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  1. 17 Sep, 2014 30 commits
  3. 15 Sep, 2014 4 commits
    • Linus Torvalds's avatar
      vfs: fix bad hashing of dentries · be2378cb
      Linus Torvalds authored 
      commit 99d263d4 upstream.

Josef Bacik found a performance regression between 3.2 and 3.10 and
narrowed it down to commit bfcfaa77 ("vfs: use 'unsigned long'
accesses for dcache name comparison and hashing"). He reports:

 "The test case is essentially

      for (i = 0; i < 1000000; i++)
              mkdir("a$i");

  On xfs on a fio card this goes at about 20k dir/sec with 3.2, and 12k
  dir/sec with 3.10.  This is because we spend waaaaay more time in
  __d_lookup on 3.10 than in 3.2.

  The new hashing function for strings is suboptimal for <
  sizeof(unsigned long) string names (and hell even > sizeof(unsigned
  long) string names that I've tested).  I broke out the old hashing
  function and the new one into a userspace helper to get real numbers
  and this is what I'm getting:

      Old hash table had 1000000 entries, 0 dupes, 0 max dupes
      New hash table had 12628 entries, 987372 dupes, 900 max dupes
      We had 11400 buckets with a p50 of 30 dupes, p90 of 240 dupes, p99 of 567 dupes for the new hash

  My test does the hash, and then does the d_hash into a integer pointer
  array the same size as the dentry hash table on my system, and then
  just increments the value at the address we got to see how many
  entries we overlap with.

  As you can see the old hash function ended up with all 1 million
  entries in their own bucket, whereas the new one they are only
  distributed among ~12.5k buckets, which is why we're using so much
  more CPU in __d_lookup".

The reason for this hash regression is two-fold:

 - On 64-bit architectures the down-mixing of the original 64-bit
   word-at-a-time hash into the final 32-bit hash value is very
   simplistic and suboptimal, and just adds the two 32-bit parts
   together.

   In particular, because there is no bit shuffling and the mixing
   boundary is also a byte boundary, similar character patterns in the
   low and high word easily end up just canceling each other out.

 - the old byte-at-a-time hash mixed each byte into the final hash as it
   hashed the path component name, resulting in the low bits of the hash
   generally being a good source of hash data.  That is not true for the
   word-at-a-time case, and the hash data is distributed among all the
   bits.

The fix is the same in both cases: do a better job of mixing the bits up
and using as much of the hash data as possible.  We already have the
"hash_32|64()" functions to do that.
Reported-by: default avatarJosef Bacik <jbacik@fb.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Chris Mason <clm@fb.com>
Cc: linux-fsdevel@vger.kernel.org
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: default avatarJiri Slaby <jslaby@suse.cz>
      be2378cb
    • Al Viro's avatar
      dcache.c: get rid of pointless macros · c9258b20
      Al Viro authored 
      commit 482db906 upstream.

D_HASH{MASK,BITS} are used once each, both in the same function (d_hash()).
At this point they are actively misguiding - they imply that values are
compiler constants, which is no longer true.
Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
Signed-off-by: default avatarJiri Slaby <jslaby@suse.cz>
      c9258b20
    • Thomas Gleixner's avatar
      futex: Unlock hb->lock in futex_wait_requeue_pi() error path · 70279f38
      Thomas Gleixner authored 
      commit 13c42c2f upstream.

futex_wait_requeue_pi() calls futex_wait_setup(). If
futex_wait_setup() succeeds it returns with hb->lock held and
preemption disabled. Now the sanity check after this does:

        if (match_futex(&q.key, &key2)) {
	   	ret = -EINVAL;
		goto out_put_keys;
	}

which releases the keys but does not release hb->lock.

So we happily return to user space with hb->lock held and therefor
preemption disabled.

Unlock hb->lock before taking the exit route.
Reported-by: default avatarDave "Trinity" Jones <davej@redhat.com>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Reviewed-by: default avatarDarren Hart <dvhart@linux.intel.com>
Reviewed-by: default avatarDavidlohr Bueso <dave@stgolabs.net>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: stable@vger.kernel.org
Link: http://lkml.kernel.org/r/alpine.DEB.2.10.1409112318500.4178@nanosSigned-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Signed-off-by: default avatarJiri Slaby <jslaby@suse.cz>
      70279f38
    • Theodore Ts'o's avatar
      ext4: fix BUG_ON in mb_free_blocks() · bbcd86fa
      Theodore Ts'o authored 
      commit c99d1e6e upstream.

If we suffer a block allocation failure (for example due to a memory
allocation failure), it's possible that we will call
ext4_discard_allocated_blocks() before we've actually allocated any
blocks.  In that case, fe_len and fe_start in ac->ac_f_ex will still
be zero, and this will result in mb_free_blocks(inode, e4b, 0, 0)
triggering the BUG_ON on mb_free_blocks():

	BUG_ON(last >= (sb->s_blocksize << 3));

Fix this by bailing out of ext4_discard_allocated_blocks() if fs_len
is zero.

