[libvirt] [PATCH 08.5/12] qemu: Create a set of macros to handle setting block iotune values
Erik Skultety
eskultet at redhat.com
Fri Sep 30 11:08:23 UTC 2016
On 30/09/16 12:57, John Ferlan wrote:
>
>
> On 09/30/2016 04:43 AM, Erik Skultety wrote:
>> On 28/09/16 22:27, John Ferlan wrote:
>>> Rework the code in a set of 3 macros that will use the "base" of
>>> 'bytes' or 'iops' and build up the prefixes of 'total_', 'read_',
>>> and 'write_' before adding the postfixes of '_sec', '_sec_max',
>>> and '_sec_max_length' and making the param->field comparison and
>>> adding of the field.
>>>
>>> Signed-off-by: John Ferlan <jferlan at redhat.com>
>>> ---
>>>
>>> NB: Hopefully this applies - my branch is based off of the git head
>>> which I refreshed prior to sending the patch
>>>
>>> Since I missed 2.3, I figured why not try to make the change.
>>>
>>> src/qemu/qemu_driver.c | 216 +++++++++++--------------------------------------
>>> 1 file changed, 45 insertions(+), 171 deletions(-)
>>>
>>> diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c
>>> index 2b5b6fc..cbf9483 100644
>>> --- a/src/qemu/qemu_driver.c
>>> +++ b/src/qemu/qemu_driver.c
>>> @@ -17321,6 +17321,41 @@ qemuDomainSetBlockIoTune(virDomainPtr dom,
>>> VIR_DOMAIN_TUNABLE_BLKDEV_DISK, path) < 0)
>>> goto endjob;
>>>
>>> +#define SET_IOTUNE_FIELD(FIELD, BOOL, CONST) \
>>> + do { \
>>> + info.FIELD = params->value.ul; \
>>> + BOOL = true; \
>>> + if (virTypedParamsAddULLong(&eventParams, &eventNparams, \
>>> + &eventMaxparams, \
>>> + VIR_DOMAIN_TUNABLE_BLKDEV_##CONST, \
>>> + param->value.ul) < 0) \
>>> + goto endjob; \
>>> + } while (0);
>>> +
>>
>> While I totally support ^^this kind of macro-based code cleanup,
>>
>
> Ironically it's what I started with, but still seeing:
>
> if (STREQ(param->field, VIR_DOMAIN_BLOCK_IOTUNE_TOTAL_BYTES_SEC))
> SET_IOTUNE_FIELD(total_bytes_sec, bytes, TOTAL_BYTES_SEC);
> else if (STREQ(param->field,
> VIR_DOMAIN_BLOCK_IOTUNE_READ_BYTES_SEC))
> SET_IOTUNE_FIELD(read_bytes_sec, bytes, READ_BYTES_SEC);
> else if (STREQ(param->field,
> VIR_DOMAIN_BLOCK_IOTUNE_WRITE_BYTES_SEC))
> SET_IOTUNE_FIELD(write_bytes_sec, bytes, WRITE_BYTES_SEC);
>
Yeah, I also posted some suggestion in my original reply, have a look at
that, to make it short I think that construction like this might work as
well and is still slightly more readable:
SET_IOTUNE_FIELD(total_bytes_sec, bytes, TOTAL_BYTES_SEC);
SET_IOTUNE_FIELD(read_bytes_sec, bytes, READ_BYTES_SEC);
SET_IOTUNE_FIELD(write_bytes_sec, bytes, WRITE_BYTES_SEC);
I purposely got rid of the if-else-if construction altogether because
the compiler might actually optimize it, as I said, see my original
reply to this patch and tell me what you think.
Erik
> felt like only a slight improvement to visibility. I agree what I ended
> up with I agree is overkill with respect to needing to stop, think, and
> map out what the macros do. I also know I went from if - else if - else
> if - else if (etc) to groups of 3 if - else if - else if. I was going to
> mention it, but figured it'd be somewhat obvious.
