Re: solid state drive access and context switching

["Kyungmin Park" <kmpark@infradead.org>]

Hi,

On Dec 6, 2007 7:01 AM, Jared Hulbert <jaredeh@gmail.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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