About read/write requests in IO scheduler

About read/write requests in IO scheduler

[韩磊]

In IO scheduler level, whether all the read requests are synchronous?

Fwd: About read/write requests in IO scheduler

[韩磊]

---------- Forwarded message ----------
From: 韩磊 <bonben1989@gmail.com>
Date: 2013/11/10
Subject: About read/write requests in IO scheduler
To: Linux Kernel Mailing List <linux-kernel@vger.kernel.org>


In IO scheduler level, whether all the read requests are synchronous?

Re: About read/write requests in IO scheduler

[Jeff Moyer]

韩磊 <bonben1989@gmail.com> writes:

> In IO scheduler level, whether all the read requests are synchronous?

Generically, yes, I/O schedulers (and the whole block layer, in fact)
consider READs synchronous:

/*
 * We regard a request as sync, if either a read or a sync write
 */
static inline bool rw_is_sync(unsigned int rw_flags)
{
        return !(rw_flags & REQ_WRITE) || (rw_flags & REQ_SYNC);
}

Re: About read/write requests in IO scheduler

[韩磊]

Thank you very much!

2013/11/12 Jeff Moyer <jmoyer@redhat.com>:
> 韩磊 <bonben1989@gmail.com> writes:
>
>> In IO scheduler level, whether all the read requests are synchronous?
>
> Generically, yes, I/O schedulers (and the whole block layer, in fact)
> consider READs synchronous:
>
> /*
>  * We regard a request as sync, if either a read or a sync write
>  */
> static inline bool rw_is_sync(unsigned int rw_flags)
> {
>         return !(rw_flags & REQ_WRITE) || (rw_flags & REQ_SYNC);
> }