From: NeilBrown <neilb@xxxxxxx>
Subject: mm/writeback: discard NR_UNSTABLE_NFS, use NR_WRITEBACK instead
After an NFS page has been written it is considered "unstable" until a
COMMIT request succeeds. If the COMMIT fails, the page will be
re-written.
These "unstable" pages are currently accounted as "reclaimable", either in
WB_RECLAIMABLE, or in NR_UNSTABLE_NFS which is included in a 'reclaimable'
count. This might have made sense when sending the COMMIT required a
separate action by the VFS/MM (e.g. releasepage() used to send a COMMIT).
However now that all writes generated by ->writepages() will
automatically be followed by a COMMIT (since commit 919e3bd9a875 ("NFS:
Ensure we commit after writeback is complete")) it makes more sense to
treat them as writeback pages.
So this patch removes NR_UNSTABLE_NFS and accounts unstable pages in
NR_WRITEBACK and WB_WRITEBACK.
A particular effect of this change is that when
wb_check_background_flush() calls wb_over_bg_threshold(), the latter will
report 'true' a lot less often as the 'unstable' pages are no longer
considered 'dirty' (as there is nothing that writeback can do about them
anyway).
Currently wb_check_background_flush() will trigger writeback to NFS even
when there are relatively few dirty pages (if there are lots of unstable
pages), this can result in small writes going to the server (10s of
Kilobytes rather than a Megabyte) which hurts throughput. With this
patch, there are fewer writes which are each larger on average.
Where the NR_UNSTABLE_NFS count was included in statistics virtual-files,
the entry is retained, but the value is hard-coded as zero. static trace
points and warning printks which mentioned this counter no longer report
it.
[akpm@xxxxxxxxxxxxxxxxxxxx: re-layout comment]
[akpm@xxxxxxxxxxxxxxxxxxxx: fix printk warning]
Link: http://lkml.kernel.org/r/87d06j7gqa.fsf@xxxxxxxxxxxxxxxxxxxxxxxx
Signed-off-by: NeilBrown <neilb@xxxxxxx>
Reviewed-by: Jan Kara <jack@xxxxxxx>
Reviewed-by: Christoph Hellwig <hch@xxxxxx>
Acked-by: Trond Myklebust <trond.myklebust@xxxxxxxxxxxxxxx>
Acked-by: Michal Hocko <mhocko@xxxxxxxx> [mm]
Cc: Christoph Hellwig <hch@xxxxxx>
Cc: Chuck Lever <chuck.lever@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
Documentation/filesystems/proc.rst | 4 ++--
drivers/base/node.c | 2 +-
fs/fs-writeback.c | 1 -
fs/nfs/internal.h | 10 +++++++---
fs/nfs/write.c | 4 ++--
fs/proc/meminfo.c | 3 +--
include/linux/mmzone.h | 1 -
include/trace/events/writeback.h | 5 +----
mm/memcontrol.c | 1 -
mm/page-writeback.c | 17 ++++-------------
mm/page_alloc.c | 5 +----
mm/vmstat.c | 11 +++++++++--
12 files changed, 28 insertions(+), 36 deletions(-)
--- a/Documentation/filesystems/proc.rst~mm-discard-nr_unstable_nfs-use-nr_writeback-instead
+++ a/Documentation/filesystems/proc.rst
@@ -1043,8 +1043,8 @@ PageTables
amount of memory dedicated to the lowest level of page
tables.
NFS_Unstable
- NFS pages sent to the server, but not yet committed to stable
- storage
+ Always zero. Previous counted pages which had been written to
+ the server, but has not been committed to stable storage.
