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Date: Fri, 30 Sep 2011 15:56:38 +0200
From: Michal Hocko <mhocko@...e.cz>
To: Johannes Weiner <jweiner@...hat.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
Mel Gorman <mgorman@...e.de>,
Christoph Hellwig <hch@...radead.org>,
Dave Chinner <david@...morbit.com>,
Wu Fengguang <fengguang.wu@...el.com>, Jan Kara <jack@...e.cz>,
Rik van Riel <riel@...hat.com>,
Minchan Kim <minchan.kim@...il.com>,
Chris Mason <chris.mason@...cle.com>,
Theodore Ts'o <tytso@....edu>,
Andreas Dilger <adilger.kernel@...ger.ca>,
Shaohua Li <shaohua.li@...el.com>, xfs@....sgi.com,
linux-btrfs@...r.kernel.org, linux-ext4@...r.kernel.org,
linux-mm@...ck.org, linux-fsdevel@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: Re: [patch 2/5] mm: writeback: cleanups in preparation for per-zone
dirty limits
On Fri 30-09-11 09:17:21, Johannes Weiner wrote:
> The next patch will introduce per-zone dirty limiting functions in
> addition to the traditional global dirty limiting.
>
> Rename determine_dirtyable_memory() to global_dirtyable_memory()
> before adding the zone-specific version, and fix up its documentation.
>
> Also, move the functions to determine the dirtyable memory and the
> function to calculate the dirty limit based on that together so that
> their relationship is more apparent and that they can be commented on
> as a group.
>
> Signed-off-by: Johannes Weiner <jweiner@...hat.com>
> Reviewed-by: Minchan Kim <minchan.kim@...il.com>
> Acked-by: Mel Gorman <mel@...e.de>
Reviewed-by: Michal Hocko <mhocko@...e.cz>
> ---
> mm/page-writeback.c | 92 +++++++++++++++++++++++++-------------------------
> 1 files changed, 46 insertions(+), 46 deletions(-)
>
> diff --git a/mm/page-writeback.c b/mm/page-writeback.c
> index c8acf8a..78604a6 100644
> --- a/mm/page-writeback.c
> +++ b/mm/page-writeback.c
> @@ -186,12 +186,12 @@ static unsigned long highmem_dirtyable_memory(unsigned long total)
> }
>
> /**
> - * determine_dirtyable_memory - amount of memory that may be used
> + * global_dirtyable_memory - number of globally dirtyable pages
> *
> - * Returns the numebr of pages that can currently be freed and used
> - * by the kernel for direct mappings.
> + * Returns the global number of pages potentially available for dirty
> + * page cache. This is the base value for the global dirty limits.
> */
> -static unsigned long determine_dirtyable_memory(void)
> +static unsigned long global_dirtyable_memory(void)
> {
> unsigned long x;
>
> @@ -205,6 +205,47 @@ static unsigned long determine_dirtyable_memory(void)
> }
>
> /*
> + * global_dirty_limits - background-writeback and dirty-throttling thresholds
> + *
> + * 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
> + * real-time tasks.
> + */
> +void global_dirty_limits(unsigned long *pbackground, unsigned long *pdirty)
> +{
> + unsigned long background;
> + unsigned long dirty;
> + unsigned long uninitialized_var(available_memory);
> + struct task_struct *tsk;
> +
> + if (!vm_dirty_bytes || !dirty_background_bytes)
> + available_memory = global_dirtyable_memory();
> +
> + if (vm_dirty_bytes)
> + dirty = DIV_ROUND_UP(vm_dirty_bytes, PAGE_SIZE);
> + else
> + dirty = (vm_dirty_ratio * available_memory) / 100;
> +
> + if (dirty_background_bytes)
> + background = DIV_ROUND_UP(dirty_background_bytes, PAGE_SIZE);
> + else
> + background = (dirty_background_ratio * available_memory) / 100;
> +
> + if (background >= dirty)
> + background = dirty / 2;
> + tsk = current;
> + if (tsk->flags & PF_LESS_THROTTLE || rt_task(tsk)) {
> + background += background / 4;
> + dirty += dirty / 4;
> + }
> + *pbackground = background;
> + *pdirty = dirty;
> + trace_global_dirty_state(background, dirty);
> +}
> +
> +/*
> * couple the period to the dirty_ratio:
> *
> * period/2 ~ roundup_pow_of_two(dirty limit)
> @@ -216,7 +257,7 @@ static int calc_period_shift(void)
> if (vm_dirty_bytes)
> dirty_total = vm_dirty_bytes / PAGE_SIZE;
> else
> - dirty_total = (vm_dirty_ratio * determine_dirtyable_memory()) /
> + dirty_total = (vm_dirty_ratio * global_dirtyable_memory()) /
> 100;
> return 2 + ilog2(dirty_total - 1);
> }
> @@ -416,47 +457,6 @@ static unsigned long hard_dirty_limit(unsigned long thresh)
> return max(thresh, global_dirty_limit);
> }
>
> -/*
> - * global_dirty_limits - background-writeback and dirty-throttling thresholds
> - *
> - * 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
> - * real-time tasks.
> - */
> -void global_dirty_limits(unsigned long *pbackground, unsigned long *pdirty)
> -{
> - unsigned long background;
> - unsigned long dirty;
> - unsigned long uninitialized_var(available_memory);
> - struct task_struct *tsk;
> -
> - if (!vm_dirty_bytes || !dirty_background_bytes)
> - available_memory = determine_dirtyable_memory();
> -
> - if (vm_dirty_bytes)
> - dirty = DIV_ROUND_UP(vm_dirty_bytes, PAGE_SIZE);
> - else
> - dirty = (vm_dirty_ratio * available_memory) / 100;
> -
> - if (dirty_background_bytes)
> - background = DIV_ROUND_UP(dirty_background_bytes, PAGE_SIZE);
> - else
> - background = (dirty_background_ratio * available_memory) / 100;
> -
> - if (background >= dirty)
> - background = dirty / 2;
> - tsk = current;
> - if (tsk->flags & PF_LESS_THROTTLE || rt_task(tsk)) {
> - background += background / 4;
> - dirty += dirty / 4;
> - }
> - *pbackground = background;
> - *pdirty = dirty;
> - trace_global_dirty_state(background, dirty);
> -}
> -
> /**
> * bdi_dirty_limit - @bdi's share of dirty throttling threshold
> * @bdi: the backing_dev_info to query
> --
> 1.7.6.2
>
> --
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--
Michal Hocko
SUSE Labs
SUSE LINUX s.r.o.
Lihovarska 1060/12
190 00 Praha 9
Czech Republic
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