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  1. 29 Dec, 2008 2 commits
  3. 09 Oct, 2008 3 commits
  5. 26 Jul, 2008 1 commit
  7. 03 Jul, 2008 1 commit
    • Jens Axboe's avatar
      as-iosched: properly protect ioc_gone and ioc count · 863fddcb
      Jens Axboe authored 
      
If we have multiple tasks freeing io contexts when as-iosched
is being unloaded, we could complete() ioc_gone twice. Fix that by
protecting ioc_gone complete() and clearing with a spinlock for
just that purpose. Doesn't matter from a performance perspective,
since it'll only enter that path when ioc_gone != NULL (when as-iosched
is being rmmod'ed).
Signed-off-by: default avatarJens Axboe <jens.axboe@oracle.com>
      863fddcb
  9. 01 Jul, 2008 1 commit
    • Divyesh Shah's avatar
      block: Fix the starving writes bug in the anticipatory IO scheduler · d585d0b9
      Divyesh Shah authored 
      
AS scheduler alternates between issuing read and write batches. It does
the batch switch only after all requests from the previous batch are
completed.

When switching to a write batch, if there is an on-going read request,
it waits for its completion and indicates its intention of switching by
setting ad->changed_batch and the new direction but does not update the
batch_expire_time for the new write batch which it does in the case of
no previous pending requests.
On completion of the read request, it sees that we were waiting for the
switch and schedules work for kblockd right away and resets the
ad->changed_data flag.
Now when kblockd enters dispatch_request where it is expected to pick
up a write request, it in turn ends the write batch because the
batch_expire_timer was not updated and shows the expire timestamp for
the previous batch.

This results in the write starvation for all the cases where there is
the intention for switching to a write batch, but there is a previous
in-flight read request and the batch gets reverted to a read_batch
right away.

This also holds true in the reverse case (switching from a write batch
to a read batch with an in-flight write request).

I've checked that this bug exists on 2.6.11, 2.6.18, 2.6.24 and
linux-2.6-block git HEAD. I've tested the fix on x86 platforms with
SCSI drives where the driver asks for the next request while a current
request is in-flight.

This patch is based off linux-2.6-block git HEAD.

Bug reproduction:
A simple scenario which reproduces this bug is:
- dd if=/dev/hda3 of=/dev/null &
- lilo
   The lilo takes forever to complete.

This can also be reproduced fairly easily with the earlier dd and
another test
program doing msync().

The example test program below should print out a message after every
iteration
but it simply hangs forever. With this bugfix it makes forward progress.

====
Example test program using msync() (thanks to suleiman AT google DOT
com)

inline uint64_t
rdtsc(void)
{
         int64_t tsc;

         __asm __volatile("rdtsc" : "=A" (tsc));
         return (tsc);
}

int
main(int argc, char **argv)
{
         struct stat st;
         uint64_t e, s, t;
         char *p, q;
         long i;
         int fd;

         if (argc < 2) {
                 printf("Usage: %s <file>\n", argv[0]);
                 return (1);
         }

         if ((fd = open(argv[1], O_RDWR | O_NOATIME)) < 0)
                 err(1, "open");

         if (fstat(fd, &st) < 0)
                 err(1, "fstat");

         p = mmap(NULL, st.st_size, PROT_READ | PROT_WRITE,
MAP_SHARED, fd, 0);

         t = 0;
         for (i = 0; i < 1000; i++) {
                 *p = 0;
                 msync(p, 4096, MS_SYNC);
                 s = rdtsc();
                *p = 0;
                 __asm __volatile(""::: "memory");
                 e = rdtsc();
                 if (argc > 2)
                         printf("%d: %lld cycles %jd %jd\n",
                                i, e - s, (intmax_t)s, (intmax_t)e);
                 t += e - s;
         }
         printf("average time: %lld cycles\n", t / 1000);
         return (0);
}

Cc: <stable@kernel.org>
Acked-by: default avatarNick Piggin <npiggin@suse.de>
Signed-off-by: default avatarJens Axboe <jens.axboe@oracle.com>
      d585d0b9
  11. 01 Feb, 2008 2 commits
    • Jens Axboe's avatar
      block: kill swap_io_context() · 3bc217ff
      Jens Axboe authored 
      
It blindly copies everything in the io_context, including the lock.
That doesn't work so well for either lock ordering or lockdep.