>
> But no harm in seeing what others thought - it's easy enough to go back
> to ^^this^^ version... BTW: eventually the SET_IOTUNE_FIELD spread
> across two lines especially with the _MAX_LENGTH parameters.
>
> Thanks for the feedback - I'll post a v2 in a little while...
>
> John
>
>>> +/* Taking a prefix build by CHECK_SET_IOTUNE, add the postfix of "_sec",
>>> + * "_sec_max", and "_sec_max_length" to each of the variables in order to
>>> + * in order to check each of the ways one of these can be used. The boolean
>>> + * doesn't care if "total_", "read_", or "write_" is the prefix. */
>>> +#define CHECK_IOTUNE(FIELD, BOOL, CONST) \
>>> + if (STREQ(param->field, VIR_DOMAIN_BLOCK_IOTUNE_##CONST##_SEC)) { \
>>> + SET_IOTUNE_FIELD(FIELD##_sec, set_##BOOL, CONST##_SEC); \
>>> + } else if (STREQ(param->field, \
>>> + VIR_DOMAIN_BLOCK_IOTUNE_##CONST##_SEC_MAX)) { \
>>> + SET_IOTUNE_FIELD(FIELD##_sec_max, set_##BOOL##_max, CONST##_SEC_MAX); \
>>> + } else if (STREQ(param->field, \
>>> + VIR_DOMAIN_BLOCK_IOTUNE_##CONST##_SEC_MAX_LENGTH)) { \
>>> + SET_IOTUNE_FIELD(FIELD##_sec_max_length, set_##BOOL##_max_length, \
>>> + CONST##_SEC_MAX_LENGTH); \
>>> + }
>>> +
>>> +/* For "bytes" and "tune", prepend the "total_", "read_", and "write_" onto
>>> + * the field/const names, but also passing the "base" field to be used as the
>>> + * basis of the boolean. */
>>> +#define CHECK_SET_IOTUNE(FIELD, CONST) \
>>> + CHECK_IOTUNE(total_##FIELD, FIELD, TOTAL_##CONST); \
>>> + CHECK_IOTUNE(read_##FIELD, FIELD, READ_##CONST); \
>>> + CHECK_IOTUNE(write_##FIELD, FIELD, WRITE_##CONST);
>>> +
>>
>> I'm rather skeptic about ^^this because IMHO it's just too much in terms
>> of code duplication cleanup. I think that in this case (like in many
>> other cases) we should try to find the sweet spot between line removal
>> and the time programmer spends reading these macros. We could use
>> exactly the same approach as we do with STORE_MEM_RECORD,
>> QEMU_ADD_NET_PARAM, PARSE_MEMTUNE_PARAM. Now, I know that in the
>> original hunk below was a massive if-else if block which compared to a
>> bunch of ifs like these:
>>
>> SET_IOTUNE_FIELD(ARG1,ARG2,ARG3);
>> SET_IOTUNE_FIELD(ARG1,ARG2,ARG3);
>> SET_IOTUNE_FIELD(ARG1,ARG2,ARG3);
>>
>> would prevent testing of any extra conditions once a single condition
>> has been satisfied. But I believe that, provided that param->field does
>> not change within any of the 'if' blocks (which it doesn't), the
>> compiler would optimize the two example hunks below and produce an
>> identical assembly for both.
