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Date: Fri, 18 Jan 2019 11:31:27 +0100
From: Andrea Righi <righi.andrea@...il.com>
To: Tejun Heo <tj@...nel.org>, Li Zefan <lizefan@...wei.com>,
Johannes Weiner <hannes@...xchg.org>
Cc: Jens Axboe <axboe@...nel.dk>, Vivek Goyal <vgoyal@...hat.com>,
Josef Bacik <josef@...icpanda.com>,
Dennis Zhou <dennis@...nel.org>, cgroups@...r.kernel.org,
linux-block@...r.kernel.org, linux-kernel@...r.kernel.org,
Andrea Righi <righi.andrea@...il.com>
Subject: [RFC PATCH 3/3] fsio-throttle: instrumentation
Apply the fsio controller to the opportune kernel functions to evaluate
and throttle filesystem I/O.
Signed-off-by: Andrea Righi <righi.andrea@...il.com>
---
block/blk-core.c | 10 ++++++++++
include/linux/writeback.h | 7 ++++++-
mm/filemap.c | 20 +++++++++++++++++++-
mm/page-writeback.c | 14 ++++++++++++--
4 files changed, 47 insertions(+), 4 deletions(-)
diff --git a/block/blk-core.c b/block/blk-core.c
index 3c5f61ceeb67..4b4717f64ac1 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -16,6 +16,7 @@
#include <linux/backing-dev.h>
#include <linux/bio.h>
#include <linux/blkdev.h>
+#include <linux/fsio-throttle.h>
#include <linux/blk-mq.h>
#include <linux/highmem.h>
#include <linux/mm.h>
@@ -956,6 +957,15 @@ generic_make_request_checks(struct bio *bio)
*/
create_io_context(GFP_ATOMIC, q->node);
+ /*
+ * Account only READs at this layer (WRITEs are accounted and throttled
+ * in balance_dirty_pages()) and don't enfore sleeps (state=0): in this
+ * way we can prevent potential lock contentions and priority inversion
+ * problems at the filesystem layer.
+ */
+ if (bio_op(bio) == REQ_OP_READ)
+ fsio_throttle(bio_dev(bio), bio->bi_iter.bi_size, 0);
+
if (!blkcg_bio_issue_check(q, bio))
return false;
diff --git a/include/linux/writeback.h b/include/linux/writeback.h
index 738a0c24874f..1e161c7969e5 100644
--- a/include/linux/writeback.h
+++ b/include/linux/writeback.h
@@ -356,7 +356,12 @@ void global_dirty_limits(unsigned long *pbackground, unsigned long *pdirty);
unsigned long wb_calc_thresh(struct bdi_writeback *wb, unsigned long thresh);
void wb_update_bandwidth(struct bdi_writeback *wb, unsigned long start_time);
-void balance_dirty_pages_ratelimited(struct address_space *mapping);
+
+#define balance_dirty_pages_ratelimited(__mapping) \
+ __balance_dirty_pages_ratelimited(__mapping, false)
+void __balance_dirty_pages_ratelimited(struct address_space *mapping,
+ bool redirty);
+
bool wb_over_bg_thresh(struct bdi_writeback *wb);
typedef int (*writepage_t)(struct page *page, struct writeback_control *wbc,
diff --git a/mm/filemap.c b/mm/filemap.c
index 9f5e323e883e..5cc0959274d6 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -29,6 +29,7 @@
#include <linux/backing-dev.h>
#include <linux/pagevec.h>
#include <linux/blkdev.h>
+#include <linux/fsio-throttle.h>
#include <linux/security.h>
#include <linux/cpuset.h>
#include <linux/hugetlb.h>
@@ -2040,6 +2041,7 @@ static ssize_t generic_file_buffered_read(struct kiocb *iocb,
{
struct file *filp = iocb->ki_filp;
struct address_space *mapping = filp->f_mapping;
+ struct block_device *bdev = as_to_bdev(mapping);
struct inode *inode = mapping->host;
struct file_ra_state *ra = &filp->f_ra;
loff_t *ppos = &iocb->ki_pos;
@@ -2068,6 +2070,7 @@ static ssize_t generic_file_buffered_read(struct kiocb *iocb,
cond_resched();
find_page:
+ fsio_throttle(bdev_to_dev(bdev), 0, TASK_INTERRUPTIBLE);
if (fatal_signal_pending(current)) {
error = -EINTR;
goto out;
@@ -2308,11 +2311,17 @@ generic_file_read_iter(struct kiocb *iocb, struct iov_iter *iter)
if (iocb->ki_flags & IOCB_DIRECT) {
struct file *file = iocb->ki_filp;
struct address_space *mapping = file->f_mapping;
+ struct block_device *bdev = as_to_bdev(mapping);
struct inode *inode = mapping->host;
loff_t size;
size = i_size_read(inode);
if (iocb->ki_flags & IOCB_NOWAIT) {
