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// SPDX-License-Identifier: GPL-3.0-or-later
package dmcache
import (
"bufio"
"bytes"
"errors"
"fmt"
"strconv"
"strings"
)
type dmCacheDevice struct {
name string
metaBlockSizeSectors int64
metaUsedBlocks int64
metaTotalBlocks int64
cacheBlockSizeSectors int64
cacheUsedBlocks int64
cacheTotalBlocks int64
readHits int64
readMisses int64
writeHits int64
writeMisses int64
demotionsBlocks int64
promotionsBlocks int64
dirtyBlocks int64
}
func (c *DmCache) collect() (map[string]int64, error) {
bs, err := c.exec.cacheStatus()
if err != nil {
return nil, err
}
mx := make(map[string]int64)
if err := c.collectCacheStatus(mx, bs); err != nil {
return nil, err
}
return mx, nil
}
func (c *DmCache) collectCacheStatus(mx map[string]int64, data []byte) error {
var devices []*dmCacheDevice
sc := bufio.NewScanner(bytes.NewReader(data))
for sc.Scan() {
line := strings.TrimSpace(sc.Text())
if line == "" {
continue
}
dev, err := parseDmsetupStatusLine(line)
if err != nil {
return fmt.Errorf("malformed dmsetup status line: %v ('%s')", err, line)
}
devices = append(devices, dev)
}
seen := make(map[string]bool)
for _, dev := range devices {
seen[dev.name] = true
if !c.devices[dev.name] {
c.devices[dev.name] = true
c.addDeviceCharts(dev.name)
}
px := fmt.Sprintf("dmcache_device_%s_", dev.name)
const sectorSize = 512
metaMul := dev.metaBlockSizeSectors * sectorSize
cacheMul := dev.cacheBlockSizeSectors * sectorSize
mx[px+"metadata_free_bytes"] = (dev.metaTotalBlocks - dev.metaUsedBlocks) * metaMul
mx[px+"metadata_used_bytes"] = dev.metaUsedBlocks * metaMul
mx[px+"cache_free_bytes"] = (dev.cacheTotalBlocks - dev.cacheUsedBlocks) * cacheMul
mx[px+"cache_used_bytes"] = dev.cacheUsedBlocks * cacheMul
mx[px+"read_hits"] = dev.readHits
mx[px+"read_misses"] = dev.readMisses
mx[px+"write_hits"] = dev.writeHits
mx[px+"write_misses"] = dev.writeMisses
mx[px+"demotions_bytes"] = dev.demotionsBlocks * cacheMul
mx[px+"promotions_bytes"] = dev.promotionsBlocks * cacheMul
mx[px+"dirty_bytes"] = dev.dirtyBlocks * cacheMul
}
for dev := range c.devices {
if !seen[dev] {
delete(c.devices, dev)
c.removeDeviceCharts(dev)
}
}
if len(devices) == 0 {
return errors.New("no dm-cache devices found")
}
return nil
}
func parseDmsetupStatusLine(line string) (*dmCacheDevice, error) {
// https://www.kernel.org/doc/html/next/admin-guide/device-mapper/cache.html#status
parts := strings.Fields(line)
if len(parts) < 15 {
return nil, fmt.Errorf("want at least 15 fields, got %d", len(parts))
}
var dev dmCacheDevice
var err error
for i, s := range parts {
switch i {
case 0:
dev.name = strings.TrimSuffix(parts[0], ":")
case 4:
dev.metaBlockSizeSectors, err = parseInt(s)
case 5:
dev.metaUsedBlocks, dev.metaTotalBlocks, err = parseUsedTotalBlocks(s)
case 6:
dev.cacheBlockSizeSectors, err = parseInt(s)
case 7:
dev.cacheUsedBlocks, dev.cacheTotalBlocks, err = parseUsedTotalBlocks(s)
case 8:
dev.readHits, err = parseInt(s)
case 9:
dev.readMisses, err = parseInt(s)
case 10:
dev.writeHits, err = parseInt(s)
case 11:
dev.writeMisses, err = parseInt(s)
case 12:
dev.demotionsBlocks, err = parseInt(s)
case 13:
dev.promotionsBlocks, err = parseInt(s)
case 14:
dev.dirtyBlocks, err = parseInt(s)
}
if err != nil {
return nil, fmt.Errorf("failed to parse %d field '%s': %v", i, s, err)
}
}
return &dev, nil
}
func parseUsedTotalBlocks(info string) (int64, int64, error) {
parts := strings.Split(info, "/")
if len(parts) != 2 {
return 0, 0, errors.New("expected used/total")
}
used, err := parseInt(parts[0])
if err != nil {
return 0, 0, err
}
total, err := parseInt(parts[1])
if err != nil {
return 0, 0, err
}
return used, total, nil
}
func parseInt(s string) (int64, error) {
return strconv.ParseInt(s, 10, 64)
}
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