SUSE/saptune

package note

import (
    "github.com/SUSE/saptune/sap"
    "github.com/SUSE/saptune/system"
    "github.com/SUSE/saptune/txtparser"
)

// LinuxPagingImprovements defines SAP Note 1557506
// 1557506 - Linux paging improvements
type LinuxPagingImprovements struct {
    PagingConfig string // configuration file for page cache, used by test cases and during optimise

    VMPagecacheLimitMB          uint64
    VMPagecacheLimitIgnoreDirty int
    UseAlgorithmForHANA         bool
}

// Name returns the name of the related SAP Note
func (paging LinuxPagingImprovements) Name() string {
    return "Linux paging improvements"
}

// Initialise reads the parameter values from current system
func (paging LinuxPagingImprovements) Initialise() (Note, error) {
    vmPagecach, _ := system.GetSysctlUint64(system.SysctlPagecacheLimitMB)
    vmIgnoreDirty, _ := system.GetSysctlInt(system.SysctlPagecacheLimitIgnoreDirty)
    return LinuxPagingImprovements{
        PagingConfig:                paging.PagingConfig,
        VMPagecacheLimitMB:          vmPagecach,
        VMPagecacheLimitIgnoreDirty: vmIgnoreDirty,
        UseAlgorithmForHANA:         true,
    }, nil
}

// Optimise gets the expected pagecache values from the configuration
// or calculates new values
func (paging LinuxPagingImprovements) Optimise() (Note, error) {
    newPaging := paging
    conf, err := txtparser.ParseSysconfigFile(newPaging.PagingConfig, false)
    if err != nil {
        return nil, err
    }
    inputEnable := conf.GetBool("ENABLE_PAGECACHE_LIMIT", false)
    inputOverride := conf.GetInt("OVERRIDE_PAGECACHE_LIMIT_MB", 0)

    // As discussed with SAP and Alliance team, use the HANA formula for
    // Netweaver too.
    // So for HANA and Netweaver: new limit is 2% system memory
    newPaging.VMPagecacheLimitMB = system.GetMainMemSizeMB() * 2 / 100
    if inputOverride != 0 {
        newPaging.VMPagecacheLimitMB = uint64(inputOverride)
    }
    if !inputEnable {
        newPaging.VMPagecacheLimitMB = 0
    }
    newPaging.VMPagecacheLimitIgnoreDirty = conf.GetInt(system.SysctlPagecacheLimitIgnoreDirty, 1)
    return newPaging, err
}

// Apply sets the new values in the system
func (paging LinuxPagingImprovements) Apply() error {
    errs := make([]error, 0)
    errs = append(errs, system.SetSysctlUint64(system.SysctlPagecacheLimitMB, paging.VMPagecacheLimitMB))
    errs = append(errs, system.SetSysctlInt(system.SysctlPagecacheLimitIgnoreDirty, paging.VMPagecacheLimitIgnoreDirty))

    err := sap.PrintErrors(errs)
    return err
}