Bounce
Memory used for block device "bounce buffers"
WritebackTmp
--- a/drivers/base/node.c~mm-discard-nr_unstable_nfs-use-nr_writeback-instead
+++ a/drivers/base/node.c
@@ -445,7 +445,7 @@ static ssize_t node_read_meminfo(struct
nid, sum_zone_node_page_state(nid, NR_KERNEL_SCS_KB),
#endif
nid, K(sum_zone_node_page_state(nid, NR_PAGETABLE)),
- nid, K(node_page_state(pgdat, NR_UNSTABLE_NFS)),
+ nid, 0UL,
nid, K(sum_zone_node_page_state(nid, NR_BOUNCE)),
nid, K(node_page_state(pgdat, NR_WRITEBACK_TEMP)),
nid, K(sreclaimable +
--- a/fs/fs-writeback.c~mm-discard-nr_unstable_nfs-use-nr_writeback-instead
+++ a/fs/fs-writeback.c
@@ -1070,7 +1070,6 @@ static void bdi_split_work_to_wbs(struct
static unsigned long get_nr_dirty_pages(void)
{
return global_node_page_state(NR_FILE_DIRTY) +
- global_node_page_state(NR_UNSTABLE_NFS) +
get_nr_dirty_inodes();
}
--- a/fs/nfs/internal.h~mm-discard-nr_unstable_nfs-use-nr_writeback-instead
+++ a/fs/nfs/internal.h
@@ -668,7 +668,8 @@ void nfs_super_set_maxbytes(struct super
}
/*
- * Record the page as unstable and mark its inode as dirty.
+ * Record the page as unstable (an extra writeback period) and mark its
+ * inode as dirty.
*/
static inline
void nfs_mark_page_unstable(struct page *page, struct nfs_commit_info *cinfo)
@@ -676,8 +677,11 @@ void nfs_mark_page_unstable(struct page
if (!cinfo->dreq) {
struct inode *inode = page_file_mapping(page)->host;
- inc_node_page_state(page, NR_UNSTABLE_NFS);
- inc_wb_stat(&inode_to_bdi(inode)->wb, WB_RECLAIMABLE);
+ /* This page is really still in write-back - just that the
+ * writeback is happening on the server now.
+ */
+ inc_node_page_state(page, NR_WRITEBACK);
+ inc_wb_stat(&inode_to_bdi(inode)->wb, WB_WRITEBACK);
__mark_inode_dirty(inode, I_DIRTY_DATASYNC);
}
}
--- a/fs/nfs/write.c~mm-discard-nr_unstable_nfs-use-nr_writeback-instead
+++ a/fs/nfs/write.c
@@ -946,9 +946,9 @@ nfs_mark_request_commit(struct nfs_page
static void
nfs_clear_page_commit(struct page *page)
{
- dec_node_page_state(page, NR_UNSTABLE_NFS);
+ dec_node_page_state(page, NR_WRITEBACK);
dec_wb_stat(&inode_to_bdi(page_file_mapping(page)->host)->wb,
- WB_RECLAIMABLE);
+ WB_WRITEBACK);
}
/* Called holding the request lock on @req */
--- a/fs/proc/meminfo.c~mm-discard-nr_unstable_nfs-use-nr_writeback-instead
+++ a/fs/proc/meminfo.c
@@ -110,8 +110,7 @@ static int meminfo_proc_show(struct seq_
show_val_kb(m, "PageTables: ",
global_zone_page_state(NR_PAGETABLE));
- show_val_kb(m, "NFS_Unstable: ",
- global_node_page_state(NR_UNSTABLE_NFS));
+ show_val_kb(m, "NFS_Unstable: ", 0);
show_val_kb(m, "Bounce: ",
global_zone_page_state(NR_BOUNCE));
show_val_kb(m, "WritebackTmp: ",
--- a/include/linux/mmzone.h~mm-discard-nr_unstable_nfs-use-nr_writeback-instead
+++ a/include/linux/mmzone.h
@@ -196,7 +196,6 @@ enum node_stat_item {
NR_FILE_THPS,
NR_FILE_PMDMAPPED,
NR_ANON_THPS,
- NR_UNSTABLE_NFS, /* NFS unstable pages */
NR_VMSCAN_WRITE,
NR_VMSCAN_IMMEDIATE, /* Prioritise for reclaim when writeback ends */
NR_DIRTIED, /* page dirtyings since bootup */