+ unsigned long long sleep;
+
+ sleep = fsio_throttle(bdev_to_dev(bdev), 0, 0);
+ if (sleep)
+ return -EAGAIN;
if (filemap_range_has_page(mapping, iocb->ki_pos,
iocb->ki_pos + count - 1))
return -EAGAIN;
@@ -2322,6 +2331,7 @@ generic_file_read_iter(struct kiocb *iocb, struct iov_iter *iter)
iocb->ki_pos + count - 1);
if (retval < 0)
goto out;
+ fsio_throttle(bdev_to_dev(bdev), 0, TASK_INTERRUPTIBLE);
}
file_accessed(file);
@@ -2366,9 +2376,11 @@ EXPORT_SYMBOL(generic_file_read_iter);
static int page_cache_read(struct file *file, pgoff_t offset, gfp_t gfp_mask)
{
struct address_space *mapping = file->f_mapping;
+ struct block_device *bdev = as_to_bdev(mapping);
struct page *page;
int ret;
+ fsio_throttle(bdev_to_dev(bdev), 0, TASK_INTERRUPTIBLE);
do {
page = __page_cache_alloc(gfp_mask);
if (!page)
@@ -2498,11 +2510,15 @@ vm_fault_t filemap_fault(struct vm_fault *vmf)
*/
page = find_get_page(mapping, offset);
if (likely(page) && !(vmf->flags & FAULT_FLAG_TRIED)) {
+ struct block_device *bdev = as_to_bdev(mapping);
/*
* We found the page, so try async readahead before
* waiting for the lock.
*/
do_async_mmap_readahead(vmf->vma, ra, file, page, offset);
+ if (unlikely(!PageUptodate(page)))
+ fsio_throttle(bdev_to_dev(bdev), 0,
+ TASK_INTERRUPTIBLE);
} else if (!page) {
/* No page in the page cache at all */
do_sync_mmap_readahead(vmf->vma, ra, file, offset);
@@ -3172,6 +3188,7 @@ ssize_t generic_perform_write(struct file *file,
long status = 0;
ssize_t written = 0;
unsigned int flags = 0;
+ unsigned int dirty;
do {
struct page *page;
@@ -3216,6 +3233,7 @@ ssize_t generic_perform_write(struct file *file,
copied = iov_iter_copy_from_user_atomic(page, i, offset, bytes);
flush_dcache_page(page);
+ dirty = PageDirty(page);
status = a_ops->write_end(file, mapping, pos, bytes, copied,
page, fsdata);
if (unlikely(status < 0))
@@ -3241,7 +3259,7 @@ ssize_t generic_perform_write(struct file *file,
pos += copied;
written += copied;
- balance_dirty_pages_ratelimited(mapping);
+ __balance_dirty_pages_ratelimited(mapping, dirty);
} while (iov_iter_count(i));
return written ? written : status;
diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index 7d1010453fb9..694ede8783f3 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -20,6 +20,7 @@
#include <linux/slab.h>
#include <linux/pagemap.h>
#include <linux/writeback.h>
+#include <linux/fsio-throttle.h>
#include <linux/init.h>
#include <linux/backing-dev.h>
#include <linux/task_io_accounting_ops.h>
@@ -1858,10 +1859,12 @@ DEFINE_PER_CPU(int, dirty_throttle_leaks) = 0;
* limit we decrease the ratelimiting by a lot, to prevent individual processes
* from overshooting the limit by (ratelimit_pages) each.
*/
-void balance_dirty_pages_ratelimited(struct address_space *mapping)
+void __balance_dirty_pages_ratelimited(struct address_space *mapping,
+ bool redirty)
{
struct inode *inode = mapping->host;
struct backing_dev_info *bdi = inode_to_bdi(inode);
+ struct block_device *bdev = as_to_bdev(mapping);
struct bdi_writeback *wb = NULL;
int ratelimit;
int *p;
@@ -1878,6 +1881,13 @@ void balance_dirty_pages_ratelimited(struct address_space *mapping)
if (wb->dirty_exceeded)
ratelimit = min(ratelimit, 32 >> (PAGE_SHIFT - 10));
+ /*
+ * Throttle filesystem I/O only if page was initially clean: re-writing
+ * a dirty page doesn't generate additional I/O.
+ */
+ if (!redirty)
+ fsio_throttle(bdev_to_dev(bdev), PAGE_SIZE, TASK_KILLABLE);
+
preempt_disable();
/*
* This prevents one CPU to accumulate too many dirtied pages without
@@ -1911,7 +1921,7 @@ void balance_dirty_pages_ratelimited(struct address_space *mapping)
wb_put(wb);
}
-EXPORT_SYMBOL(balance_dirty_pages_ratelimited);
+EXPORT_SYMBOL(__balance_dirty_pages_ratelimited);
/**
* wb_over_bg_thresh - does @wb need to be written back?
--
2.17.1
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