The percpu conversion allowed a straightforward handoff of stripe
processing to the async subsytem that initially showed some modest gains
(+4%). However, this model is too simplistic and leads to stripes
bouncing between raid5d and the async thread pool for every invocation
of handle_stripe(). As reported by Holger this can fall into a
pathological situation severely impacting throughput (6x performance
loss).
Revert this for now, to be resurrected once we have a more workable
thread pool.
Reported-by: Holger Kiehl <Holger.Kiehl@xxxxxx>
Signed-off-by: Dan Williams <dan.j.williams@xxxxxxxxx>
---
drivers/md/Kconfig | 11 -----------
drivers/md/raid5.c | 37 +++----------------------------------
2 files changed, 3 insertions(+), 45 deletions(-)
diff --git a/drivers/md/Kconfig b/drivers/md/Kconfig
index 2158377..f0fac58 100644
--- a/drivers/md/Kconfig
+++ b/drivers/md/Kconfig
@@ -154,17 +154,6 @@ config MD_RAID456
If unsure, say Y.
-config MULTICORE_RAID456
- bool "RAID-4/RAID-5/RAID-6 Multicore processing (EXPERIMENTAL)"
- depends on MD_RAID456
- depends on SMP
- depends on EXPERIMENTAL
- ---help---
- Enable the raid456 module to dispatch per-stripe raid operations to a
- thread pool.
-
- If unsure, say N.
-
config MD_RAID6_PQ
tristate
diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index c21cc50..11cdfe6 100644
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -47,7 +47,6 @@
#include <linux/kthread.h>
#include <linux/raid/pq.h>
#include <linux/async_tx.h>
-#include <linux/async.h>
#include <linux/seq_file.h>
#include <linux/cpu.h>
#include "md.h"
@@ -4349,36 +4348,6 @@ static int retry_aligned_read(raid5_conf_t *conf, struct bio *raid_bio)
return handled;
}
-#ifdef CONFIG_MULTICORE_RAID456
-static void __process_stripe(void *param, async_cookie_t cookie)
-{
- struct stripe_head *sh = param;
-
- handle_stripe(sh);
- release_stripe(sh);
-}
-
-static void process_stripe(struct stripe_head *sh, struct list_head *domain)
-{
- async_schedule_domain(__process_stripe, sh, domain);
-}
-
-static void synchronize_stripe_processing(struct list_head *domain)
-{
- async_synchronize_full_domain(domain);
-}
-#else
-static void process_stripe(struct stripe_head *sh, struct list_head *domain)
-{
- handle_stripe(sh);
- release_stripe(sh);
- cond_resched();
-}
-
-static void synchronize_stripe_processing(struct list_head *domain)
-{
-}
-#endif
/*
@@ -4393,7 +4362,6 @@ static void raid5d(mddev_t *mddev)
struct stripe_head *sh;
raid5_conf_t *conf = mddev->private;
int handled;
- LIST_HEAD(raid_domain);
pr_debug("+++ raid5d active\n");
@@ -4430,7 +4398,9 @@ static void raid5d(mddev_t *mddev)
spin_unlock_irq(&conf->device_lock);
handled++;
- process_stripe(sh, &raid_domain);
+ handle_stripe(sh);
+ release_stripe(sh);
+ cond_resched();
spin_lock_irq(&conf->device_lock);
}
@@ -4438,7 +4408,6 @@ static void raid5d(mddev_t *mddev)
spin_unlock_irq(&conf->device_lock);
- synchronize_stripe_processing(&raid_domain);
async_tx_issue_pending_all();
unplug_slaves(mddev);
--
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