src/patches/suse-2.6.27.39/patches.arch/s390-17-perf-14-zfcp-optimize-qdio_account.patch

   1 From: Gerald Schaefer <geraldsc@de.ibm.com>
   2 Subject: [PATCH] zfcp: optimize zfcp_qdio_account
   3 References: bnc#532063,LTC#55526
   4
   5 From: Heiko Carstens <heiko.carstens@de.ibm.com>
   6
   7 Remove expensive ktime_get()/ktime_us_delta() functions from the hot
   8 path and use get_clock_monotonic() instead.
   9 This elimates seven function calls and avoids a lot of unnecessary
  10 calculations.
  11
  12 Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
  13
  14 Acked-by: John Jolly <jjolly@suse.de>
  15 ---
  16
  17  drivers/s390/scsi/zfcp_def.h  |    2 +-
  18  drivers/s390/scsi/zfcp_qdio.c |   11 +++++------
  19  2 files changed, 6 insertions(+), 7 deletions(-)
  20
  21 Index: linux-sles11/drivers/s390/scsi/zfcp_def.h
  22 ===================================================================
  23 --- linux-sles11.orig/drivers/s390/scsi/zfcp_def.h      2009-08-17 15:31:27.000000000 +0200
  24 +++ linux-sles11/drivers/s390/scsi/zfcp_def.h   2009-08-17 15:31:29.000000000 +0200
  25 @@ -472,7 +472,7 @@
  26         spinlock_t              req_q_lock;        /* for operations on queue */
  27         int                     req_q_pci_batch;   /* SBALs since PCI indication
  28                                                       was last set */
  29 -       ktime_t                 req_q_time; /* time of last fill level change */
  30 +       unsigned long long      req_q_time; /* time of last fill level change */
  31         u64                     req_q_util; /* for accounting */
  32         spinlock_t              qdio_stat_lock;
  33         u32                     fsf_req_seq_no;    /* FSF cmnd seq number */
  34 Index: linux-sles11/drivers/s390/scsi/zfcp_qdio.c
  35 ===================================================================
  36 --- linux-sles11.orig/drivers/s390/scsi/zfcp_qdio.c     2009-08-17 15:31:27.000000000 +0200
  37 +++ linux-sles11/drivers/s390/scsi/zfcp_qdio.c  2009-08-17 15:31:29.000000000 +0200
  38 @@ -77,16 +77,15 @@
  39  }
  40
  41  /* this needs to be called prior to updating the queue fill level */
  42 -static void zfcp_qdio_account(struct zfcp_adapter *adapter)
  43 +static inline void zfcp_qdio_account(struct zfcp_adapter *adapter)
  44  {
  45 -       ktime_t now;
  46 -       s64 span;
  47 +       unsigned long long now, span;
  48         int free, used;
  49
  50         spin_lock(&adapter->qdio_stat_lock);
  51 -       now = ktime_get();
  52 -       span = ktime_us_delta(now, adapter->req_q_time);
  53 -       free = max(0, atomic_read(&adapter->req_q.count));
  54 +       now = get_clock_monotonic();
  55 +       span = (now - adapter->req_q_time) >> 12;
  56 +       free = atomic_read(&adapter->req_q.count);
  57         used = QDIO_MAX_BUFFERS_PER_Q - free;
  58         adapter->req_q_util += used * span;
  59         adapter->req_q_time = now;