There seems zero point in swapping io contexts on a request to request
merge, so the best point of action is to just remove it.
Signed-off-by: default avatarJens Axboe <jens.axboe@oracle.com>
      3bc217ff
    • Jens Axboe's avatar
      as-iosched: fix inconsistent ioc->lock context · 8bdd3f8a
      Jens Axboe authored 
      
Since it's acquired from irq context, all locking must be of the
irq safe variant. Most are already inside the queue lock (which
already disables interrupts), but the io scheduler rmmod path
always has irqs enabled and the put_io_context() path may legally
be called with irqs enabled (even if it isn't usually). So fixup
those two.
Signed-off-by: default avatarJens Axboe <jens.axboe@oracle.com>
      8bdd3f8a
  13. 30 Jan, 2008 1 commit
  15. 28 Jan, 2008 1 commit
  17. 18 Dec, 2007 3 commits
  19. 24 Jul, 2007 1 commit
  21. 17 Jul, 2007 1 commit
  23. 09 May, 2007 1 commit
  25. 08 May, 2007 1 commit
  27. 13 Dec, 2006 1 commit
  29. 01 Dec, 2006 1 commit
  31. 22 Nov, 2006 1 commit
    • David Howells's avatar
      WorkStruct: Pass the work_struct pointer instead of context data · 65f27f38
      David Howells authored 
      
Pass the work_struct pointer to the work function rather than context data.
The work function can use container_of() to work out the data.

For the cases where the container of the work_struct may go away the moment the
pending bit is cleared, it is made possible to defer the release of the
structure by deferring the clearing of the pending bit.

To make this work, an extra flag is introduced into the management side of the
work_struct.  This governs auto-release of the structure upon execution.

Ordinarily, the work queue executor would release the work_struct for further
scheduling or deallocation by clearing the pending bit prior to jumping to the
work function.  This means that, unless the driver makes some guarantee itself
that the work_struct won't go away, the work function may not access anything
else in the work_struct or its container lest they be deallocated..  This is a
problem if the auxiliary data is taken away (as done by the last patch).

However, if the pending bit is *not* cleared before jumping to the work
function, then the work function *may* access the work_struct and its container
with no problems.  But then the work function must itself release the
work_struct by calling work_release().

In most cases, automatic release is fine, so this is the default.  Special
initiators exist for the non-auto-release case (ending in _NAR).
Signed-Off-By: default avatarDavid Howells <dhowells@redhat.com>
      65f27f38
  33. 01 Oct, 2006 1 commit
  35. 30 Sep, 2006 12 commits
  37. 30 Jun, 2006 1 commit
  39. 26 Jun, 2006 1 commit
  41. 23 Jun, 2006 3 commits
    • Jens Axboe's avatar
      [PATCH] rbtree: support functions used by the io schedulers · dd67d051
      Jens Axboe authored 
      
They all duplicate macros to check for empty root and/or node, and
clearing a node. So put those in rbtree.h.
Signed-off-by: default avatarJens Axboe <axboe@suse.de>
      dd67d051
    • Jens Axboe's avatar
      [PATCH] Kill PF_SYNCWRITE flag · b31dc66a
      Jens Axboe authored 
      
A process flag to indicate whether we are doing sync io is incredibly
ugly. It also causes performance problems when one does a lot of async
io and then proceeds to sync it. Part of the io will go out as async,
and the other part as sync. This causes a disconnect between the
previously submitted io and the synced io. For io schedulers such as CFQ,
this will cause us lost merges and suboptimal behaviour in scheduling.

Remove PF_SYNCWRITE completely from the fsync/msync paths, and let
the O_DIRECT path just directly indicate that the writes are sync
by using WRITE_SYNC instead.
Signed-off-by: default avatarJens Axboe <axboe@suse.de>
      b31dc66a
    • Akinobu Mita's avatar
      [PATCH] iosched: use hlist for request hashtable · bae386f7
      Akinobu Mita authored 
      
Use hlist instead of list_head for request hashtable in deadline-iosched
and as-iosched. It also can remove the flag to know hashed or unhashed.
Signed-off-by: default avatarAkinobu Mita <mita@miraclelinux.com>
Signed-off-by: default avatarJens Axboe <axboe@suse.de>

 block/as-iosched.c       |   45 +++++++++++++++++++--------------------------
 block/deadline-iosched.c |   39 ++++++++++++++++-----------------------
 2 files changed, 35 insertions(+), 49 deletions(-)
      bae386f7