The patch titled
Subject: mm: add /sys/class/bdi/<bdi>/min_bytes knob
has been added to the -mm mm-unstable branch. Its filename is
mm-add-sys-class-bdi-bdi-min_bytes-knob.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-add-sys-class-bdi-bdi-min_bytes-knob.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Stefan Roesch <shr@xxxxxxxxxxxx>
Subject: mm: add /sys/class/bdi/<bdi>/min_bytes knob
Date: Fri, 18 Nov 2022 16:52:08 -0800
bdi has two existing knobs to limit the amount of dirty memory:
min_ratio and max_ratio. However the granularity of the knobs is limited
and often it is more convenient to specify limits in terms of bytes.
This change adds the min_bytes knob.
It does not store the min_bytes value, instead it converts the max_bytes
value to a ratio. The value is therefore more an approximation than an
absolute value.
It also maintains the sum over all the bdi min_ratio values stored in
the variable bdi_min_ratio.
Link: https://lkml.kernel.org/r/20221119005215.3052436-14-shr@xxxxxxxxxxxx
Signed-off-by: Stefan Roesch <shr@xxxxxxxxxxxx>
Cc: Chris Mason <clm@xxxxxxxx>
Cc: Jens Axboe <axboe@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/backing-dev.c | 29 +++++++++++++++++++++++++++++
1 file changed, 29 insertions(+)
--- a/mm/backing-dev.c~mm-add-sys-class-bdi-bdi-min_bytes-knob
+++ a/mm/backing-dev.c
@@ -199,6 +199,34 @@ static ssize_t max_ratio_store(struct de
}
BDI_SHOW(max_ratio, bdi->max_ratio / BDI_RATIO_SCALE)
+static ssize_t min_bytes_show(struct device *dev,
+ struct device_attribute *attr,
+ char *buf)
+{
+ struct backing_dev_info *bdi = dev_get_drvdata(dev);
+
+ return sysfs_emit(buf, "%llu\n", bdi_get_min_bytes(bdi));
+}
+
+static ssize_t min_bytes_store(struct device *dev,
+ struct device_attribute *attr, const char *buf, size_t count)
+{
+ struct backing_dev_info *bdi = dev_get_drvdata(dev);
+ u64 bytes;
+ ssize_t ret;
+
+ ret = kstrtoull(buf, 10, &bytes);
+ if (ret < 0)
+ return ret;
+
+ ret = bdi_set_min_bytes(bdi, bytes);
+ if (!ret)
+ ret = count;
+
+ return ret;
+}
+DEVICE_ATTR_RW(min_bytes);
+
static ssize_t max_bytes_show(struct device *dev,
struct device_attribute *attr,
char *buf)
@@ -269,6 +297,7 @@ static struct attribute *bdi_dev_attrs[]
&dev_attr_read_ahead_kb.attr,
&dev_attr_min_ratio.attr,
&dev_attr_max_ratio.attr,
+ &dev_attr_min_bytes.attr,
&dev_attr_max_bytes.attr,
&dev_attr_stable_pages_required.attr,
&dev_attr_strict_limit.attr,
_
Patches currently in -mm which might be from shr@xxxxxxxxxxxx are
mm-add-bdi_set_strict_limit-function.patch
mm-add-knob-sys-class-bdi-bdi-strict_limit.patch
mm-document-sys-class-bdi-bdi-strict_limit-knob.patch
mm-use-part-per-1000000-for-bdi-ratios.patch
mm-add-bdi_get_max_bytes-function.patch
mm-split-off-__bdi_set_max_ratio-function.patch
mm-add-bdi_set_max_bytes-function.patch
mm-add-knob-sys-class-bdi-bdi-max_bytes.patch
mm-document-sys-class-bdi-bdi-max_bytes-knob.patch
mm-add-bdi_get_min_bytes-function.patch
mm-split-off-__bdi_set_min_ratio-function.patch
mm-add-bdi_set_min_bytes-function.patch
mm-add-sys-class-bdi-bdi-min_bytes-knob.patch
mm-document-sys-class-bdi-bdi-min_bytes-knob.patch
mm-add-bdi_set_max_ratio_no_scale-function.patch
mm-add-sys-class-bdi-bdi-max_ratio_fine-knob.patch
mm-document-sys-class-bdi-bdi-max_ratio_fine-knob.patch
mm-add-bdi_set_min_ratio_no_scale-function.patch
mm-add-sys-class-bdi-bdi-min_ratio_fine-knob.patch
mm-document-sys-class-bdi-bdi-min_ratio_fine-knob.patch