Also fix a missing ext4_mb_unload_buddy() call in
ext4_discard_allocated_blocks().

Google-Bug-Id: 16844242

Fixes: 86f0afd4Signed-off-by: default avatarTheodore Ts'o <tytso@mit.edu>
Cc: stable@vger.kernel.org
Signed-off-by: default avatarJiri Slaby <jslaby@suse.cz>
      bbcd86fa
  5. 12 Sep, 2014 2 commits
    • Prarit Bhargava's avatar
      x86, cpu hotplug: Fix stack frame warning in check_irq_vectors_for_cpu_disable() · 66acfbf7
      Prarit Bhargava authored 
      commit 39424e89 upstream.

Further discussion here: http://marc.info/?l=linux-kernel&m=139073901101034&w=2

kbuild, 0day kernel build service, outputs the warning:

arch/x86/kernel/irq.c:333:1: warning: the frame size of 2056 bytes
is larger than 2048 bytes [-Wframe-larger-than=]

because check_irq_vectors_for_cpu_disable() allocates two cpumasks on the
stack.   Fix this by moving the two cpumasks to a global file context.
Reported-by: default avatarFengguang Wu <fengguang.wu@intel.com>
Tested-by: default avatarDavid Rientjes <rientjes@google.com>
Signed-off-by: default avatarPrarit Bhargava <prarit@redhat.com>
Link: http://lkml.kernel.org/r/1390915331-27375-1-git-send-email-prarit@redhat.com
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Michel Lespinasse <walken@google.com>
Cc: Seiji Aguchi <seiji.aguchi@hds.com>
Cc: Yang Zhang <yang.z.zhang@Intel.com>
Cc: Paul Gortmaker <paul.gortmaker@windriver.com>
Cc: Janet Morgan <janet.morgan@intel.com>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Ruiv Wang <ruiv.wang@gmail.com>
Cc: Gong Chen <gong.chen@linux.intel.com>
Cc: Yinghai Lu <yinghai@kernel.org>
Signed-off-by: default avatarH. Peter Anvin <hpa@linux.intel.com>
Signed-off-by: default avatarJiri Slaby <jslaby@suse.cz>
      66acfbf7
    • Prarit Bhargava's avatar
      x86: Add check for number of available vectors before CPU down · 26a01cb8
      Prarit Bhargava authored 
      commit da6139e4 upstream.

Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=64791

When a cpu is downed on a system, the irqs on the cpu are assigned to
other cpus.  It is possible, however, that when a cpu is downed there
aren't enough free vectors on the remaining cpus to account for the
vectors from the cpu that is being downed.

This results in an interesting "overflow" condition where irqs are
"assigned" to a CPU but are not handled.

For example, when downing cpus on a 1-64 logical processor system:

