Re: bounce buffer usage

[Jens Axboe]

On Wed, Jan 09 2002, Randy.Dunlap wrote:
> | The results look very promising, although I'm a bit surprised that 2.5
> | is actually that much quicker :-)
> 
> I was too.  When I have the bounce accounting straightened out,
> I'll run each test multiple times.

Good

> | +++ mm/highmem.c
> | @@ -409,7 +409,9 @@
> |                         vfrom = kmap(from->bv_page) + from->bv_offset;
> |                         memcpy(vto, vfrom, to->bv_len);
> |                         kunmap(from->bv_page);
> | -               }
> | +                       bounced_write++;
> | +               } else
> | +                       bounced_read++;
> |         }
> |
> | Of course those are all bounces, not just (or only) swap bounces. Also
> | note that the above is not SMP safe.
> 
> Is this the only place that kstat (kernel_stat) counters
> are not SMP safe...?

Haven't looked at the other stats, the i/o stats are protected by the
queue_lock though.

-- 
Jens Axboe