Re: [PATCH] tools/mm: Add madvise tool

[David Hildenbrand <david@redhat.com>]

On 05.09.25 12:24, Kiryl Shutsemau wrote:
> On Fri, Sep 05, 2025 at 12:19:11PM +0200, David Hildenbrand wrote:
>> On 04.09.25 19:57, kirill@shutemov.name wrote:
>>> From: Kiryl Shutsemau <kas@kernel.org>
>>>
>>> Add a simple tool that allows to issue an advice on a process or a file.
>>>
>>> It can be useful to experiment with effects of an advice on a workload
>>> without modifying the workload itself.
>>>
>>> Only supports advices available for process_madvise().
>>>
>>> Signed-off-by: Kiryl Shutsemau <kas@kernel.org>
>>> ---
>>
>>> +	if (pid) {
>>> +		struct iovec vec = {
>>> +			.iov_base = (void *)start,
>>> +			.iov_len = end - start,
>>> +		};
>>> +		ssize_t ret;
>>> +
>>> +		ret = process_madvise(fd, &vec, 1, advice, 0);
>>> +		if (ret < 0)
>>> +			perror("process_madvise"), exit(-1);
>>> +
>>> +		if ((unsigned long)ret != end - start)
>>> +			printf("Partial advice occurred. Stopped at %#lx\n", start + ret);
>>> +	} else {
>>> +		unsigned long addr, hpage_pmd_size;
>>> +		void *p;
>>> +		int ret;
>>> +
>>> +		hpage_pmd_size = read_pmd_pagesize();
>>> +		if (!hpage_pmd_size) {
>>> +			printf("Reading PMD pagesize failed");
>>> +			exit(-1);
>>> +		}
>>> +
>>> +		// Allocate virtual address space to align the target mmap to PMD size
>>> +		// Some advices require this.
>>
>> I assume the kernel coding-style applies to tools/ as well, so
>>
>> /*
>>   * ...
>>   */
> 
> I thought C99 comments are fine now, no? Like slab_common.c uses them.

Was there a recent discussion around that?

Coding style says "The preferred style for long (multi-line) comments is:"

slab_common.c seems to be the mostly the only thing in MM, for some 
weird reason (and it's even being inconsistent).

So please, just default to /* for MM stuff unless there is a pretty good 
reason not to.

-- 
Cheers

David / dhildenb