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Re: [PATCH] Consolidate Linux readahead() implementations
On 23/09/2016 12:44, Yury Norov wrote:
> On Fri, Sep 23, 2016 at 11:24:32AM -0300, Adhemerval Zanella wrote:
>> On 23/09/2016 11:11, Yury Norov wrote:
>>> On Fri, Sep 23, 2016 at 10:32:35AM -0300, Adhemerval Zanella wrote:
>>>> Indeed, unfortunately tile seems to get its own readahead definition.
>>>> However I think it should not prevent us to use my previous strategy,
>>>> we can follow the SH example for pread (where it adds a dummy argument
>>>> before offset), and do something as:
>>>> #include <sysdep.h>
>>>> #ifndef _LP64
>>>> /* Although tile 32-bit ABI passed 64-bit arguments in even registers,
>>>> readahead interface does not follow this convention. */
>>>> # undef __ALIGNMENT_ARG
>>>> #include <sysdeps/unix/sysv/linux/readhead.c>
>>> Currently it looks like this to me (see below). If you think that separated file
>>> is better than new option - I'm OK with it, but I think it's strange because in
>>> other patches of series you introduce options (if I'm not mistake).
>> I prefer to not add any more __ASSUME macro until it is more general
>> and for this specific case (tile seems the only supported ABI that
>> implements readhead different than usual ABI).
>>> We also have 2 another implementations - in linux/wordsize-64/syscalls.list
>>> and linux/mips/mips64/n32/syscalls.list.
>>> I think wordsize-64 is safe to generalize, but I'm worry about mips64. If we'll
>>> choose adding new options and so having a single file, it seems, we'll have to
>>> add another option for mips64/n32, like this:
>> My understanding is mipc64n32 adds it on syscall list to avoid current
>> default Linux implementation where it splits the off64_t (since mips64n32
>> passes off64_t in only one register afaik). I think it is safe here,
>> since SYSCALL_LL64 for mips64n32 will correctly pass only one argument
>> instead of splitting it.
> OK. So for v2:
> - remove arm, mips, wordsize-64, powerpc implementations
> - generalize linux/readahead.c like below
> - add tile exception
> - remove all new __ASSUME
> If it's correct, I'll send new patch this evening or tomorrow.
That would be my recommendation.