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By design I left a tiny race in updating the I/O statistics based on

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the assumption that performance was more important that beancounter
quality statistics.

As it transpires the microoptimization is not measurable in the
real world and the inconsistent statistics confuse users, so revert
the decision.

MT6 candidate:	possibly
MT5 candidate:	possibly
This commit is contained in:
Poul-Henning Kamp 2005-07-25 21:12:54 +00:00
parent 50007d443b
commit 8827c821de
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=148410
1 changed files with 14 additions and 8 deletions
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22
sys/geom/geom_io.c
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@ -268,15 +268,18 @@ g_io_request(struct bio *bp, struct g_consumer *cp)
bp->bio_flags |= BIO_ONQUEUE;
binuptime(&bp->bio_t0);
if (g_collectstats & 4)
g_bioq_lock(&g_bio_run_down);
/*
* The statistics collection is lockless, as such, but we
* can not update one instance of the statistics from more
* than one thread at a time, so grab the lock first.
*/
g_bioq_lock(&g_bio_run_down);
if (g_collectstats & 1)
devstat_start_transaction(pp->stat, &bp->bio_t0);
if (g_collectstats & 2)
devstat_start_transaction(cp->stat, &bp->bio_t0);
if (!(g_collectstats & 4))
g_bioq_lock(&g_bio_run_down);
pp->nstart++;
cp->nstart++;
TAILQ_INSERT_TAIL(&g_bio_run_down.bio_queue, bp, bio_queue);
@ -322,14 +325,17 @@ g_io_deliver(struct bio *bp, int error)
bp->bio_bcount = bp->bio_length;
bp->bio_resid = bp->bio_bcount - bp->bio_completed;
if (g_collectstats & 4)
g_bioq_lock(&g_bio_run_up);
/*
* The statistics collection is lockless, as such, but we
* can not update one instance of the statistics from more
* than one thread at a time, so grab the lock first.
*/
g_bioq_lock(&g_bio_run_up);
if (g_collectstats & 1)
devstat_end_transaction_bio(pp->stat, bp);
if (g_collectstats & 2)
devstat_end_transaction_bio(cp->stat, bp);
if (!(g_collectstats & 4))
g_bioq_lock(&g_bio_run_up);
cp->nend++;
pp->nend++;
if (error != ENOMEM) {