linux-kernel - Re: solid state drive access and context switching

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Message-ID: <9c9fda240712051951w28aae15dle08279f8cc329e95@mail.gmail.com>
Date:	Thu, 6 Dec 2007 12:51:31 +0900
From:	"Kyungmin Park" <kmpark@...radead.org>
To:	"Jared Hulbert" <jaredeh@...il.com>
Cc:	"Alan Cox" <alan@...rguk.ukuu.org.uk>,
	"Chris Friesen" <cfriesen@...tel.com>, linux-kernel@...r.kernel.org
Subject: Re: solid state drive access and context switching

Hi,

On Dec 6, 2007 7:01 AM, Jared Hulbert <jaredeh@...il.com> wrote:
> > Probably about 1000 clocks but its always going to depend upon the
> > workload and whether any other work can be done usefully.
>
> Yeah.  Sounds right, in the microsecond range.  Be interesting to see data.
>
> Anybody have ideas on what kind of experiments could confirm this
> estimate is right?

Is it the right place to write synchronously?
Now only concern the SATA.

Thank you,
Kyungmin Park

diff --git a/block/ll_rw_blk.c b/block/ll_rw_blk.c
index 3b927be..cce0618 100644
--- a/block/ll_rw_blk.c
+++ b/block/ll_rw_blk.c
@@ -3221,6 +3221,13 @@ static inline void __generic_make_request(struct bio *bio
        if (bio_check_eod(bio, nr_sectors))
                goto end_io;

+#if 1
+       /* FIXME simple hack */
+       if (MAJOR(bio->bi_bdev->bd_dev) == 8 && bio_data_dir(bio) == WRITE) {
+               /* WRITE_SYNC */
+               bio->bi_rw |= (1 << BIO_RW_SYNC);
+       }
+#endif
        /*
         * Resolve the mapping until finished. (drivers are
         * still free to implement/resolve their own stacking
--
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