zfs-patches/0053-Fix-MMP-write-frequency-for-large-pools.patch

   1 From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
   2 From: Brian Behlendorf <behlendorf1@llnl.gov>
   3 Date: Mon, 12 Mar 2018 11:26:05 -0700
   4 Subject: [PATCH] Fix MMP write frequency for large pools
   5 MIME-Version: 1.0
   6 Content-Type: text/plain; charset=UTF-8
   7 Content-Transfer-Encoding: 8bit
   8
   9 When a single pool contains more vdevs than the CONFIG_HZ for
  10 for the kernel the mmp thread will not delay properly.  Switch
  11 to using cv_timedwait_sig_hires() to handle higher resolution
  12 delays.
  13
  14 This issue was reported on Arch Linux where HZ defaults to only
  15 100 and this could be fairly easily reproduced with a reasonably
  16 large pool.  Most distribution kernels set CONFIG_HZ=250 or
  17 CONFIG_HZ=1000 and thus are unlikely to be impacted.
  18
  19 Reviewed-by: George Melikov <mail@gmelikov.ru>
  20 Reviewed-by: Giuseppe Di Natale <dinatale2@llnl.gov>
  21 Reviewed-by: Olaf Faaland <faaland1@llnl.gov>
  22 Reviewed-by: Tony Hutter <hutter2@llnl.gov>
  23 Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
  24 Closes #7205
  25 Closes #7289
  26 (cherry picked from commit c30e716c8149b7df7cf968373c22aa00b48d17b8)
  27 Signed-off-by: Fabian Grünbichler <f.gruenbichler@proxmox.com>
  28 ---
  29  lib/libspl/include/sys/time.h | 6 +++++-
  30  module/zfs/mmp.c              | 6 +++---
  31  2 files changed, 8 insertions(+), 4 deletions(-)
  32
  33 diff --git a/lib/libspl/include/sys/time.h b/lib/libspl/include/sys/time.h
  34 index f05fcaa1c..dc645fa5c 100644
  35 --- a/lib/libspl/include/sys/time.h
  36 +++ b/lib/libspl/include/sys/time.h
  37 @@ -54,10 +54,14 @@
  38  #define        MSEC2NSEC(m)    ((hrtime_t)(m) * (NANOSEC / MILLISEC))
  39  #endif
  40
  41 -#ifndef NSEC2MSEC
  42 +#ifndef        NSEC2MSEC
  43  #define        NSEC2MSEC(n)    ((n) / (NANOSEC / MILLISEC))
  44  #endif
  45
  46 +#ifndef USEC2NSEC
  47 +#define        USEC2NSEC(m)    ((hrtime_t)(m) * (NANOSEC / MICROSEC))
  48 +#endif
  49 +
  50  #ifndef        NSEC2SEC
  51  #define        NSEC2SEC(n)     ((n) / (NANOSEC / SEC))
  52  #endif
  53 diff --git a/module/zfs/mmp.c b/module/zfs/mmp.c
  54 index 15eea41ab..dc5c6a74f 100644
  55 --- a/module/zfs/mmp.c
  56 +++ b/module/zfs/mmp.c
  57 @@ -462,9 +462,9 @@ mmp_thread(spa_t *spa)
  58                         mmp_write_uberblock(spa);
  59
  60                 CALLB_CPR_SAFE_BEGIN(&cpr);
  61 -               (void) cv_timedwait_sig(&mmp->mmp_thread_cv,
  62 -                   &mmp->mmp_thread_lock, ddi_get_lbolt() +
  63 -                   ((next_time - gethrtime()) / (NANOSEC / hz)));
  64 +               (void) cv_timedwait_sig_hires(&mmp->mmp_thread_cv,
  65 +                   &mmp->mmp_thread_lock, next_time, USEC2NSEC(1),
  66 +                   CALLOUT_FLAG_ABSOLUTE);
  67                 CALLB_CPR_SAFE_END(&cpr, &mmp->mmp_thread_lock);
  68         }
  69
  70 --
  71 2.14.2
  72