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author | Tejun Heo <tj@kernel.org> | 2015-05-22 18:23:30 -0400 |
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committer | Jens Axboe <axboe@fb.com> | 2015-06-02 08:38:13 -0600 |
commit | 9fc3a43e1757ab6de0e8ce83b5d5a83083174e3b (patch) | |
tree | 01da652c433de8d4f2665c1b94ae012cd90df922 /mm/page-writeback.c | |
parent | c7981433ef05e67b1b40740b2c40edbd4476b659 (diff) | |
download | lwn-9fc3a43e1757ab6de0e8ce83b5d5a83083174e3b.tar.gz lwn-9fc3a43e1757ab6de0e8ce83b5d5a83083174e3b.zip |
writeback: separate out domain_dirty_limits()
global_dirty_limits() calculates thresh and bg_thresh (confusingly
called *pdirty and *pbackground in the function) assuming
global_wb_domain; however, cgroup writeback support requires
considering per-memcg wb_domain too.
This patch separates out domain_dirty_limits() which takes
dirty_throttle_control out of global_dirty_limits(). As thresh and
bg_thresh calculation needs the amount of dirtyable memory in the
domain, dirty_throttle_control->avail is added. The new function
calculates the two thresholds and store them directly in the
dirty_throttle_control.
Also, as memcg domains can't follow vm_dirty_bytes and
dirty_background_bytes settings directly. If those are set and
domain_dirty_limits() is invoked for a !global domain, the settings
are translated to ratios by scaling them against globally available
memory. dirty_throttle_control->gdtc is added to enable this when
CONFIG_CGROUP_WRITEBACK.
global_dirty_limits() is now a thin wrapper around
domain_dirty_limits() and balance_dirty_pages() is updated to use the
new function too.
This patch doesn't introduce any behavioral changes.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Jan Kara <jack@suse.cz>
Cc: Wu Fengguang <fengguang.wu@intel.com>
Cc: Greg Thelen <gthelen@google.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
Diffstat (limited to 'mm/page-writeback.c')
-rw-r--r-- | mm/page-writeback.c | 111 |
1 files changed, 86 insertions, 25 deletions
diff --git a/mm/page-writeback.c b/mm/page-writeback.c index a4d0ceefd097..c8ac8cea67dc 100644 --- a/mm/page-writeback.c +++ b/mm/page-writeback.c @@ -128,10 +128,12 @@ struct wb_domain global_wb_domain; struct dirty_throttle_control { #ifdef CONFIG_CGROUP_WRITEBACK struct wb_domain *dom; + struct dirty_throttle_control *gdtc; /* only set in memcg dtc's */ #endif struct bdi_writeback *wb; struct fprop_local_percpu *wb_completions; + unsigned long avail; /* dirtyable */ unsigned long dirty; /* file_dirty + write + nfs */ unsigned long thresh; /* dirty threshold */ unsigned long bg_thresh; /* dirty background threshold */ @@ -157,12 +159,18 @@ struct dirty_throttle_control { #define GDTC_INIT(__wb) .dom = &global_wb_domain, \ DTC_INIT_COMMON(__wb) +#define GDTC_INIT_NO_WB .dom = &global_wb_domain static struct wb_domain *dtc_dom(struct dirty_throttle_control *dtc) { return dtc->dom; } +static struct dirty_throttle_control *mdtc_gdtc(struct dirty_throttle_control *mdtc) +{ + return mdtc->gdtc; +} + static void wb_min_max_ratio(struct bdi_writeback *wb, unsigned long *minp, unsigned long *maxp) { @@ -193,12 +201,18 @@ static void wb_min_max_ratio(struct bdi_writeback *wb, #else /* CONFIG_CGROUP_WRITEBACK */ #define GDTC_INIT(__wb) DTC_INIT_COMMON(__wb) +#define GDTC_INIT_NO_WB static struct wb_domain *dtc_dom(struct dirty_throttle_control *dtc) { return &global_wb_domain; } +static struct dirty_throttle_control *mdtc_gdtc(struct dirty_throttle_control *mdtc) +{ + return NULL; +} + static void wb_min_max_ratio(struct bdi_writeback *wb, unsigned long *minp, unsigned long *maxp) { @@ -303,42 +317,88 @@ static unsigned long global_dirtyable_memory(void) return x + 1; /* Ensure that we never return 0 */ } -/* - * global_dirty_limits - background-writeback and dirty-throttling thresholds +/** + * domain_dirty_limits - calculate thresh and bg_thresh for a wb_domain + * @dtc: dirty_throttle_control of interest * - * Calculate the dirty thresholds based on sysctl parameters - * - vm.dirty_background_ratio or vm.dirty_background_bytes - * - vm.dirty_ratio or vm.dirty_bytes - * The dirty limits will be lifted by 1/4 for PF_LESS_THROTTLE (ie. nfsd) and + * Calculate @dtc->thresh and ->bg_thresh considering + * vm_dirty_{bytes|ratio} and dirty_background_{bytes|ratio}. The caller + * must ensure that @dtc->avail is set before calling this function. The + * dirty limits will be lifted by 1/4 for PF_LESS_THROTTLE (ie. nfsd) and * real-time tasks. */ -void global_dirty_limits(unsigned long *pbackground, unsigned long *pdirty) -{ - const unsigned long available_memory = global_dirtyable_memory(); - unsigned long background; - unsigned long dirty; +static void domain_dirty_limits(struct dirty_throttle_control *dtc) +{ + const unsigned long available_memory = dtc->avail; + struct dirty_throttle_control *gdtc = mdtc_gdtc(dtc); + unsigned long bytes = vm_dirty_bytes; + unsigned long bg_bytes = dirty_background_bytes; + unsigned long ratio = vm_dirty_ratio; + unsigned long bg_ratio = dirty_background_ratio; + unsigned long thresh; + unsigned long bg_thresh; struct task_struct *tsk; - if (vm_dirty_bytes) - dirty = DIV_ROUND_UP(vm_dirty_bytes, PAGE_SIZE); + /* gdtc is !NULL iff @dtc is for memcg domain */ + if (gdtc) { + unsigned long global_avail = gdtc->avail; + + /* + * The byte settings can't be applied directly to memcg + * domains. Convert them to ratios by scaling against + * globally available memory. + */ + if (bytes) + ratio = min(DIV_ROUND_UP(bytes, PAGE_SIZE) * 100 / + global_avail, 100UL); + if (bg_bytes) + bg_ratio = min(DIV_ROUND_UP(bg_bytes, PAGE_SIZE) * 100 / + global_avail, 100UL); + bytes = bg_bytes = 0; + } + + if (bytes) + thresh = DIV_ROUND_UP(bytes, PAGE_SIZE); else - dirty = (vm_dirty_ratio * available_memory) / 100; + thresh = (ratio * available_memory) / 100; - if (dirty_background_bytes) - background = DIV_ROUND_UP(dirty_background_bytes, PAGE_SIZE); + if (bg_bytes) + bg_thresh = DIV_ROUND_UP(bg_bytes, PAGE_SIZE); else - background = (dirty_background_ratio * available_memory) / 100; + bg_thresh = (bg_ratio * available_memory) / 100; - if (background >= dirty) - background = dirty / 2; + if (bg_thresh >= thresh) + bg_thresh = thresh / 2; tsk = current; if (tsk->flags & PF_LESS_THROTTLE || rt_task(tsk)) { - background += background / 4; - dirty += dirty / 4; + bg_thresh += bg_thresh / 4; + thresh += thresh / 4; } - *pbackground = background; - *pdirty = dirty; - trace_global_dirty_state(background, dirty); + dtc->thresh = thresh; + dtc->bg_thresh = bg_thresh; + + /* we should eventually report the domain in the TP */ + if (!gdtc) + trace_global_dirty_state(bg_thresh, thresh); +} + +/** + * global_dirty_limits - background-writeback and dirty-throttling thresholds + * @pbackground: out parameter for bg_thresh + * @pdirty: out parameter for thresh + * + * Calculate bg_thresh and thresh for global_wb_domain. See + * domain_dirty_limits() for details. + */ +void global_dirty_limits(unsigned long *pbackground, unsigned long *pdirty) +{ + struct dirty_throttle_control gdtc = { GDTC_INIT_NO_WB }; + + gdtc.avail = global_dirtyable_memory(); + domain_dirty_limits(&gdtc); + + *pbackground = gdtc.bg_thresh; + *pdirty = gdtc.thresh; } /** @@ -1421,9 +1481,10 @@ static void balance_dirty_pages(struct address_space *mapping, */ nr_reclaimable = global_page_state(NR_FILE_DIRTY) + global_page_state(NR_UNSTABLE_NFS); + gdtc->avail = global_dirtyable_memory(); gdtc->dirty = nr_reclaimable + global_page_state(NR_WRITEBACK); - global_dirty_limits(&gdtc->bg_thresh, &gdtc->thresh); + domain_dirty_limits(gdtc); if (unlikely(strictlimit)) { wb_dirty_limits(gdtc); |