lkml.org 
[lkml]   [2011]   [Jun]   [9]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    From
    Subject[PATCH 00/14] Swap-over-NBD without deadlocking v4r3
    Date
    Changelog since V3
    o Propogate pfmemalloc from packet fragment pages to skb (Neil)
    o Rebase to 3.0-rc2

    Changelog since V2
    o Document that __GFP_NOMEMALLOC overrides __GFP_MEMALLOC (Neil)
    o Use wait_event_interruptible (Neil)
    o Use !! when casting to bool to avoid any possibilitity of type
    truncation (Neil)
    o Nicer logic when using skb_pfmemalloc_protocol (Neil)

    Changelog since V1
    o Rebase on top of mmotm
    o Use atomic_t for memalloc_socks (David Miller)
    o Remove use of sk_memalloc_socks in vmscan (Neil Brown)
    o Check throttle within prepare_to_wait (Neil Brown)
    o Add statistics on throttling instead of printk

    Swapping over NBD is something that is technically possible but not
    often advised. While there are number of guides on the internet
    on how to configure it and nbd-client supports a -swap switch to
    "prevent deadlocks", the fact of the matter is a machine using NBD
    for swap can be locked up within minutes if swap is used intensively.

    The problem is that network block devices do not use mempools like
    normal block devices do. As the host cannot control where they receive
    packets from, they cannot reliably work out in advance how much memory
    they might need.

    Some years ago, Peter Ziljstra developed a series of patches that
    supported swap over an NFS that some distributions are carrying in
    their kernels. This patch series borrows very heavily from Peter's work
    to support swapping over NBD (the relatively straight-forward case)
    and uses throttling instead of dynamically resized memory reserves
    so the series is not too unwieldy for review.

    Patch 1 serialises access to min_free_kbytes. It's not strictly needed
    by this series but as the series cares about watermarks in
    general, it's a harmless fix. It could be merged independently.

    Patch 2 adds knowledge of the PFMEMALLOC reserves to SLAB and SLUB to
    preserve access to pages allocated under low memory situations
    to callers that are freeying memory.

    Patch 3 introduces __GFP_MEMALLOC to allow access to the PFMEMALLOC
    reserves without setting PFMEMALLOC.

    Patch 4 opens the possibility for softirqs to use PFMEMALLOC reserves
    for later use by network packet processing.

    Patch 5 ignores memory policies when ALLOC_NO_WATERMARKS is set.

    Patches 6-10 allows network processing to use PFMEMALLOC reserves when
    the socket has been marked as being used by the VM to clean
    pages. If packets are received and stored in pages that were
    allocated under low-memory situations and are unrelated to
    the VM, the packets are dropped.

    Patch 11 is a micro-optimisation to avoid a function call in the
    common case.

    Patch 12 tags NBD sockets as being SOCK_MEMALLOC so they can use
    PFMEMALLOC if necessary.

    Patch 13 notes that it is still possible for the PFMEMALLOC reserve
    to be depleted. To prevent this, direct reclaimers get
    throttled on a waitqueue if 50% of the PFMEMALLOC reserves are
    depleted. It is expected that kswapd and the direct reclaimers
    already running will clean enough pages for the low watermark
    to be reached and the throttled processes are woken up.

    Patch 14 adds a statistic to track how often processes get throttled

    Some basic performance testing was run using kernel builds, netperf
    on loopback for UDP and TCP, hackbench (pipes and sockets), iozone
    and sysbench. Each of them were expected to use the sl*b allocators
    reasonably heavily but there did not appear to be significant
    performance variances. Here is the results from netperf using
    slab as an example