>>
>> if (foo == 0)
>> bar0();
>> else if (foo == 1)
>> bar1();
>> else if (foo == 2)
>> bar2();
>> ##################
>> if (foo == 0)
>> bar0();
>> if (foo == 1)
>> bar1();
>> if (foo == 2)
>> bar2();
>>
>> Erik
>>
>>> for (i = 0; i < nparams; i++) {
>>> virTypedParameterPtr param = ¶ms[i];
>>>
>>> @@ -17331,178 +17366,17 @@ qemuDomainSetBlockIoTune(virDomainPtr dom,
>>> goto endjob;
>>> }
>>>
>>> - if (STREQ(param->field, VIR_DOMAIN_BLOCK_IOTUNE_TOTAL_BYTES_SEC)) {
>>> - info.total_bytes_sec = param->value.ul;
>>> - set_bytes = true;
>>> - if (virTypedParamsAddULLong(&eventParams, &eventNparams,
>>> - &eventMaxparams,
>>> - VIR_DOMAIN_TUNABLE_BLKDEV_TOTAL_BYTES_SEC,
>>> - param->value.ul) < 0)
>>> - goto endjob;
>>> - } else if (STREQ(param->field,
>>> - VIR_DOMAIN_BLOCK_IOTUNE_READ_BYTES_SEC)) {
>>> - info.read_bytes_sec = param->value.ul;
>>> - set_bytes = true;
>>> - if (virTypedParamsAddULLong(&eventParams, &eventNparams,
>>> - &eventMaxparams,
>>> - VIR_DOMAIN_TUNABLE_BLKDEV_READ_BYTES_SEC,
>>> - param->value.ul) < 0)
>>> - goto endjob;
>>> - } else if (STREQ(param->field,
>>> - VIR_DOMAIN_BLOCK_IOTUNE_WRITE_BYTES_SEC)) {
>>> - info.write_bytes_sec = param->value.ul;
>>> - set_bytes = true;
>>> - if (virTypedParamsAddULLong(&eventParams, &eventNparams,
>>> - &eventMaxparams,
>>> - VIR_DOMAIN_TUNABLE_BLKDEV_WRITE_BYTES_SEC,
>>> - param->value.ul) < 0)
>>> - goto endjob;
>>> - } else if (STREQ(param->field,
>>> - VIR_DOMAIN_BLOCK_IOTUNE_TOTAL_IOPS_SEC)) {
>>> - info.total_iops_sec = param->value.ul;
>>> - set_iops = true;
>>> - if (virTypedParamsAddULLong(&eventParams, &eventNparams,
>>> - &eventMaxparams,
>>> - VIR_DOMAIN_TUNABLE_BLKDEV_TOTAL_IOPS_SEC,
>>> - param->value.ul) < 0)
>>> - goto endjob;
>>> - } else if (STREQ(param->field,
>>> - VIR_DOMAIN_BLOCK_IOTUNE_READ_IOPS_SEC)) {
>>> - info.read_iops_sec = param->value.ul;
>>> - set_iops = true;
>>> - if (virTypedParamsAddULLong(&eventParams, &eventNparams,
>>> - &eventMaxparams,
>>> - VIR_DOMAIN_TUNABLE_BLKDEV_READ_IOPS_SEC,
>>> - param->value.ul) < 0)
>>> - goto endjob;
>>> - } else if (STREQ(param->field,
>>> - VIR_DOMAIN_BLOCK_IOTUNE_WRITE_IOPS_SEC)) {
>>> - info.write_iops_sec = param->value.ul;
>>> - set_iops = true;
>>> - if (virTypedParamsAddULLong(&eventParams, &eventNparams,
>>> - &eventMaxparams,
>>> - VIR_DOMAIN_TUNABLE_BLKDEV_WRITE_IOPS_SEC,
>>> - param->value.ul) < 0)
>>> - goto endjob;
>>> - } else if (STREQ(param->field,
>>> - VIR_DOMAIN_BLOCK_IOTUNE_TOTAL_BYTES_SEC_MAX)) {
>>> - info.total_bytes_sec_max = param->value.ul;
>>> - set_bytes_max = true;
