projects / people / pmueller / ipfire-2.x.git / blame
| Commit | Line | Data |
|---|---|---|
| 00e5a55c BS |
1 | From: Gerald Schaefer <geraldsc@de.ibm.com> |
| 2 | Subject: kernel: disable cpu topology support by default | |
| 3 | References: bnc#450096,LTC#50392 | |
| 4 | ||
| 5 | Symptom: System performance may be lower than expected. | |
| 6 | Problem: If the hardware supports the configuration-topology facility | |
| 7 | the system cpu topology information will be passed to the | |
| 8 | scheduler. The scheduler bases its load balancing decisions | |
| 9 | also on the cpu topology. This may have a negative performance | |
| 10 | impact on machines where I/O interrupts are distributed unevenly | |
| 11 | to cpus. Those cpus which are grouped together and get more I/O | |
| 12 | interrupts than others will tend to have a higher average load. | |
| 13 | Solution: Disable cpu topology support by default and add a kernel parameter | |
| 14 | which allows to switch it on. In order to switch support on | |
| 15 | topology=on needs to be added to the kernel parameter line. | |
| 16 | ||
| 17 | Acked-by: John Jolly <jjolly@suse.de> | |
| 18 | --- | |
| 19 | Documentation/kernel-parameters.txt | 8 ++++++++ | |
| 20 | arch/s390/kernel/topology.c | 12 +++++++++++- | |
| 21 | 2 files changed, 19 insertions(+), 1 deletion(-) | |
| 22 | ||
| 23 | --- a/arch/s390/kernel/topology.c | |
| 24 | +++ b/arch/s390/kernel/topology.c | |
| 25 | @@ -59,6 +59,7 @@ struct core_info { | |
| 26 | cpumask_t mask; | |
| 27 | }; | |
| 28 | ||
| 29 | +static int topology_enabled; | |
| 30 | static void topology_work_fn(struct work_struct *work); | |
| 31 | static struct tl_info *tl_info; | |
| 32 | static struct core_info core_info; | |
| 33 | @@ -79,7 +80,7 @@ cpumask_t cpu_coregroup_map(unsigned int | |
| 34 | cpumask_t mask; | |
| 35 | ||
| 36 | cpus_clear(mask); | |
| 37 | - if (!machine_has_topology) | |
| 38 | + if (!topology_enabled || !machine_has_topology) | |
| 39 | return cpu_present_map; | |
| 40 | spin_lock_irqsave(&topology_lock, flags); | |
| 41 | while (core) { | |
| 42 | @@ -264,6 +265,15 @@ static void topology_interrupt(__u16 cod | |
| 43 | schedule_work(&topology_work); | |
| 44 | } | |
| 45 | ||
| 46 | +static int __init early_parse_topology(char *p) | |
| 47 | +{ | |
| 48 | + if (strncmp(p, "on", 2)) | |
| 49 | + return 0; | |
| 50 | + topology_enabled = 1; | |
| 51 | + return 0; | |
| 52 | +} | |
| 53 | +early_param("topology", early_parse_topology); | |
| 54 | + | |
| 55 | static int __init init_topology_update(void) | |
| 56 | { | |
| 57 | int rc; | |
| 58 | --- a/Documentation/kernel-parameters.txt | |
| 59 | +++ b/Documentation/kernel-parameters.txt | |
| 60 | @@ -2194,6 +2194,14 @@ and is between 256 and 4096 characters. | |
| 61 | See comment before function dc390_setup() in | |
| 62 | drivers/scsi/tmscsim.c. | |
| 63 | ||
| 64 | + topology= [S390] | |
| 65 | + Format: {off | on} | |
| 66 | + Specify if the kernel should make use of the cpu | |
| 67 | + topology informations if the hardware supports these. | |
| 68 | + The scheduler will make use of these informations and | |
| 69 | + e.g. base its process migration decisions on it. | |
| 70 | + Default is off. | |
| 71 | + | |
| 72 | tp720= [HW,PS2] | |
| 73 | ||
| 74 | trix= [HW,OSS] MediaTrix AudioTrix Pro |