    NETPERF UDP
    64 237.47 ( 0.00%) 237.34 (-0.05%)
    128 472.69 ( 0.00%) 465.96 (-1.44%)
    256 926.82 ( 0.00%) 948.40 ( 2.28%)
    1024 3260.08 ( 0.00%) 3266.50 ( 0.20%)
    2048 5535.11 ( 0.00%) 5453.55 (-1.50%)
    3312 7496.60 ( 0.00%)* 7574.44 ( 1.03%)
    1.12% 1.00%
    4096 8266.35 ( 0.00%)* 8240.06 (-0.32%)*
    1.18% 1.49%
    8192 11026.01 ( 0.00%) 11010.44 (-0.14%)
    16384 14653.98 ( 0.00%) 14666.97 ( 0.09%)
    MMTests Statistics: duration
    User/Sys Time Running Test (seconds) 2156.64 1873.27
    Total Elapsed Time (seconds) 2570.09 2234.10

    NETPERF TCP
    netperf-tcp tcp-swapnbd
    vanilla-slab v4r3-slab
    64 1250.76 ( 0.00%) 1256.52 ( 0.46%)
    128 2290.70 ( 0.00%) 2336.43 ( 1.96%)
    256 3668.42 ( 0.00%) 3751.17 ( 2.21%)
    1024 7214.33 ( 0.00%) 7237.23 ( 0.32%)
    2048 8230.01 ( 0.00%) 8280.02 ( 0.60%)
    3312 8634.95 ( 0.00%) 8758.62 ( 1.41%)
    4096 8851.18 ( 0.00%) 9045.88 ( 2.15%)
    8192 10067.59 ( 0.00%) 10263.30 ( 1.91%)
    16384 11523.26 ( 0.00%) 11654.78 ( 1.13%)
    MMTests Statistics: duration
    User/Sys Time Running Test (seconds) 1450.23 1389.8
    Total Elapsed Time (seconds) 1450.41 1390.35

    Here is the equivalent test for SLUB

    netperf-udp udp-swapnbd
    vanilla-slub v4r3-slub
    64 235.33 ( 0.00%) 237.80 ( 1.04%)
    128 465.92 ( 0.00%) 469.98 ( 0.86%)
    256 907.16 ( 0.00%) 907.58 ( 0.05%)
    1024 3240.25 ( 0.00%) 3255.56 ( 0.47%)
    2048 5564.87 ( 0.00%) 5446.46 (-2.17%)
    3312 7427.65 ( 0.00%)* 7650.00 ( 2.91%)
    1.33% 1.00%
    4096 8004.51 ( 0.00%)* 8132.79 ( 1.58%)*
    1.05% 1.21%
    8192 11079.60 ( 0.00%) 10927.09 (-1.40%)
    16384 14737.38 ( 0.00%) 15019.50 ( 1.88%)
    MMTests Statistics: duration
    User/Sys Time Running Test (seconds) 2056.21 2160.38
    Total Elapsed Time (seconds) 2426.09 2498.16

    NETPERF TCP
    netperf-tcp tcp-swapnbd
    vanilla-slub v4r3-slub
    64 1251.64 ( 0.00%) 1262.89 ( 0.89%)
    128 2289.88 ( 0.00%) 2332.94 ( 1.85%)
    256 3654.34 ( 0.00%) 3736.48 ( 2.20%)
    1024 7192.47 ( 0.00%) 7286.96 ( 1.30%)
    2048 8243.55 ( 0.00%) 8291.50 ( 0.58%)
    3312 8664.16 ( 0.00%) 8799.88 ( 1.54%)
    4096 8869.13 ( 0.00%) 9018.12 ( 1.65%)
    8192 10009.53 ( 0.00%) 10214.26 ( 2.00%)
    16384 11470.78 ( 0.00%) 11685.20 ( 1.83%)
    MMTests Statistics: duration
    User/Sys Time Running Test (seconds) 1368.28 1511.81
    Total Elapsed Time (seconds) 1370.33 1510.42

    Time to completion varied a lot but this can happen with netperf as
    it tries to find results within a sufficiently high confidence. There
    were some small gains and losses but they are close to the variances
    seen between kernel releases.