--- a/include/trace/events/writeback.h~mm-discard-nr_unstable_nfs-use-nr_writeback-instead
+++ a/include/trace/events/writeback.h
@@ -541,7 +541,6 @@ TRACE_EVENT(global_dirty_state,
TP_STRUCT__entry(
__field(unsigned long, nr_dirty)
__field(unsigned long, nr_writeback)
- __field(unsigned long, nr_unstable)
__field(unsigned long, background_thresh)
__field(unsigned long, dirty_thresh)
__field(unsigned long, dirty_limit)
@@ -552,7 +551,6 @@ TRACE_EVENT(global_dirty_state,
TP_fast_assign(
__entry->nr_dirty = global_node_page_state(NR_FILE_DIRTY);
__entry->nr_writeback = global_node_page_state(NR_WRITEBACK);
- __entry->nr_unstable = global_node_page_state(NR_UNSTABLE_NFS);
__entry->nr_dirtied = global_node_page_state(NR_DIRTIED);
__entry->nr_written = global_node_page_state(NR_WRITTEN);
__entry->background_thresh = background_thresh;
@@ -560,12 +558,11 @@ TRACE_EVENT(global_dirty_state,
__entry->dirty_limit = global_wb_domain.dirty_limit;
),
- TP_printk("dirty=%lu writeback=%lu unstable=%lu "
+ TP_printk("dirty=%lu writeback=%lu "
"bg_thresh=%lu thresh=%lu limit=%lu "
"dirtied=%lu written=%lu",
__entry->nr_dirty,
__entry->nr_writeback,
- __entry->nr_unstable,
__entry->background_thresh,
__entry->dirty_thresh,
__entry->dirty_limit,
--- a/mm/memcontrol.c~mm-discard-nr_unstable_nfs-use-nr_writeback-instead
+++ a/mm/memcontrol.c
@@ -4330,7 +4330,6 @@ void mem_cgroup_wb_stats(struct bdi_writ
*pdirty = memcg_exact_page_state(memcg, NR_FILE_DIRTY);
- /* this should eventually include NR_UNSTABLE_NFS */
*pwriteback = memcg_exact_page_state(memcg, NR_WRITEBACK);
*pfilepages = memcg_exact_page_state(memcg, NR_INACTIVE_FILE) +
memcg_exact_page_state(memcg, NR_ACTIVE_FILE);
--- a/mm/page_alloc.c~mm-discard-nr_unstable_nfs-use-nr_writeback-instead
+++ a/mm/page_alloc.c
@@ -5319,7 +5319,7 @@ void show_free_areas(unsigned int filter
printk("active_anon:%lu inactive_anon:%lu isolated_anon:%lu\n"
" active_file:%lu inactive_file:%lu isolated_file:%lu\n"
- " unevictable:%lu dirty:%lu writeback:%lu unstable:%lu\n"
+ " unevictable:%lu dirty:%lu writeback:%lu\n"
" slab_reclaimable:%lu slab_unreclaimable:%lu\n"
" mapped:%lu shmem:%lu pagetables:%lu bounce:%lu\n"
" free:%lu free_pcp:%lu free_cma:%lu\n",
@@ -5332,7 +5332,6 @@ void show_free_areas(unsigned int filter
global_node_page_state(NR_UNEVICTABLE),
global_node_page_state(NR_FILE_DIRTY),
global_node_page_state(NR_WRITEBACK),
- global_node_page_state(NR_UNSTABLE_NFS),
global_node_page_state(NR_SLAB_RECLAIMABLE),
global_node_page_state(NR_SLAB_UNRECLAIMABLE),
global_node_page_state(NR_FILE_MAPPED),
@@ -5365,7 +5364,6 @@ void show_free_areas(unsigned int filter
" anon_thp: %lukB"
#endif
" writeback_tmp:%lukB"
- " unstable:%lukB"
" all_unreclaimable? %s"
"\n",
pgdat->node_id,
@@ -5387,7 +5385,6 @@ void show_free_areas(unsigned int filter
K(node_page_state(pgdat, NR_ANON_THPS) * HPAGE_PMD_NR),
#endif
K(node_page_state(pgdat, NR_WRITEBACK_TEMP)),
- K(node_page_state(pgdat, NR_UNSTABLE_NFS)),
pgdat->kswapd_failures >= MAX_RECLAIM_RETRIES ?
