Re: bounce buffer usage

Jens Axboe (axboe@suse.de)
Wed, 9 Jan 2002 19:10:22 +0100


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

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