lkml.org 
[lkml]   [2011]   [Jun]   [19]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    Date
    From
    Subject[PATCH 3/7] writeback: introduce smoothed global dirty limit
    The start of a heavy weight application (ie. KVM) may instantly knock
    down determine_dirtyable_memory() and hence the global/bdi dirty
    thresholds.

    So introduce global_dirty_limit for tracking the global dirty threshold
    with policies

    - follow downwards slowly
    - follow up in one shot

    global_dirty_limit can effectively mask out the impact of sudden drop of
    dirtyable memory. It will be used in the next patch for two new type of
    dirty limits.

    Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
    ---
    include/linux/writeback.h | 2 +
    mm/page-writeback.c | 41 ++++++++++++++++++++++++++++++++++++
    2 files changed, 43 insertions(+)

    --- linux-next.orig/include/linux/writeback.h 2011-06-19 22:56:18.000000000 +0800
    +++ linux-next/include/linux/writeback.h 2011-06-19 22:59:29.000000000 +0800
    @@ -88,6 +88,8 @@ static inline void laptop_sync_completio
    #endif
    void throttle_vm_writeout(gfp_t gfp_mask);

    +extern unsigned long global_dirty_limit;
    +
    /* These are exported to sysctl. */
    extern int dirty_background_ratio;
    extern unsigned long dirty_background_bytes;
    --- linux-next.orig/mm/page-writeback.c 2011-06-19 22:56:18.000000000 +0800
    +++ linux-next/mm/page-writeback.c 2011-06-19 22:59:29.000000000 +0800
    @@ -116,6 +116,7 @@ EXPORT_SYMBOL(laptop_mode);

    /* End of sysctl-exported parameters */

    +unsigned long global_dirty_limit;

    /*
    * Scale the writeback cache size proportional to the relative writeout speeds.
    @@ -510,6 +511,43 @@ static void bdi_update_write_bandwidth(s
    bdi->avg_write_bandwidth = avg;
    }

    +static void update_dirty_limit(unsigned long thresh,
    + unsigned long dirty)
    +{
    + unsigned long limit = global_dirty_limit;
    +
    + if (limit < thresh) {
    + limit = thresh;
    + goto update;
    + }
    +
    + if (limit > thresh &&
    + limit > dirty) {
    + limit -= (limit - max(thresh, dirty)) >> 5;
    + goto update;
    + }
    + return;
    +update:
    + global_dirty_limit = limit;
    +}
    +
    +static void global_update_bandwidth(unsigned long thresh,
    + unsigned long dirty,
    + unsigned long now)
    +{
    + static DEFINE_SPINLOCK(dirty_lock);
    +
    + if (now - default_backing_dev_info.bw_time_stamp < MAX_PAUSE)
    + return;
    +
    + spin_lock(&dirty_lock);
    + if (now - default_backing_dev_info.bw_time_stamp >= MAX_PAUSE) {
    + update_dirty_limit(thresh, dirty);
    + default_backing_dev_info.bw_time_stamp = now;
    + }
    + spin_unlock(&dirty_lock);
    +}
    +
    void __bdi_update_bandwidth(struct backing_dev_info *bdi,
    unsigned long thresh,
    unsigned long dirty,
    @@ -535,6 +573,9 @@ void __bdi_update_bandwidth(struct backi
    if (elapsed > HZ && time_before(bdi->bw_time_stamp, start_time))
    goto snapshot;

    + if (thresh)
    + global_update_bandwidth(thresh, dirty, now);
    +
    bdi_update_write_bandwidth(bdi, elapsed, written);

    snapshot:



    \
     
     \ /
      Last update: 2011-06-19 17:31    [W:0.032 / U:30.412 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site