > >=20 >=20> - * potentially bringing online memory nodes and > >=20 >=20> - * configuring memory tiers. Exclude them here. > >=20 >=20> + * Some device drivers may have initialized > >=20 >=20> + * memory tiers, potentially bringing memory nodes > >=20 >=20> + * online and configuring memory tiers. > >=20 >=20> + * Exclude them here. > >=20 >=20> */ > >=20 >=20> if (node_memory_types[nid].memtype) > >=20 >=20> continue; > >=20 >=20>=20=20 >=20>=20 >=20> - set_node_memory_tier(nid); > >=20 >=20> + memtier =3D set_node_memory_tier(nid); > >=20 >=20> + if (IS_ERR(memtier)) > >=20 >=20> + /* Continue with memtiers we are able to setup. */ > >=20 >=20 > Might later ones be possible if we just continued this loop? >=20 I=20agree with you that theoretically, it=E2=80=99s possible for later attempts to succeed. I also agree that there is no harm in iterating through all possibilities. Therefore, we can do a continue here. Since it's legacy code. I would also like to hear Huang, Ying=E2=80=99s thoughts about this. > >=20 >=20> + break; > >=20 >=20> } > >=20 >=20> - > >=20 >=20 > White space was harmless - I'd leave it there rather than adding noise = to this diff. >=20 Thanks!=20Got it. I will roll it back in the v3. > >=20 >=20> establish_demotion_targets(); > >=20 >=20> + put_online_mems(); > >=20 >=20>=20=20 >=20>=20 >=20> return 0; > >=20 >=20> } > >=20 >=20> @@ -875,8 +886,7 @@ static int __meminit memtier_hotplug_callback(= struct notifier_block *self, > >=20 >=20>=20=20 >=20>=20 >=20> static int __init memory_tier_init(void) > >=20 >=20> { > >=20 >=20> - int ret, node; > >=20 >=20> - struct memory_tier *memtier; > >=20 >=20> + int ret; > >=20 >=20>=20=20 >=20>=20 >=20> ret =3D subsys_virtual_register(&memory_tier_subsys, NULL); > >=20 >=20> if (ret) > >=20 >=20> @@ -887,7 +897,8 @@ static int __init memory_tier_init(void) > >=20 >=20> GFP_KERNEL); > >=20 >=20> WARN_ON(!node_demotion); > >=20 >=20> #endif > >=20 >=20> - mutex_lock(&memory_tier_lock); > >=20 >=20> + > >=20 >=20> + guard(mutex)(&memory_tier_lock); > >=20 >=20 > If this was safe to do without the rest of the change (I think so) >=20 >=20then better to pull that out as a trivial precursor so less noise >=20 >=20in here. >=20 Do=20you mean instead of using guard(mutex)(), use mutex_lock() as it was? or? > >=20 >=20> /* > >=20 >=20> * For now we can have 4 faster memory tiers with smaller adistance > >=20 >=20> * than default DRAM tier. > >=20 >=20> @@ -897,29 +908,9 @@ static int __init memory_tier_init(void) > >=20 >=20> if (IS_ERR(default_dram_type)) > >=20 >=20> panic("%s() failed to allocate default DRAM tier\n", __func__); > >=20 >=20>=20=20 >=20>=20=0D > > - /* > >=20 >=20> - * Look at all the existing N_MEMORY nodes and add them to > >=20 >=20> - * default memory tier or to a tier if we already have memory > >=20 >=20> - * types assigned. > >=20 >=20> - */ > >=20 >=20> - for_each_node_state(node, N_MEMORY) { > >=20 >=20> - if (!node_state(node, N_CPU)) > >=20 >=20> - /* > >=20 >=20> - * Defer memory tier initialization on > >=20 >=20> - * CPUless numa nodes. These will be initialized > >=20 >=20> - * after firmware and devices are initialized. > >=20 >=20> - */ > >=20 >=20> - continue; > >=20 >=20> - > >=20 >=20> - memtier =3D set_node_memory_tier(node); > >=20 >=20> - if (IS_ERR(memtier)) > >=20 >=20> - /* > >=20 >=20> - * Continue with memtiers we are able to setup > >=20 >=20> - */ > >=20 >=20> - break; > >=20 >=20> - } > >=20 >=20> - establish_demotion_targets(); > >=20 >=20> - mutex_unlock(&memory_tier_lock); > >=20 >=20> + /* Record nodes with memory and CPU to set default DRAM performa= nce. */ > >=20 >=20> + nodes_and(default_dram_nodes, node_states[N_MEMORY], > >=20 >=20> + node_states[N_CPU]); > >=20 >=20 > There are systems where (for various esoteric reasons, such as describi= ng an >=20 >=20association with some other memory that isn't DRAM where the granular= ity >=20 >=20doesn't match) the CPU nodes contain no DRAM but rather it's one node= away. >=20 >=20Handling that can be a job for another day though. >=20 Thank=20you for informing me of this situation. Sounds like handling that also requires a mapping table between the CPU and the corresponding DRAM. > Why does this need to be computed here? Why not do it in >=20 >=20hmat_set_default_dram_perf? Doesn't seem to be used anywhere else. >=20 Replied=20above. > >=20 > > hotplug_memory_notifier(memtier_hotplug_callback, MEMTIER_HOTPLUG_PRI= ); > >=20 >=20> return 0; > > > -- Best Regards, Ho-Ren (Jack) Chuang