    For testing swap-over-NBD, a machine was booted with 2G of RAM with a
    swapfile backed by NBD. 8*NUM_CPU processes were started that create
    anonymous memory mappings and read them linearly in a loop. The total
    size of the mappings were 4*PHYSICAL_MEMORY to use swap heavily under
    memory pressure. Without the patches, the machine locks up within
    minutes and runs to completion with them applied.

    drivers/block/nbd.c | 7 +-
    include/linux/gfp.h | 13 ++-
    include/linux/mm_types.h | 8 ++
    include/linux/mmzone.h | 1 +
    include/linux/sched.h | 7 +
    include/linux/skbuff.h | 21 +++-
    include/linux/slub_def.h | 1 +
    include/linux/vm_event_item.h | 1 +
    include/net/sock.h | 19 +++
    include/trace/events/gfpflags.h | 1 +
    kernel/softirq.c | 3 +
    mm/page_alloc.c | 57 +++++++--
    mm/slab.c | 240 +++++++++++++++++++++++++++++++++------
    mm/slub.c | 35 +++++-
    mm/vmscan.c | 55 +++++++++
    mm/vmstat.c | 1 +
    net/core/dev.c | 48 +++++++-
    net/core/filter.c | 8 ++
    net/core/skbuff.c | 95 +++++++++++++---
    net/core/sock.c | 42 +++++++
    net/ipv4/tcp.c | 3 +-
    net/ipv4/tcp_output.c | 13 +-
    net/ipv6/tcp_ipv6.c | 12 ++-
    23 files changed, 604 insertions(+), 87 deletions(-)

    --
    1.7.3.4

    Mel Gorman (14):
    mm: Serialize access to min_free_kbytes
    mm: sl[au]b: Add knowledge of PFMEMALLOC reserve pages
    mm: Introduce __GFP_MEMALLOC to allow access to emergency reserves
    mm: allow PF_MEMALLOC from softirq context
    mm: Ignore mempolicies when using ALLOC_NO_WATERMARK
    net: Introduce sk_allocation() to allow addition of GFP flags
    depending on the individual socket
    netvm: Allow the use of __GFP_MEMALLOC by specific sockets
    netvm: Allow skb allocation to use PFMEMALLOC reserves
    netvm: Propagate page->pfmemalloc to skb
    netvm: Set PF_MEMALLOC as appropriate during SKB processing
    mm: Micro-optimise slab to avoid a function call
    nbd: Set SOCK_MEMALLOC for access to PFMEMALLOC reserves
    mm: Throttle direct reclaimers if PF_MEMALLOC reserves are low and
    swap is backed by network storage
    mm: Account for the number of times direct reclaimers get throttled

    drivers/block/nbd.c | 7 +-
    include/linux/gfp.h | 13 ++-
    include/linux/mm_types.h | 8 ++
    include/linux/mmzone.h | 1 +
    include/linux/sched.h | 7 +
    include/linux/skbuff.h | 21 +++-
    include/linux/slub_def.h | 1 +
    include/linux/vm_event_item.h | 1 +
    include/net/sock.h | 19 +++
    include/trace/events/gfpflags.h | 1 +
    kernel/softirq.c | 3 +
    mm/page_alloc.c | 57 +++++++--
    mm/slab.c | 240 +++++++++++++++++++++++++++++++++------
    mm/slub.c | 33 +++++-
    mm/vmscan.c | 55 +++++++++
    mm/vmstat.c | 1 +
    net/core/dev.c | 48 +++++++-
    net/core/filter.c | 8 ++
    net/core/skbuff.c | 95 +++++++++++++---
    net/core/sock.c | 42 +++++++
    net/ipv4/tcp.c | 3 +-
    net/ipv4/tcp_output.c | 13 +-
    net/ipv6/tcp_ipv6.c | 12 ++-
    23 files changed, 602 insertions(+), 87 deletions(-)

    --
    1.7.3.4



    \
     
     \ /
      Last update: 2011-06-09 10:05    [W:0.033 / U:60.540 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site