"yes" : "no");
}
--- a/mm/page-writeback.c~mm-discard-nr_unstable_nfs-use-nr_writeback-instead
+++ a/mm/page-writeback.c
@@ -504,7 +504,6 @@ bool node_dirty_ok(struct pglist_data *p
unsigned long nr_pages = 0;
nr_pages += node_page_state(pgdat, NR_FILE_DIRTY);
- nr_pages += node_page_state(pgdat, NR_UNSTABLE_NFS);
nr_pages += node_page_state(pgdat, NR_WRITEBACK);
return nr_pages <= limit;
@@ -758,7 +757,7 @@ static void mdtc_calc_avail(struct dirty
* bounded by the bdi->min_ratio and/or bdi->max_ratio parameters, if set.
*
* Return: @wb's dirty limit in pages. The term "dirty" in the context of
- * dirty balancing includes all PG_dirty, PG_writeback and NFS unstable pages.
+ * dirty balancing includes all PG_dirty and PG_writeback pages.
*/
static unsigned long __wb_calc_thresh(struct dirty_throttle_control *dtc)
{
@@ -1566,7 +1565,7 @@ static void balance_dirty_pages(struct b
struct dirty_throttle_control * const mdtc = mdtc_valid(&mdtc_stor) ?
&mdtc_stor : NULL;
struct dirty_throttle_control *sdtc;
- unsigned long nr_reclaimable; /* = file_dirty + unstable_nfs */
+ unsigned long nr_reclaimable; /* = file_dirty */
long period;
long pause;
long max_pause;
@@ -1586,14 +1585,7 @@ static void balance_dirty_pages(struct b
unsigned long m_thresh = 0;
unsigned long m_bg_thresh = 0;
- /*
- * Unstable writes are a feature of certain networked
- * filesystems (i.e. NFS) in which data may have been
- * written to the server's write cache, but has not yet
- * been flushed to permanent storage.
- */
- nr_reclaimable = global_node_page_state(NR_FILE_DIRTY) +
- global_node_page_state(NR_UNSTABLE_NFS);
+ nr_reclaimable = global_node_page_state(NR_FILE_DIRTY);
gdtc->avail = global_dirtyable_memory();
gdtc->dirty = nr_reclaimable + global_node_page_state(NR_WRITEBACK);
@@ -1963,8 +1955,7 @@ bool wb_over_bg_thresh(struct bdi_writeb
* as we're trying to decide whether to put more under writeback.
*/
gdtc->avail = global_dirtyable_memory();
- gdtc->dirty = global_node_page_state(NR_FILE_DIRTY) +
- global_node_page_state(NR_UNSTABLE_NFS);
+ gdtc->dirty = global_node_page_state(NR_FILE_DIRTY);
domain_dirty_limits(gdtc);
if (gdtc->dirty > gdtc->bg_thresh)
--- a/mm/vmstat.c~mm-discard-nr_unstable_nfs-use-nr_writeback-instead
+++ a/mm/vmstat.c
@@ -1108,7 +1108,7 @@ int fragmentation_index(struct zone *zon
TEXT_FOR_HIGHMEM(xx) xx "_movable",
const char * const vmstat_text[] = {
- /* enum zone_stat_item countes */
+ /* enum zone_stat_item counters */
"nr_free_pages",
"nr_zone_inactive_anon",
"nr_zone_active_anon",
@@ -1165,7 +1165,6 @@ const char * const vmstat_text[] = {
"nr_file_hugepages",
"nr_file_pmdmapped",
"nr_anon_transparent_hugepages",
- "nr_unstable",
"nr_vmscan_write",
"nr_vmscan_immediate_reclaim",
"nr_dirtied",
@@ -1726,6 +1725,14 @@ static int vmstat_show(struct seq_file *
seq_puts(m, vmstat_text[off]);
seq_put_decimal_ull(m, " ", *l);
seq_putc(m, '\n');
+
+ if (off == NR_VMSTAT_ITEMS - 1) {
+ /*
+ * We've come to the end - add any deprecated counters to avoid
+ * breaking userspace which might depend on them being present.
+ */
+ seq_puts(m, "nr_unstable 0\n");
+ }
return 0;
}
_