>>> - if (virTypedParamsAddULLong(&eventParams, &eventNparams,
>>> - &eventMaxparams,
>>> - VIR_DOMAIN_TUNABLE_BLKDEV_TOTAL_BYTES_SEC_MAX,
>>> - param->value.ul) < 0)
>>> - goto endjob;
>>> - } else if (STREQ(param->field,
>>> - VIR_DOMAIN_BLOCK_IOTUNE_READ_BYTES_SEC_MAX)) {
>>> - info.read_bytes_sec_max = param->value.ul;
>>> - set_bytes_max = true;
>>> - if (virTypedParamsAddULLong(&eventParams, &eventNparams,
>>> - &eventMaxparams,
>>> - VIR_DOMAIN_TUNABLE_BLKDEV_READ_BYTES_SEC_MAX,
>>> - param->value.ul) < 0)
>>> - goto endjob;
>>> - } else if (STREQ(param->field,
>>> - VIR_DOMAIN_BLOCK_IOTUNE_WRITE_BYTES_SEC_MAX)) {
>>> - info.write_bytes_sec_max = param->value.ul;
>>> - set_bytes_max = true;
>>> - if (virTypedParamsAddULLong(&eventParams, &eventNparams,
>>> - &eventMaxparams,
>>> - VIR_DOMAIN_TUNABLE_BLKDEV_WRITE_BYTES_SEC_MAX,
>>> - param->value.ul) < 0)
>>> - goto endjob;
>>> - } else if (STREQ(param->field,
>>> - VIR_DOMAIN_BLOCK_IOTUNE_TOTAL_IOPS_SEC_MAX)) {
>>> - info.total_iops_sec_max = param->value.ul;
>>> - set_iops_max = true;
>>> - if (virTypedParamsAddULLong(&eventParams, &eventNparams,
>>> - &eventMaxparams,
>>> - VIR_DOMAIN_TUNABLE_BLKDEV_TOTAL_IOPS_SEC_MAX,
>>> - param->value.ul) < 0)
>>> - goto endjob;
>>> - } else if (STREQ(param->field,
>>> - VIR_DOMAIN_BLOCK_IOTUNE_READ_IOPS_SEC_MAX)) {
>>> - info.read_iops_sec_max = param->value.ul;
>>> - set_iops_max = true;
>>> - if (virTypedParamsAddULLong(&eventParams, &eventNparams,
>>> - &eventMaxparams,
>>> - VIR_DOMAIN_TUNABLE_BLKDEV_READ_IOPS_SEC_MAX,
>>> - param->value.ul) < 0)
>>> - goto endjob;
>>> - } else if (STREQ(param->field,
>>> - VIR_DOMAIN_BLOCK_IOTUNE_WRITE_IOPS_SEC_MAX)) {
>>> - info.write_iops_sec_max = param->value.ul;
>>> - set_iops_max = true;
>>> - if (virTypedParamsAddULLong(&eventParams, &eventNparams,
>>> - &eventMaxparams,
>>> - VIR_DOMAIN_TUNABLE_BLKDEV_WRITE_IOPS_SEC_MAX,
>>> - param->value.ul) < 0)
>>> - goto endjob;
>>> - } else if (STREQ(param->field,
>>> - VIR_DOMAIN_BLOCK_IOTUNE_SIZE_IOPS_SEC)) {
>>> - info.size_iops_sec = param->value.ul;
>>> - set_size_iops = true;
>>> - if (virTypedParamsAddULLong(&eventParams, &eventNparams,
>>> - &eventMaxparams,
>>> - VIR_DOMAIN_TUNABLE_BLKDEV_SIZE_IOPS_SEC,
>>> - param->value.ul) < 0)
>>> - goto endjob;
>>> - } else if (STREQ(param->field,
>>> - VIR_DOMAIN_BLOCK_IOTUNE_TOTAL_BYTES_SEC_MAX_LENGTH)) {
>>> - info.total_bytes_sec_max_length = param->value.ul;
>>> - set_bytes_max_length = true;
>>> - if (virTypedParamsAddULLong(&eventParams, &eventNparams,
>>> - &eventMaxparams,
>>> - VIR_DOMAIN_TUNABLE_BLKDEV_TOTAL_BYTES_SEC_MAX_LENGTH,
