read perfomance patchset

Neil hello

if i am not mistaken here:

in first instance of : if(bi) ...
...

you return without setting to NULL

+static struct bio *remove_bio_from_retry(raid5_conf_t *conf)
+{
+ struct bio *bi;
+
+ bi = conf->retry_read_aligned;
+ if (bi) {
--> return bi;
--> conf->retry_read_aligned = NULL;
+ }
+ bi = conf->retry_read_aligned_list;
+ if(bi) {
+ conf->retry_read_aligned = bi->bi_next;
+ bi->bi_next = NULL;
+ bi->bi_phys_segments = 1; /* biased count of active stripes */
+ bi->bi_hw_segments = 0; /* count of processed stripes */
+ }
+
+ return bi;
+}

--
Raz
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Re: read perfomance patchset

On Monday June 19, raziebe@gmail.com wrote:
> Neil hello
>
> if i am not mistaken here:
>
> in first instance of : if(bi) ...
> ...
>
> you return without setting to NULL
>

Yes, you are right. Thanks.
And fixing that bug removes the crash.
However....

I've been doing a few tests and it is hard to measure much
improvement, which is strange.

I can maybe see a 1% improvement but that could just be noise.
I do some more and see if I can find out what is happening.

Interestingly, with a simple
dd if=/dev/md1 of=/dev/null bs=1024k
test, 2.6.16 is substantially faster (10%) than 2.6.17-rc6-mm2 before
that patches are added. There is something weird there.

Have you done any testing?

NeilBrown
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