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From: Jens Axboe <[email protected]>
To: Ammar Faizi <[email protected]>
Cc: Alviro Iskandar Setiawan <[email protected]>,
	Fernanda Ma'rouf <[email protected]>,
	Pavel Begunkov <[email protected]>,
	Hao Xu <[email protected]>,
	io-uring Mailing List <[email protected]>,
	GNU/Weeb Mailing List <[email protected]>
Subject: Re: [PATCH liburing v2 0/8] aarch64 support
Date: Mon, 4 Jul 2022 07:05:13 -0600	[thread overview]
Message-ID: <[email protected]> (raw)
In-Reply-To: <[email protected]>

On 7/4/22 6:52 AM, Ammar Faizi wrote:
> On 6/30/22 12:58 AM, Ammar Faizi wrote:
>> From: Ammar Faizi <[email protected]>
>>
>> Hi Jens,
>>
>> This is v2 revision of aarch64 support.
>>
>> This series contains nolibc support for aarch64 and one extra irrelevant
>> cleanup (patch #1). The missing bit from aarch64 is get_page_size()
>> which is a bit complicated to implement without libc.
>>
>> aarch64 supports three values of page size: 4K, 16K, and 64K which are
>> selected at kernel compilation time. Therefore, we can't hard code the
>> page size for this arch. In this series we utilize open(), read() and
>> close() syscall to find the page size from /proc/self/auxv.
>>
>> The auxiliary vector contains information about the page size, it is
>> located at `AT_PAGESZ` keyval pair.
> 
> This no longer applies, I will send v3 revision soon. If you have some
> comments, let me know so I can address it together with the rebase.

Just send a v3, didn't have time to go fully over it yet. One note,
though - for patch 5, I'd split get_page_size() into two pieces so you
just do:

static inline long get_page_size(void)
{
	static long cache_val;

	if (cache_val)
		return cache_val;

	return __get_page_size();
}

With that, we can have __get_page_size() just do that one thing, open
the file and read the value.

No need to init static variables to 0.

And finally, if the read/open/whatever fails in __get_page_size(),
assign cache_val to the fallback value as well. I don't see a point in
retrying the same operation later and expect a different result.

-- 
Jens Axboe


  reply	other threads:[~2022-07-04 13:06 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-06-29 17:58 [PATCH liburing v2 0/8] aarch64 support Ammar Faizi
2022-06-29 17:58 ` [PATCH liburing v2 1/8] CHANGELOG: Fixup missing space Ammar Faizi
2022-06-29 17:58 ` [PATCH liburing v2 2/8] arch: syscall: Add `__sys_open()` syscall Ammar Faizi
2022-06-29 17:58 ` [PATCH liburing v2 3/8] arch: syscall: Add `__sys_read()` syscall Ammar Faizi
2022-06-29 17:58 ` [PATCH liburing v2 4/8] arch: Remove `__INTERNAL__LIBURING_LIB_H` checks Ammar Faizi
2022-06-29 17:58 ` [PATCH liburing v2 5/8] arch/aarch64: lib: Add `get_page_size()` function Ammar Faizi
2022-06-29 17:58 ` [PATCH liburing v2 6/8] arch: Enable nolibc support for aarch64 Ammar Faizi
2022-06-29 17:58 ` [PATCH liburing v2 7/8] .github: Enable aarch64 nolibc build for GitHub bot Ammar Faizi
2022-06-29 17:58 ` [PATCH liburing v2 8/8] CHANGELOG: Note about aarch64 support Ammar Faizi
2022-07-04 12:52 ` [PATCH liburing v2 0/8] " Ammar Faizi
2022-07-04 13:05   ` Jens Axboe [this message]
2022-07-04 15:36     ` Ammar Faizi

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