>>> - param->value.ul) < 0)
>>> - goto endjob;
>>> - } else if (STREQ(param->field,
>>> - VIR_DOMAIN_BLOCK_IOTUNE_READ_BYTES_SEC_MAX_LENGTH)) {
>>> - info.read_bytes_sec_max_length = param->value.ul;
>>> - set_bytes_max_length = true;
>>> - if (virTypedParamsAddULLong(&eventParams, &eventNparams,
>>> - &eventMaxparams,
>>> - VIR_DOMAIN_TUNABLE_BLKDEV_READ_BYTES_SEC_MAX_LENGTH,
>>> - param->value.ul) < 0)
>>> - goto endjob;
>>> - } else if (STREQ(param->field,
>>> - VIR_DOMAIN_BLOCK_IOTUNE_WRITE_BYTES_SEC_MAX_LENGTH)) {
>>> - info.write_bytes_sec_max_length = param->value.ul;
>>> - set_bytes_max_length = true;
>>> - if (virTypedParamsAddULLong(&eventParams, &eventNparams,
>>> - &eventMaxparams,
>>> - VIR_DOMAIN_TUNABLE_BLKDEV_WRITE_BYTES_SEC_MAX_LENGTH,
>>> - param->value.ul) < 0)
>>> - goto endjob;
>>> - } else if (STREQ(param->field,
>>> - VIR_DOMAIN_BLOCK_IOTUNE_TOTAL_IOPS_SEC_MAX_LENGTH)) {
>>> - info.total_iops_sec_max_length = param->value.ul;
>>> - set_iops_max_length = true;
>>> - if (virTypedParamsAddULLong(&eventParams, &eventNparams,
>>> - &eventMaxparams,
>>> - VIR_DOMAIN_TUNABLE_BLKDEV_TOTAL_IOPS_SEC_MAX_LENGTH,
>>> - param->value.ul) < 0)
>>> - goto endjob;
>>> - } else if (STREQ(param->field,
>>> - VIR_DOMAIN_BLOCK_IOTUNE_READ_IOPS_SEC_MAX_LENGTH)) {
>>> - info.read_iops_sec_max_length = param->value.ul;
>>> - set_iops_max_length = true;
>>> - if (virTypedParamsAddULLong(&eventParams, &eventNparams,
>>> - &eventMaxparams,
>>> - VIR_DOMAIN_TUNABLE_BLKDEV_READ_IOPS_SEC_MAX_LENGTH,
>>> - param->value.ul) < 0)
>>> - goto endjob;
>>> - } else if (STREQ(param->field,
>>> - VIR_DOMAIN_BLOCK_IOTUNE_WRITE_IOPS_SEC_MAX_LENGTH)) {
>>> - info.write_iops_sec_max_length = param->value.ul;
>>> - set_iops_max_length = true;
>>> - if (virTypedParamsAddULLong(&eventParams, &eventNparams,
>>> - &eventMaxparams,
>>> - VIR_DOMAIN_TUNABLE_BLKDEV_WRITE_IOPS_SEC_MAX_LENGTH,
>>> - param->value.ul) < 0)
>>> - goto endjob;
>>> - }
>>> + /* Use the macros to check the different fields that can be set for
>>> + * bytes and iops. In the end 18 different combinations are tried. */
>>> + CHECK_SET_IOTUNE(bytes, BYTES);
>>> + CHECK_SET_IOTUNE(iops, IOPS);
>>> + if (STREQ(param->field, VIR_DOMAIN_BLOCK_IOTUNE_SIZE_IOPS_SEC))
>>> + SET_IOTUNE_FIELD(size_iops_sec, set_size_iops, SIZE_IOPS_SEC);
>>> +
>>> }
>>> +#undef SET_IOTUNE_FIELD
>>> +#undef CHECK_IOTUNE
>>> +#undef CHECK_SET_IOTUNE
>>>
>>> if ((info.total_bytes_sec && info.read_bytes_sec) ||
>>> (info.total_bytes_sec && info.write_bytes_sec)) {
>>>
>>
>>
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