<snip>
[  232.021745] smpboot: CPU 61 is now offline
[  238.480275] smpboot: CPU 62 is now offline
[  245.991080] ------------[ cut here ]------------
[  245.996270] WARNING: CPU: 0 PID: 0 at net/sched/sch_generic.c:264 dev_watchdog+0x246/0x250()
[  246.005688] NETDEV WATCHDOG: p786p1 (ixgbe): transmit queue 0 timed out
[  246.013070] Modules linked in: lockd sunrpc iTCO_wdt iTCO_vendor_support sb_edac ixgbe microcode e1000e pcspkr joydev edac_core lpc_ich ioatdma ptp mdio mfd_core i2c_i801 dca pps_core i2c_core wmi acpi_cpufreq isci libsas scsi_transport_sas
[  246.037633] CPU: 0 PID: 0 Comm: swapper/0 Not tainted 3.12.0+ #14
[  246.044451] Hardware name: Intel Corporation S4600LH ........../SVRBD-ROW_T, BIOS SE5C600.86B.01.08.0003.022620131521 02/26/2013
[  246.057371]  0000000000000009 ffff88081fa03d40 ffffffff8164fbf6 ffff88081fa0ee48
[  246.065728]  ffff88081fa03d90 ffff88081fa03d80 ffffffff81054ecc ffff88081fa13040
[  246.074073]  0000000000000000 ffff88200cce0000 0000000000000040 0000000000000000
[  246.082430] Call Trace:
[  246.085174]  <IRQ>  [<ffffffff8164fbf6>] dump_stack+0x46/0x58
[  246.091633]  [<ffffffff81054ecc>] warn_slowpath_common+0x8c/0xc0
[  246.098352]  [<ffffffff81054fb6>] warn_slowpath_fmt+0x46/0x50
[  246.104786]  [<ffffffff815710d6>] dev_watchdog+0x246/0x250
[  246.110923]  [<ffffffff81570e90>] ? dev_deactivate_queue.constprop.31+0x80/0x80
[  246.119097]  [<ffffffff8106092a>] call_timer_fn+0x3a/0x110
[  246.125224]  [<ffffffff8106280f>] ? update_process_times+0x6f/0x80
[  246.132137]  [<ffffffff81570e90>] ? dev_deactivate_queue.constprop.31+0x80/0x80
[  246.140308]  [<ffffffff81061db0>] run_timer_softirq+0x1f0/0x2a0
[  246.146933]  [<ffffffff81059a80>] __do_softirq+0xe0/0x220
[  246.152976]  [<ffffffff8165fedc>] call_softirq+0x1c/0x30
[  246.158920]  [<ffffffff810045f5>] do_softirq+0x55/0x90
[  246.164670]  [<ffffffff81059d35>] irq_exit+0xa5/0xb0
[  246.170227]  [<ffffffff8166062a>] smp_apic_timer_interrupt+0x4a/0x60
[  246.177324]  [<ffffffff8165f40a>] apic_timer_interrupt+0x6a/0x70
[  246.184041]  <EOI>  [<ffffffff81505a1b>] ? cpuidle_enter_state+0x5b/0xe0
[  246.191559]  [<ffffffff81505a17>] ? cpuidle_enter_state+0x57/0xe0
[  246.198374]  [<ffffffff81505b5d>] cpuidle_idle_call+0xbd/0x200
[  246.204900]  [<ffffffff8100b7ae>] arch_cpu_idle+0xe/0x30
[  246.210846]  [<ffffffff810a47b0>] cpu_startup_entry+0xd0/0x250
[  246.217371]  [<ffffffff81646b47>] rest_init+0x77/0x80
[  246.223028]  [<ffffffff81d09e8e>] start_kernel+0x3ee/0x3fb
[  246.229165]  [<ffffffff81d0989f>] ? repair_env_string+0x5e/0x5e
[  246.235787]  [<ffffffff81d095a5>] x86_64_start_reservations+0x2a/0x2c
[  246.242990]  [<ffffffff81d0969f>] x86_64_start_kernel+0xf8/0xfc
[  246.249610] ---[ end trace fb74fdef54d79039 ]---
[  246.254807] ixgbe 0000:c2:00.0 p786p1: initiating reset due to tx timeout
[  246.262489] ixgbe 0000:c2:00.0 p786p1: Reset adapter
Last login: Mon Nov 11 08:35:14 from 10.18.17.119
[root@(none) ~]# [  246.792676] ixgbe 0000:c2:00.0 p786p1: detected SFP+: 5
[  249.231598] ixgbe 0000:c2:00.0 p786p1: NIC Link is Up 10 Gbps, Flow Control: RX/TX
[  246.792676] ixgbe 0000:c2:00.0 p786p1: detected SFP+: 5
[  249.231598] ixgbe 0000:c2:00.0 p786p1: NIC Link is Up 10 Gbps, Flow Control: RX/TX

(last lines keep repeating.  ixgbe driver is dead until module reload.)

If the downed cpu has more vectors than are free on the remaining cpus on the
system, it is possible that some vectors are "orphaned" even though they are
assigned to a cpu.  In this case, since the ixgbe driver had a watchdog, the
watchdog fired and notified that something was wrong.

This patch adds a function, check_vectors(), to compare the number of vectors
on the CPU going down and compares it to the number of vectors available on
the system.  If there aren't enough vectors for the CPU to go down, an
error is returned and propogated back to userspace.

v2: Do not need to look at percpu irqs
v3: Need to check affinity to prevent counting of MSIs in IOAPIC Lowest
    Priority Mode
v4: Additional changes suggested by Gong Chen.
v5/v6/v7/v8: Updated comment text
Signed-off-by: default avatarPrarit Bhargava <prarit@redhat.com>
Link: http://lkml.kernel.org/r/1389613861-3853-1-git-send-email-prarit@redhat.comReviewed-by: default avatarGong Chen <gong.chen@linux.intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Michel Lespinasse <walken@google.com>
Cc: Seiji Aguchi <seiji.aguchi@hds.com>
Cc: Yang Zhang <yang.z.zhang@Intel.com>
Cc: Paul Gortmaker <paul.gortmaker@windriver.com>
Cc: Janet Morgan <janet.morgan@intel.com>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Ruiv Wang <ruiv.wang@gmail.com>
Cc: Gong Chen <gong.chen@linux.intel.com>
Signed-off-by: default avatarH. Peter Anvin <hpa@linux.intel.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: default avatarJiri Slaby <jslaby@suse.cz>
      26a01cb8
  7. 09 Sep, 2014 2 commits
  9. 03 Sep, 2014 2 commits
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