+/** + * virBlkioWeightDeviceToStr: + * + * This function returns a string representing device weights that is + * suitable for writing to /cgroup/blkio/blkio.weight_device, given + * a list of weight devices. + */ +int virBlkioWeightDeviceToStr(virBlkioWeightDevicePtr weightdevices, + int ndevices, + char **result) +{ + int len = 0; + int ret = -1; + int i, j; + char **weight_devices; + char *str; + + if (VIR_ALLOC_N(weight_devices, ndevices) < 0) { + goto fail_nomem1; + } + for (i = 0; i < ndevices; i++) { + int tmp; + tmp = virAsprintf(&weight_devices[i], "%d:%d %d", + weightdevices[i].major, + weightdevices[i].minor, + weightdevices[i].weight); + if (tmp < 0) { + goto fail_nomem2; + } + len += tmp + 1; /* 1 for '\n' and the trailing '\0' */ + } + + if (VIR_ALLOC_N(str, len) < 0) { + goto fail_nomem2; + } + for (i = 0; i < ndevices; i++) { + strcat(str, weight_devices[i]); + strcat(str, "\n"); + } + str[len-1] = '\0'; + + *result = str; + + ret = 0; + +fail_nomem2: + for (j = 0; j < i; j++) + VIR_FREE(weight_devices[i]); + VIR_FREE(weight_devices); +fail_nomem1: + if (ret != 0) + virReportOOMError(); + return ret; +}
I think this method would become alot simpler if you switch over to use virBufferPtr for all the string concatenation and formatting.
Thanks, I'll look into this.
+ +/** + * virDomainBlkioWeightDeviceParseXML + * + * this function parses a XML node: + * + * <device> + * <major>major</major> + * <minor>minor</minor> + * <weight>weight</weight> + * </device> + * + * and fills a virBlkioWeightDevice struct. + */
I'm not really seeing the benefit in using major, minor in the XML for this. The <disk> element is using the /dev/hda1 path for the host device, so I'd expect the same path to be usable for the block I/O tuning.
How does the scope work here, does major,minor have to refer to a block device, or can it refer to a partition ? If we have multiple <device> elements, each giving a different partition on the same device can we set different weight for each partition ?
blkio doesn't support io control on a partition, so I add major, minor to refer to a block device as a whole, rather than utilizing the existing <disk> element. -- Thanks, Hu Tao