Reduce bqlock contention in binsfree

[cse_cem_gmail_com]

Summary

Only take 'olock' when needed for REMFREE.

Sponsored by: EMC / Isilon Storage Division

[kib]

This looks fine.

sys/kern/vfs_bio.c

996–997

It seems you do not need to evaluate olock if B_REMFREE flag is not set.

999–1001

Move olock calculation there.

[cse_cem_gmail_com]

Will fix.

sys/kern/vfs_bio.c

996–997

Sure. But it isn't expensive either:

bqlock(int qindex)
{

        if (qindex == QUEUE_DIRTY)
                return (struct mtx *)(&bqdirty);
        return (struct mtx *)(&bqclean);
}

999–1001

Ok.

[cse_cem_gmail_com]

Move olock calculation to only where it is needed.

[cse_cem_gmail_com]

Committed in r284719.